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Leaves
Leaves are palmately compound in mature trees, but seedlings and regenerating shoots may have simple leaves. The transition to compound leaves comes with age and may be gradual. Leaves have 5–11 leaflets, with the largest ones in the middle and may be stalkless or with short petioles. Leaflets may have toothed or smooth edges, and may be hairless or have simple-to-clumped hairs. Baobabs have stipules at the base of the leaves, but the stipules are soon shed in most species. Baobabs are deciduous, shedding leaves during the dry season.
Flowers
In most Adansonia species, the flowers are borne on short erect or spreading stalks in the axils of the leaves near the tips of reproductive shoots. Only A. digitata has flowers and fruits set on long, hanging stalks. There is usually only a single flower in an axil, but sometimes flowers occur in pairs. They are large, showy and strongly scented. They only open near dusk. Opening is rapid and movement of the flower parts is fast enough to be visible. Most Adansonia species are pollinated by bats. | Adansonia | Wikipedia | 238 | 563290 | https://en.wikipedia.org/wiki/Adansonia | Biology and health sciences | Others | null |
Flowers may remain attached to the trees for several days, but the reproductive phase is very short, with pollen shed during the first night and stigmas shriveled by the morning. The flower is made up of an outer 5-lobed calyx, and an inner ring of petals set around a fused tube of stamens. The outer lobes of the calyx are usually green (brown in A. grandidieri) and in bud are joined almost to the tip. As the flower opens, the calyx lobes split apart and become coiled or bent back (reflexed) at the base of the flower. The inner surface of the lobes are silky-hairy and cream, pink, or red. Sometimes the lobes do not separate cleanly, distorting the shape of the flower as they bend back. The calyx lobes remain fused at the base, leaving a feature (calyx tube) that has nectar-producing tissue and that is cup-shaped, flat or tubular; the form of the calyx tube varies with species. The flowers have a central tube (staminal tube) made up of fused stalks of stamens (filaments), with unfused filaments above. A densely hairy ovary is enclosed in the staminal tube, and a long style tipped with a stigma emerges from the filaments. Petals are set near the base of the staminal tube and are variable in shape and colour. The flowers, when fresh, may be white, cream, bright yellow or dark red, but fade quickly, often turning reddish when dried.
Fruit
The fruit of the baobabs is one of their distinguishing features. It is large, oval-to-round, and berry-like in most species (usually less than long in A. madagascariensis.). It has a dry, hard outer shell of variable thickness. In most species, the shell is indehiscent (does not break open easily). A. gibbosa is the only species with fruits that crack while still on the tree, which then tend to break open upon landing on the ground. Inside the outer shell, kidney-shaped seeds 10–15(−20) mm long are set in a dry pulp. | Adansonia | Wikipedia | 455 | 563290 | https://en.wikipedia.org/wiki/Adansonia | Biology and health sciences | Others | null |
Taxonomy
The earliest written reports of baobab are from a 14th-century travelogue by the Arab traveler Ibn Battuta. The first botanical description was in the De medicina Aegyptiorum by Prospero Alpini (1592), looking at fruits that he observed in Egypt from an unknown source. They were called Bahobab, possibly from the Arabic abū ḥibāb meaning "many-seeded fruit". The French explorer and botanist Michel Adanson (1727–1806) observed a baobab tree in 1749 on the island of Sor in Senegal, and wrote the first detailed botanical description of the full tree, accompanied with illustrations. Recognizing the connection to the fruit described by Alpini he called the genus Baobab. Linnaeus later renamed the genus Adansonia, to honour Adanson, but use of baobab as one of the common names has persisted. | Adansonia | Wikipedia | 185 | 563290 | https://en.wikipedia.org/wiki/Adansonia | Biology and health sciences | Others | null |
The genus Adansonia is in the subfamily Bombacoideae, within the family Malvaceae in the order Malvales. The subfamily Bombacoideae was previously treated as the Bombacaceae family but it is no longer recognized at the rank of family by the Angiosperm Phylogeny Group I 1998, II 2003 or the Kubitzki system 2003. There are eight accepted species of Adansonia. A new species (Adansonia kilima Pettigrew, et al.), was described in 2012, found in high-elevation sites in eastern and southern Africa. This, however, is no longer recognized as a distinct species but considered a synonym of A. digitata. Some high-elevation trees in Tanzania show different genetics and morphology, but further study is needed to determine if recognition of them as a separate species is warranted. The genus Adansonia is further divided into three sections. Section Adansonia includes only A. digitata. This species has hanging flowers and fruit, set on long flowering stalks. This is the type species for the genus Adansonia. All species of Adansonia except A. digitata are diploid; A. digitata is tetraploid. Section Brevitubae includes A. grandidieri and A. suarexensis. These are species with flower buds that set on short pedicles and that are approximately twice as long as wide. The other species are all classified within the section Longitubae. They also have flowers/fruits set on short pedicels, but the flower buds are five or more times as long as wide.
Species | Adansonia | Wikipedia | 339 | 563290 | https://en.wikipedia.org/wiki/Adansonia | Biology and health sciences | Others | null |
, there are eight recognized species of Adansonia, with six endemic to Madagascar, one native to mainland Africa and the Arabian Peninsula, and one native to Australia. The mainland African species (Adansonia digitata) also occurs on Madagascar, but it is not a native of that island. Baobabs were introduced in ancient times to south Asia and during the colonial era to the Caribbean. They are also present in the island nation of Cape Verde. A ninth species was described in 2012 (Adansonia kilima Pettigrew, et al.) but is no longer recognized as a distinct species. The African and Australian baobabs are similar in appearance, and the oldest splits within Adansonia are likely no older than 15 million years; thus, the Australian species represents a long-distance trans-oceanic dispersal event from Africa. The lineage leading to Adansonia was found to have diverged from its closest relatives in Bombacoideae like Ceiba /Chorisia at the end of the Eocene, during a time of abrupt global climate cooling and drying, while a divergence of this Adansonia+Ceiba /Chorisia clade from Pachira was found to be more ancient, dating to the middle Eocene.
Habitat
The Malagasy species are important components of the Madagascar dry deciduous forests. Within that biome, Adansonia madagascariensis and A. rubrostipa occur specifically in the Anjajavy Forest, sometimes growing out of the tsingy limestone itself. A. digitata has been called "a defining icon of African bushland". The tree also grows wild in Sudan in the regions of Darfur and the state of Kordofan. The locals call it "Gongolaze" and use its fruits as food and medicine and use the tree trunks as reservoirs to save water.
Ecology
Baobabs store water in the trunk (up to ) to endure harsh drought conditions. All occur in seasonally arid areas, and are deciduous, shedding their leaves during the dry season. Across Africa, the oldest and largest baobabs began to die in the early 21st century, likely from a combination of drought and rising temperatures. The trees appear to become parched, then become dehydrated and unable to support their massive trunks.
Baobabs are important as nest sites for birds, in particular the mottled spinetail and four species of weaver.
Notable trees | Adansonia | Wikipedia | 491 | 563290 | https://en.wikipedia.org/wiki/Adansonia | Biology and health sciences | Others | null |
Radiocarbon dating has provided data on a few individuals of A. digitata. The Panke baobab in Zimbabwe was some 2,450 years old when it died in 2011, making it the oldest angiosperm ever documented, and two other trees—Dorslandboom in Namibia and Glencoe in South Africa—were estimated to be approximately 2,000 years old. Another specimen known as Grootboom was dated and found to be at least 1,275 years old. The Glencoe Baobab, a specimen of A. digitata in Limpopo Province, South Africa, was considered to be the largest living individual, with a maximum circumference of and a diameter of about . The tree has since split into two parts, so the widest individual trunk may now be that of the Sunland Baobab, or Platland tree, also in South Africa. The diameter of this tree at ground level is and its circumference at breast height is .
Two large baobabs growing in Tsimanampetsotse National Park were also studied using radiocarbon dating. One called Grandmother is made up of three fused trunks of different ages, with the oldest part of the tree an estimated 1,600 years old. The second, "polygamous baobab", has six fused stems, and is an estimated 1,000 years old.
Culinary uses
Leaves
The tree's leaves may be eaten as a leaf vegetable.
Fruit
The white pith in the fruit of the Australian baobab (A. gregorii) tastes like sherbet. It has an acidic, tart, citrus flavor. It is a good source of vitamin C, potassium, carbohydrates, and phosphorus. The dried fruit powder of A. digitata, baobab powder, contains about 11% water, 80% carbohydrates (50% fiber), and modest levels of various nutrients, including riboflavin, calcium, magnesium, potassium, iron, and phytosterols, with low levels of protein and fats. Vitamin C content, described as variable in different samples, was in a range of per of dried powder. In 2008, baobab dried fruit pulp was authorized in the EU as a safe food ingredient, and later in the year was granted GRAS (generally recognized as safe) status in the United States. | Adansonia | Wikipedia | 489 | 563290 | https://en.wikipedia.org/wiki/Adansonia | Biology and health sciences | Others | null |
In Angola, the dry fruit of A. digitata is usually boiled, and the broth is used for juices or as the base for a type of ice cream known as gelado de múcua. In Zimbabwe, the fruit of A. digitata is eaten fresh or the crushed crumbly pulp is stirred into porridge and drinks. In Tanzania, the dry pulp of A. digitata is added to sugarcane to aid fermentation in brewing (beermaking).
Seed
The seeds of some species are a source of vegetable oil. The fruit pulp and seeds of A. grandidieri and A. za are eaten fresh.
Other uses
Some baobab species are sources of fiber, dye, and fuel. Indigenous Australians used the native species A. gregorii for several products, making string from the root fibers and decorative crafts from the fruits. Baobab oil from the seed is also used in cosmetics, particularly in moisturizers.
In culture
Baobab trees hold cultural and spiritual significance in many African societies. They are often the sites of communal gatherings, storytelling, and rituals. An unusual baobab was the namesake of Kukawa, formerly the capital of the Bornu Empire southwest of Lake Chad in Central Africa.
In the novel The Little Prince, the titular character takes care to root out baobabs that try to grow on his tiny planet home. The fearsome, grasping baobab trees, researchers have contended, were meant to represent Nazism attempting to destroy the planet.
Gallery | Adansonia | Wikipedia | 307 | 563290 | https://en.wikipedia.org/wiki/Adansonia | Biology and health sciences | Others | null |
A delimiter is a sequence of one or more characters for specifying the boundary between separate, independent regions in plain text, mathematical expressions or other data streams. An example of a delimiter is the comma character, which acts as a field delimiter in a sequence of comma-separated values. Another example of a delimiter is the time gap used to separate letters and words in the transmission of Morse code.
In mathematics, delimiters are often used to specify the scope of an operation, and can occur both as isolated symbols (e.g., colon in "") and as a pair of opposing-looking symbols (e.g., angled brackets in ).
Delimiters represent one of various means of specifying boundaries in a data stream. Declarative notation, for example, is an alternate method (without the use of delimiters) that uses a length field at the start of a data stream to specify the number of characters that the data stream contains.
Overview
Delimiters may be characterized as field and record delimiters, or as bracket delimiters.
Field and record delimiters
Field delimiters separate data fields. Record delimiters separate groups of fields.
For example, the CSV format uses a comma as the delimiter between fields, and an end-of-line indicator as the delimiter between records:
fname,lname,age,salary
nancy,davolio,33,$30000
erin,borakova,28,$25250
tony,raphael,35,$28700
This specifies a simple flat-file database table using the CSV file format.
Bracket delimiters
Bracket delimiters, also called block delimiters, region delimiters, or balanced delimiters, mark both the start and end of a region of text.
Common examples of bracket delimiters include:
Conventions
Historically, computing platforms have used certain delimiters by convention. The following tables depict a few examples for comparison.
Programming languages
( | Delimiter | Wikipedia | 416 | 564276 | https://en.wikipedia.org/wiki/Delimiter | Technology | Programming languages | null |
An expression vector, otherwise known as an expression construct, is usually a plasmid or virus designed for gene expression in cells. The vector is used to introduce a specific gene into a target cell, and can commandeer the cell's mechanism for protein synthesis to produce the protein encoded by the gene. Expression vectors are the basic tools in biotechnology for the production of proteins.
The vector is engineered to contain regulatory sequences that act as enhancer and promoter regions and lead to efficient transcription of the gene carried on the expression vector. The goal of a well-designed expression vector is the efficient production of protein, and this may be achieved by the production of significant amount of stable messenger RNA, which can then be translated into protein. The expression of a protein may be tightly controlled, and the protein is only produced in significant quantity when necessary through the use of an inducer. In some systems, however, the protein may be expressed constitutively. Escherichia coli is commonly used as the host for protein production, but other cell types may also be used. An example of the use of expression vector is the production of insulin, which is used for medical treatments of diabetes.
Elements
An expression vector has features that any vector may have, such as an origin of replication, a selectable marker, and a suitable site for the insertion of a gene like the multiple cloning site. The cloned gene may be transferred from a specialized cloning vector to an expression vector, although it is possible to clone directly into an expression vector. The cloning process is normally performed in Escherichia coli. Vectors used for protein production in organisms other than E.coli may have, in addition to a suitable origin of replication for its propagation in E. coli, elements that allow them to be maintained in another organism, and these vectors are called shuttle vectors.
Elements for expression
An expression vector must have elements necessary for gene expression. These may include a promoter, the correct translation initiation sequence such as a ribosomal binding site and start codon, a termination codon, and a transcription termination sequence. There are differences in the machinery for protein synthesis between prokaryotes and eukaryotes, therefore the expression vectors must have the elements for expression that are appropriate for the chosen host. For example, prokaryotes expression vectors would have a Shine-Dalgarno sequence at its translation initiation site for the binding of ribosomes, while eukaryotes expression vectors would contain the Kozak consensus sequence. | Expression vector | Wikipedia | 505 | 564380 | https://en.wikipedia.org/wiki/Expression%20vector | Biology and health sciences | Molecular biology | Biology |
The promoter initiates the transcription and is therefore the point of control for the expression of the cloned gene. The promoters used in expression vector are normally inducible, meaning that protein synthesis is only initiated when required by the introduction of an inducer such as IPTG. Gene expression however may also be constitutive (i.e. protein is constantly expressed) in some expression vectors. Low level of constitutive protein synthesis may occur even in expression vectors with tightly controlled promoters.
Protein tags
After the expression of the gene product, it may be necessary to purify the expressed protein; however, separating the protein of interest from the great majority of proteins of the host cell can be a protracted process. To make this purification process easier, a purification tag may be added to the cloned gene. This tag could be histidine (His) tag, other marker peptides, or a fusion partners such as glutathione S-transferase or maltose-binding protein. Some of these fusion partners may also help to increase the solubility of some expressed proteins. Other fusion proteins such as green fluorescent protein may act as a reporter gene for the identification of successful cloned genes, or they may be used to study protein expression in cellular imaging.
Other Elements
The expression vector is transformed or transfected into the host cell for protein synthesis. Some expression vectors may have elements for transformation or the insertion of DNA into the host chromosome, for example the vir genes for plant transformation, and integrase sites for chromosomal integration .
Some vectors may include targeting sequence that may target the expressed protein to a specific location such as the periplasmic space of bacteria.
Expression/Production systems
Different organisms may be used to express a gene's target protein, and the expression vector used will therefore have elements specific for use in the particular organism. The most commonly used organism for protein production is the bacterium Escherichia coli. However, not all proteins can be successfully expressed in E. coli, or be expressed with the correct form of post-translational modifications such as glycosylations, and other systems may therefore be used.
Bacterial | Expression vector | Wikipedia | 440 | 564380 | https://en.wikipedia.org/wiki/Expression%20vector | Biology and health sciences | Molecular biology | Biology |
The expression host of choice for the expression of many proteins is Escherichia coli as the production of heterologous protein in E. coli is relatively simple and convenient, as well as being rapid and cheap. A large number of E. coli expression plasmids are also available for a wide variety of needs. Other bacteria used for protein production include Bacillus subtilis.
Most heterologous proteins are expressed in the cytoplasm of E. coli. However, not all proteins formed may be soluble in the cytoplasm, and incorrectly folded proteins formed in cytoplasm can form insoluble aggregates called inclusion bodies. Such insoluble proteins will require refolding, which can be an involved process and may not necessarily produce high yield. Proteins which have disulphide bonds are often not able to fold correctly due to the reducing environment in the cytoplasm which prevents such bond formation, and a possible solution is to target the protein to the periplasmic space by the use of an N-terminal signal sequence. Another possibility is to manipulate the redox environment of the cytoplasm. Other more sophisticated systems are also being developed; such systems may allow for the expression of proteins previously thought impossible in E. coli, such as glycosylated proteins.
The promoters used for these vector are usually based on the promoter of the lac operon or the T7 promoter, and they are normally regulated by the lac operator. These promoters may also be hybrids of different promoters, for example, the Tac-Promoter is a hybrid of trp and lac promoters. Note that most commonly used lac or lac-derived promoters are based on the lacUV5 mutant which is insensitive to catabolite repression. This mutant allows for expression of protein under the control of the lac promoter when the growth medium contains glucose since glucose would inhibit gene expression if wild-type lac promoter is used. Presence of glucose nevertheless may still be used to reduce background expression through residual inhibition in some systems.
Examples of E. coli expression vectors are the pGEX series of vectors where glutathione S-transferase is used as a fusion partner and gene expression is under the control of the tac promoter, and the pET series of vectors which uses a T7 promoter. | Expression vector | Wikipedia | 476 | 564380 | https://en.wikipedia.org/wiki/Expression%20vector | Biology and health sciences | Molecular biology | Biology |
It is possible to simultaneously express two or more different proteins in E. coli using different plasmids. However, when 2 or more plasmids are used, each plasmid needs to use a different antibiotic selection as well as a different origin of replication, otherwise one of the plasmids may not be stably maintained. Many commonly used plasmids are based on the ColE1 replicon and are therefore incompatible with each other; in order for a ColE1-based plasmid to coexist with another in the same cell, the other would need to be of a different replicon, e.g. a p15A replicon-based plasmid such as the pACYC series of plasmids. Another approach would be to use a single two-cistron vector or design the coding sequences in tandem as a bi- or poly-cistronic construct.
Yeast
A yeast commonly used for protein production is Pichia pastoris. Examples of yeast expression vector in Pichia are the pPIC series of vectors, and these vectors use the AOX1 promoter which is inducible with methanol. The plasmids may contain elements for insertion of foreign DNA into the yeast genome and signal sequence for the secretion of expressed protein. Proteins with disulphide bonds and glycosylation can be efficiently produced in yeast. Another yeast used for protein production is Kluyveromyces lactis and the gene is expressed, driven by a variant of the strong lactase LAC4 promoter.
Saccharomyces cerevisiae is particularly widely used for gene expression studies in yeast, for example in yeast two-hybrid system for the study of protein-protein interaction. The vectors used in yeast two-hybrid system contain fusion partners for two cloned genes that allow the transcription of a reporter gene when there is interaction between the two proteins expressed from the cloned genes. | Expression vector | Wikipedia | 401 | 564380 | https://en.wikipedia.org/wiki/Expression%20vector | Biology and health sciences | Molecular biology | Biology |
Baculovirus
Baculovirus, a rod-shaped virus which infects insect cells, is used as the expression vector in this system. Insect cell lines derived from Lepidopterans (moths and butterflies), such as Spodoptera frugiperda, are used as host. A cell line derived from the cabbage looper is of particular interest, as it has been developed to grow fast and without the expensive serum normally needed to boost cell growth. The shuttle vector is called bacmid, and gene expression is under the control of a strong promoter pPolh. Baculovirus has also been used with mammalian cell lines in the BacMam system.
Baculovirus is normally used for production of glycoproteins, although the glycosylations may be different from those found in vertebrates. In general, it is safer to use than mammalian virus as it has a limited host range and does not infect vertebrates without modifications.
Plant
Many plant expression vectors are based on the Ti plasmid of Agrobacterium tumefaciens. In these expression vectors, DNA to be inserted into plant is cloned into the T-DNA, a stretch of DNA flanked by a 25-bp direct repeat sequence at either end, and which can integrate into the plant genome. The T-DNA also contains the selectable marker. The Agrobacterium provides a mechanism for transformation, integration of into the plant genome, and the promoters for its vir genes may also be used for the cloned genes. Concerns over the transfer of bacterial or viral genetic material into the plant however have led to the development of vectors called intragenic vectors whereby functional equivalents of plant genome are used so that there is no transfer of genetic material from an alien species into the plant.
Plant viruses may be used as vectors since the Agrobacterium method does not work for all plants. Examples of plant virus used are the tobacco mosaic virus (TMV), potato virus X, and cowpea mosaic virus. The protein may be expressed as a fusion to the coat protein of the virus and is displayed on the surface of assembled viral particles, or as an unfused protein that accumulates within the plant. Expression in plant using plant vectors is often constitutive, and a commonly used constitutive promoter in plant expression vectors is the cauliflower mosaic virus (CaMV) 35S promoter. | Expression vector | Wikipedia | 503 | 564380 | https://en.wikipedia.org/wiki/Expression%20vector | Biology and health sciences | Molecular biology | Biology |
Mammalian
Mammalian expression vectors offer considerable advantages for the expression of mammalian proteins over bacterial expression systems - proper folding, post-translational modifications, and relevant enzymatic activity. It may also be more desirable than other eukaryotic non-mammalian systems whereby the proteins expressed may not contain the correct glycosylations. It is of particular use in producing membrane-associating proteins that require chaperones for proper folding and stability as well as containing numerous post-translational modifications. The downside, however, is the low yield of product in comparison to prokaryotic vectors as well as the costly nature of the techniques involved. Its complicated technology, and potential contamination with animal viruses of mammalian cell expression have also placed a constraint on its use in large-scale industrial production.
Cultured mammalian cell lines such as the Chinese hamster ovary (CHO), COS, including human cell lines such as HEK and HeLa may be used to produce protein. Vectors are transfected into the cells and the DNA may be integrated into the genome by homologous recombination in the case of stable transfection, or the cells may be transiently transfected. Examples of mammalian expression vectors include the adenoviral vectors, the pSV and the pCMV series of plasmid vectors, vaccinia and retroviral vectors, as well as baculovirus. The promoters for cytomegalovirus (CMV) and SV40 are commonly used in mammalian expression vectors to drive gene expression. Non-viral promoter, such as the elongation factor (EF)-1 promoter, is also known.
Cell-free systems
E. coli cell lysate containing the cellular components required for transcription and translation are used in this in vitro method of protein production. The advantage of such system is that protein may be produced much faster than those produced in vivo since it does not require time to culture the cells, but it is also more expensive. Vectors used for E. coli expression can be used in this system although specifically designed vectors for this system are also available. Eukaryotic cell extracts may also be used in other cell-free systems, for example, the wheat germ cell-free expression systems. Mammalian cell-free systems have also been produced.
Applications | Expression vector | Wikipedia | 471 | 564380 | https://en.wikipedia.org/wiki/Expression%20vector | Biology and health sciences | Molecular biology | Biology |
Laboratory use
Expression vector in an expression host is now the usual method used in laboratories to produce proteins for research. Most proteins are produced in E. coli, but for glycosylated proteins and those with disulphide bonds, yeast, baculovirus and mammalian systems may be used.
Production of peptide and protein pharmaceuticals
Most protein pharmaceuticals are now produced through recombinant DNA technology using expression vectors. These peptide and protein pharmaceuticals may be hormones, vaccines, antibiotics, antibodies, and enzymes. The first human recombinant protein used for disease management, insulin, was introduced in 1982. Biotechnology allows these peptide and protein pharmaceuticals, some of which were previously rare or difficult to obtain, to be produced in large quantity. It also reduces the risks of contaminants such as host viruses, toxins and prions. Examples from the past include prion contamination in growth hormone extracted from pituitary glands harvested from human cadavers, which caused Creutzfeldt–Jakob disease in patients receiving treatment for dwarfism, and viral contaminants in clotting factor VIII isolated from human blood that resulted in the transmission of viral diseases such as hepatitis and AIDS. Such risk is reduced or removed completely when the proteins are produced in non-human host cells.
Transgenic plant and animals
In recent years, expression vectors have been used to introduce specific genes into plants and animals to produce transgenic organisms, for example in agriculture it is used to produce transgenic plants. Expression vectors have been used to introduce a vitamin A precursor, beta-carotene, into rice plants. This product is called golden rice. This process has also been used to introduce a gene into plants that produces an insecticide, called Bacillus thuringiensis toxin or Bt toxin which reduces the need for farmers to apply insecticides since it is produced by the modified organism. In addition expression vectors are used to extend the ripeness of tomatoes by altering the plant so that it produces less of the chemical that causes the tomatoes to rot. There have been controversies over using expression vectors to modify crops due to the fact that there might be unknown health risks, possibilities of companies patenting certain genetically modified food crops, and ethical concerns. Nevertheless, this technique is still being used and heavily researched. | Expression vector | Wikipedia | 460 | 564380 | https://en.wikipedia.org/wiki/Expression%20vector | Biology and health sciences | Molecular biology | Biology |
Transgenic animals have also been produced to study animal biochemical processes and human diseases, or used to produce pharmaceuticals and other proteins. They may also be engineered to have advantageous or useful traits. Green fluorescent protein is sometimes used as tags which results in animal that can fluoresce, and this have been exploited commercially to produce the fluorescent GloFish.
Gene therapy
Gene therapy is a promising treatment for a number of diseases where a "normal" gene carried by the vector is inserted into the genome, to replace an "abnormal" gene or supplement the expression of particular gene. Viral vectors are generally used but other nonviral methods of delivery are being developed. The treatment is still a risky option due to the viral vector used which can cause ill-effects, for example giving rise to insertional mutation that can result in cancer. However, there have been promising results. | Expression vector | Wikipedia | 174 | 564380 | https://en.wikipedia.org/wiki/Expression%20vector | Biology and health sciences | Molecular biology | Biology |
A clock face is the part of an analog clock (or watch) that displays time through the use of a flat dial with reference marks, and revolving pointers turning on concentric shafts at the center, called hands. In its most basic, globally recognized form, the periphery of the dial is numbered 1 through 12 indicating the hours in a 12-hour cycle, and a short hour hand makes two revolutions in a day. A long minute hand makes one revolution every hour. The face may also include a second hand, which makes one revolution per minute. The term is less commonly used for the time display on digital clocks and watches.
A second type of clock face is the 24-hour analog dial, widely used in military and other organizations that use 24-hour time. This is similar to the 12-hour dial above, except it has hours numbered 1–24 (or 0–23) around the outside, and the hour hand makes only one revolution per day. Some special-purpose clocks, such as timers and sporting event clocks, are designed for measuring periods less than one hour. Clocks can indicate the hour with Roman numerals or Hindu–Arabic numerals, or with non-numeric indicator marks. The two numbering systems have also been used in combination, with the prior indicating the hour and the latter the minute. Longcase clocks (grandfather clocks) typically use Roman numerals for the hours. Clocks using only Arabic numerals first began to appear in the mid-18th century.
The clock face is so familiar that the numbers are often omitted and replaced with unlabeled graduations (marks), particularly in the case of watches. Occasionally, markings of any sort are dispensed with, and the time is read by the angles of the hands.
Reading a modern clock face
Most modern clocks have the numbers 1 through 12 printed at equally spaced intervals around the periphery of the face with the 12 at the top, indicating the hour, and on many models, sixty dots or lines evenly spaced in a ring around the outside of the dial, indicating minutes and seconds. The time is read by observing the placement of several "hands", which emanate from the centre of the dial:
A short, thick "hour" hand;
A long, thinner "minute" hand;
On some models, a very thin "second" or "sweep" hand
All three hands continuously rotate around the dial in a clockwise direction – in the direction of increasing numbers. | Clock face | Wikipedia | 502 | 564384 | https://en.wikipedia.org/wiki/Clock%20face | Technology | Clocks | null |
The second, or sweep, hand moves relatively quickly, taking a full minute (sixty seconds) to make a complete rotation from 12 to 12. For every rotation of the second hand, the minute hand will move from one minute mark to the next.
The minute hand rotates more slowly around the dial. It takes one hour (sixty minutes) to make a complete rotation from 12 to 12. For every rotation of the minute hand, the hour hand will move from one hour mark to the next.
The hour hand moves slowest of all, taking half a day (twelve hours) to make a complete rotation. It starts from "12" at midnight, makes one rotation until it is pointing at "12" again at noon, and then makes another rotation until it is pointing at "12" again at midnight of the next morning.
Historical development
The word clock derives from the medieval Latin word for "bell"; , and has cognates in many European languages. Clocks spread to England from the Low Countries, so the English word came from the Middle Low German and Middle Dutch Klocke. The first mechanical clocks, built in 13th-century Europe, were striking clocks: their purpose was to ring bells upon the canonical hours, to call the local community to prayer. These were tower clocks installed in bell towers in public places, to ensure that the bells were audible over a wide area. Soon after these first mechanical clocks were in place clockmakers realized that their wheels could be used to drive an indicator on a dial on the outside of the tower, where it could be widely seen, so the local population could tell the time between the hourly strikes. | Clock face | Wikipedia | 332 | 564384 | https://en.wikipedia.org/wiki/Clock%20face | Technology | Clocks | null |
Before the late 14th century, a fixed hand (often a carving literally shaped like a hand) indicated the hour by pointing to numbers on a rotating dial; after this time, the current convention of a rotating hand on a fixed dial was adopted. Minute hands (so named because they indicated the small, or minute, divisions of the hour) only came into regular use around 1690, after the invention of the pendulum and anchor escapement increased the precision of time-telling enough to justify it. In some precision clocks, a third hand, which rotated once a minute, was added in a separate subdial. This was called the "second-minute" hand (because it measured the secondary minute divisions of the hour), which was shortened to "second" hand. The convention of the hands moving clockwise evolved in imitation of the sundial. In the Northern hemisphere, where the clock face originated, the shadow of the gnomon on a horizontal sundial moves clockwise during the day.
French decimal time
During the French Revolution in 1793, in connection with its Republican calendar, France attempted to introduce a decimal time system. This had 10 decimal hours in the day, 100 decimal minutes per hour, and 100 decimal seconds per minute. Therefore, the decimal hour was more than twice as long (144 min) as the present hour, the decimal minute was slightly longer than the present minute (86.4 seconds) and the decimal second was slightly shorter (0.864 sec) than the present second. Clocks were manufactured with this alternate face, usually combined with traditional hour markings. However, it did not catch on, and France discontinued the mandatory use of decimal time on 7 April 1795, although some French cities used decimal time until 1801.
Stylistic development
Until the last quarter of the 17th century, hour markings were etched into metal faces and the recesses filled with black wax. Subsequently, higher contrast and improved readability was achieved with white enamel plaques painted with black numbers. Initially, the numbers were printed on small, individual plaques mounted on a brass substructure. This was not a stylistic decision, rather enamel production technology had not yet achieved the ability to create large pieces of enamel. The "13-piece face" was an early attempt to create an entirely white enamel face. As the name suggests, it was composed of 13 enamel plaques: 12 numbered wedges fitted around a circle. The first single-piece enamel faces, not unlike those in production today, began to appear . | Clock face | Wikipedia | 497 | 564384 | https://en.wikipedia.org/wiki/Clock%20face | Technology | Clocks | null |
It is customary for modern advertisements to display clocks and watches set to approximately 10:10 or 1:50,
as this V-shaped arrangement roughly makes a smile, imitates a human figure with raised arms, and leaves the watch company's logo unobscured by the hands.
In the 1970s, German designer Tian Harlan invented the Chromachron, a wristwatch with a clock face that has no dials but a disc with pie-shaped pattern rotating by the minute over color patterns representing both hours and minutes.
Technological obsolescence
In the 2010s, some United Kingdom schools started replacing analogue clocks in examination halls with digital clocks because an increasing number of pupils were unable to read analogue clocks. Smartphone and computer clocks are often digital rather than analogue, and proponents of replacing analogue clock faces argue that they have become technologically obsolete. However, reading analogue clocks is still part of American elementary school curricula; proponents of analogue clocks argue that their inclusion in the curriculum reinforces basic mathematical concepts that are taught in elementary school. | Clock face | Wikipedia | 207 | 564384 | https://en.wikipedia.org/wiki/Clock%20face | Technology | Clocks | null |
The African buffalo (Syncerus caffer) is a large sub-Saharan African bovine. There are five subspecies that are recognized as valid by most authorities:
Syncerus caffer caffer, the Cape buffalo, is the nominotypical subspecies, as well as the largest, found in Southern and East Africa.
S. c. nanus, the forest buffalo, is the smallest subspecies, common in forest areas of Central and West Africa
S. c. brachyceros, the Sudan buffalo, a smaller version of the Cape buffalo, found in the drier, northern areas of Central and West Africa.
S. c. aequinoctialis, the Nile Buffalo, sometimes considered identical to the Sudan buffalo, found in the drier, northern areas of East and Central Africa.
S. c. mathewsi, the mountain buffalo, a disputed subspecies from the Virunga Mountains in Central Africa.
The adult African buffalo's horns are its characteristic feature: they have fused bases, forming a continuous bone shield across the top of the head, referred to as a "boss".
The African buffalo is more closely related to other buffalo species than it is to other bovids such as American bison or domestic cattle, with its closest living relative being the Asian water buffalo. Its unpredictable temperament may be part of the reason that the African buffalo has never been domesticated, which would also explain why the African buffalo has no domesticated descendants, unlike the wild yak and wild water buffalo which are the ancestors of the domestic yak and water buffalo. Natural predators of adult African buffaloes include lions, African wild dogs, spotted hyenas, and Nile crocodiles. As one of the Big Five game animals, the Cape buffalo is a sought-after trophy in hunting.
Description | African buffalo | Wikipedia | 361 | 564971 | https://en.wikipedia.org/wiki/African%20buffalo | Biology and health sciences | Artiodactyla | null |
The African buffalo is a very robust species. Its shoulder height can range from and its head-and-body length can range from . The tail can range from long. Compared with other large bovids, it has a long but stocky body (the body length can exceed the wild water buffalo, which is heavier and taller) and short but thickset legs, resulting in a relatively short standing height. Cape buffaloes weigh (males weigh about more than females). In comparison, African forest buffaloes, at , are only half that size. Its head is carried low; its top is located below the backline. The front hooves of the buffalo are wider than the rear, which is associated with the need to support the weight of the front part of the body, which is heavier and more powerful than the back.
Savannah-type buffaloes have black or dark brown coats with age. Old bulls often have whitish circles around their eyes and on their face. Females tend to have more reddish coats. Forest-type buffaloes are 30–40% smaller, reddish brown in colour, with much more hair growth around the ears and with horns that curve back and slightly up. Calves of both types have red coats.
A characteristic feature of the horns of adult male African buffalo (southern and eastern populations) is that the bases come very close together, forming a shield referred to as a "boss". From the base, the horns diverge downwards, then smoothly curve upwards and outwards and in some cases inwards and or backwards. In large bulls, the distance between the ends of the horns can reach upwards of one metre (the record being 64.5 inches 164 cm). The horns form fully when the animal reaches the age of 5 or 6 years old, but the bosses do not become "hard" until it reaches the age of 8 to 9 years old. In cows, the horns are, on average, 10–20% smaller, and they do not have a boss. Forest-type buffalo horns are smaller than those of the savanna-type buffaloes from Southern and East Africa, usually measuring less than , and are almost never fused.
Unlike other large bovines, African buffalo have 52 chromosomes (for comparison, American bison and domestic cattle have 60). This means domestic cattle and bison are unable to create hybrid offspring with cape buffalo.
Subspecies | African buffalo | Wikipedia | 476 | 564971 | https://en.wikipedia.org/wiki/African%20buffalo | Biology and health sciences | Artiodactyla | null |
Ecology
The African buffalo is one of the most successful grazers in Africa. It lives in savannas, swamps and floodplains, as well as mopane grasslands, and the forests of the major mountains of Africa. This buffalo prefers a habitat with dense cover, such as reeds and thickets, but can also be found in open woodland. While not particularly demanding in regard to habitat, they require water daily, and so they depend on perennial sources of water. Like the plains zebra, the buffalo can live on tall, coarse grasses. Herds of buffalo mow down grasses and make way for more selective grazers. When feeding, the buffalo makes use of its tongue and wide incisor row to eat grass more quickly than most other African herbivores. Buffaloes do not stay on trampled or depleted areas for long. | African buffalo | Wikipedia | 169 | 564971 | https://en.wikipedia.org/wiki/African%20buffalo | Biology and health sciences | Artiodactyla | null |
Other than humans, African buffaloes have few predators and are capable of defending themselves against (and killing) lions. Lions kill and eat buffaloes regularly, and in some regions, the buffaloes are the lions' primary prey. It often takes several lions to bring down a single adult buffalo, and the entire pride may join in the hunt. However, several incidents have been reported in which lone adult male lions have successfully brought down adult buffaloes. On very rare occasions, buffaloes and white rhinos will fight over territory; due to the rhino's strength and size advantage, the rhino typically wins and the buffalo can die from injuries sustained during the encounter. Rhinos live solitary lives, whereas buffalo (excluding solitary adult bulls) primarily live social lives and thus they do not usually recognize each other as threats. Hippopotamuses and buffalo also do not normally interact, but if the buffalo provokes the hippo or makes it feel threatened, a fight can break out, but this is also rare. Adolescent bull African elephants may harass or kill Cape buffalo, either out of territorial aggression or while in musth; when they do this, the calves are most likely to be killed by the elephant attack as they are defenseless when facing an elephant alone, whereas adults will try to fight back and may survive (or succumb to injuries afterward). The average-sized Nile crocodile typically attacks only old solitary animals and young calves, though they can kill healthy adults. Exceptionally large, old male crocodiles may become semi-habitual predators of buffaloes. The cheetah, leopard, African wild dog and spotted hyena are normally a threat only to newborn calves, though larger clans of hyenas have been recorded killing cows (mainly pregnant ones) and, on rare occasions, full-grown bulls. Large packs of wild dogs have been observed to hunt calves and sick adults.
Diseases | African buffalo | Wikipedia | 383 | 564971 | https://en.wikipedia.org/wiki/African%20buffalo | Biology and health sciences | Artiodactyla | null |
The African buffalo is susceptible to many diseases, including those shared with domestic cattle, such as bovine tuberculosis, corridor disease, and foot-and-mouth disease. As with many diseases, these problems remain dormant within a population as long as the health of the animals is good. These diseases do, however, restrict the legal movements of the animals and fencing infected areas from unaffected areas is enforced. Some wardens and game managers have managed to protect and breed "disease-free" herds which become very valuable because they can be transported. Most well-known are Lindsay Hunt's efforts to source uninfected animals from the Kruger National Park in South Africa. Some disease-free buffaloes in South Africa have been sold to breeders for close to US$130,000.
Social behavior
Herd size is highly variable. The core of the herds is made up of related females, and their offspring, in an almost linear dominance hierarchy. The basic herds are surrounded by subherds of subordinate males, high-ranking males and females, and old or invalid animals.
African buffaloes engage in several types of group behavior. Females appear to exhibit a sort of "voting behavior". During resting time, the females stand up, shuffle around, and sit back down again. They sit in the direction they think they should move. After an hour of more shuffling, the females travel in the direction they decide. This decision is communal and not based on hierarchy or dominance.
When chased by predators, a herd sticks close together and makes it hard for the predators to pick off one member. Calves are gathered in the middle. A buffalo herd responds to the distress call of a threatened member and tries to rescue it. A calf's distress call gets the attention of not only the mother, but also the herd. Buffaloes engage in mobbing behavior when fighting off predators. They have been recorded killing lions and chasing lions up trees and keeping them there for two hours, after the lions have killed a member of their group. Lion cubs can get trampled and killed. In one videotaped instance, known as the Battle at Kruger, a calf survived an attack by both lions and a crocodile after intervention of the herd.
Males have a linear dominance hierarchy based on age and size. Since a buffalo is safer when a herd is larger, dominant bulls may rely on subordinate bulls and sometimes tolerate their copulation. The young males keep their distance from the dominant bull, which is recognizable by the thickness of his horns. | African buffalo | Wikipedia | 501 | 564971 | https://en.wikipedia.org/wiki/African%20buffalo | Biology and health sciences | Artiodactyla | null |
Adult bulls spar in play, dominance interactions, or actual fights. A bull approaches another, lowing, with his horns down, and waits for the other bull to do the same thing. When sparring, the bulls twist their horns from side to side. If the sparring is for play, the bull may rub his opponent's face and body during the sparring session. Actual fights are violent but rare and brief. Calves may also spar in play, but adult females rarely spar at all.
During the dry season, males split from the herd and form bachelor groups. Two types of bachelor herds occur: ones made of males aged four to seven years and those of males 12 years or older. During the wet season, the younger bulls rejoin a herd to mate with the females. They stay with them throughout the season to protect the calves. Some older bulls cease to rejoin the herd, as they can no longer compete with the younger, more aggressive males. The old bachelors are called dagga boys ("mud covered"), and are considered the most dangerous to humans.
Vocalizations
African buffaloes make various vocalizations. Many calls are lower-pitched versions of those emitted by domestic cattle. They emit low-pitched, two- to four-second calls intermittently at three- to six-second intervals to signal the herd to move. To signal to the herd to change direction, leaders emit "gritty", "creaking gate" sounds. When moving to drinking places, some individuals make long "maaa" calls up to 20 times a minute. When being aggressive, they make explosive grunts that may last long or turn into a rumbling growl. Cows produce croaking calls when looking for their calves. Calves make a similar call of a higher pitch when in distress. When threatened by predators, they make drawn-out "waaaa" calls. Dominant individuals make calls to announce their presence and location. A version of the same call, but more intense, is emitted as a warning to an encroaching inferior. When grazing, they make various sounds, such as brief bellows, grunts, honks, and croaks.
Reproduction | African buffalo | Wikipedia | 446 | 564971 | https://en.wikipedia.org/wiki/African%20buffalo | Biology and health sciences | Artiodactyla | null |
Females reach sexual maturity at around five years of age while males are sexually matured at four to six. African buffaloes mate and give birth only during the rainy seasons. Birth peak takes place early in the season, while mating peaks later. A bull closely guards a cow that comes into heat, while keeping other bulls at bay. This is difficult, as cows are quite evasive and attract many males to the scene. By the time a cow is in full estrus, only the most dominant bull in the herd/subherd is there.
Cows first calve at five years of age, after a gestation period of 11.5 months. Newborn calves remain hidden in vegetation for the first few weeks while being nursed occasionally by the mother before joining the main herd. Older calves are held in the centre of the herd for safety. The maternal bond between mother and calf lasts longer than in most bovids. That bonding ends when a new calf is born, and the mother then keeps her previous offspring at bay with horn jabs. Nevertheless, the yearling follows its mother for another year or so. Males leave their mothers when they are two years old and join the bachelor groups. Young calves, unusually for bovids, suckle from behind their mothers, pushing their heads between the mothers' legs.
In the wild African buffaloes have an average lifespan of 11 years but they've been recorded to reach 22 years of age. In captivity they can live for a maximum of 29.5 years though they only live 16 years on average.
Relationship with humans
Status
The current status of the African buffalo is dependent on the animal's value to both trophy hunters and tourists, paving the way for conservation efforts through anti-poaching patrols, village crop damage payouts, and CAMPFIRE payback programs to local areas.
The African buffalo is listed as Near threatened by the IUCN, with a decreasing population of 400,000 individuals. While some populations (subspecies) are decreasing, others will remain unchanged in the long term if large, healthy populations continue to persist in a substantial number of national parks, equivalent reserves and hunting zones in southern and eastern Africa."
In the most recent and available census data at continental scale, the total estimated numbers of the three savanna-type African buffalo subspecies (S. c. caffer, S. c. brachyceros and S. c. aequinoctialis) are at 513,000 individuals. | African buffalo | Wikipedia | 496 | 564971 | https://en.wikipedia.org/wiki/African%20buffalo | Biology and health sciences | Artiodactyla | null |
In the past, numbers of African buffaloes suffered their most severe collapse during the great rinderpest epidemic of the 1890s, which, coupled with pleuro-pneumonia, caused mortalities as high as 95% among livestock and wild ungulates.
Being a member of the big five game group, a term used to describe the five most dangerous animals to hunt, the Cape buffalo is a sought-after trophy, with some hunters paying over $10,000 for the opportunity to hunt one. The larger bulls are targeted for their trophy value, although in some areas, buffaloes are still hunted for meat.
Attacks
One of the "big five" African game, it is known as "the Black Death" or "the widowmaker", and is widely regarded as a very dangerous animal. African buffaloes are sometimes reported to kill more people in Africa than any other animal, although the same claim is also made of hippopotamuses and crocodiles. These numbers may be somewhat overestimated; for example, in the country of Mozambique, attacks, especially fatal ones, were much less frequent on humans than those by hippos, and especially, Nile crocodiles. In Uganda, on the other hand, large herbivores were found to attack more people on average than lions or leopards and have a higher rate of inflicting fatalities during attacks than the predators (the African buffalo, in particular, killing humans in 49.5% of attacks on them), but hippos and even elephants may still kill more people per annum than buffaloes. African buffaloes are notorious among big-game hunters as very dangerous animals, with wounded animals reported to ambush and attack pursuers.
Domestication
The Cape buffalo hybridized with Indian water buffalo to create the Jafarabadi buffalo breed. | African buffalo | Wikipedia | 365 | 564971 | https://en.wikipedia.org/wiki/African%20buffalo | Biology and health sciences | Artiodactyla | null |
The mesopelagic zone (Greek μέσον, middle), also known as the middle pelagic or twilight zone, is the part of the pelagic zone that lies between the photic epipelagic and the aphotic bathypelagic zones. It is defined by light, and begins at the depth where only 1% of incident light reaches and ends where there is no light; the depths of this zone are between approximately 200 to 1,000 meters (~656 to 3,280 feet) below the ocean surface.
The mesopelagic zone occupies about 60% of the planet's surface and about 20% of the ocean's volume, amounting to a large part of the total biosphere. It hosts a diverse biological community that includes bristlemouths, blobfish, bioluminescent jellyfish, giant squid, and a myriad of other unique organisms adapted to live in a low-light environment. It has long captivated the imagination of scientists, artists and writers; deep sea creatures are prominent in popular culture.
Physical conditions
The mesopelagic zone includes the region of sharp changes in temperature, salinity and density called the thermocline, halocline, and pycnocline respectively. The temperature variations are large; from over 20 °C (68 °F) at the upper layers to around 4 °C (39 °F) at the boundary with the bathyal zone. The variation in salinity is smaller, typically between 34.5 and 35 psu. The density ranges from 1023 to 1027 g/L of seawater. These changes in temperature, salinity, and density induce stratification which create ocean layers. These different water masses affect gradients and mixing of nutrients and dissolved gasses. This makes this a dynamic zone. | Mesopelagic zone | Wikipedia | 377 | 565530 | https://en.wikipedia.org/wiki/Mesopelagic%20zone | Physical sciences | Oceanography | Earth science |
The mesopelagic zone has some unique acoustic features. The Sound Fixing and Ranging (SOFAR) channel, where sound travels the slowest due to salinity and temperature variations, is located at the base of the mesopelagic zone at about 600–1,200m. It is a wave-guided zone where sound waves refract within the layer and propagate long distances. The channel got its name during World War II when the US Navy proposed using it as a life saving tool. Shipwreck survivors could drop a small explosive timed to explode in the SOFAR channel and then listening stations could determine the position of the life raft. During the 1950s, the US Navy tried to use this zone to detect Soviet submarines by creating an array of hydrophones called the Sound Surveillance System (SOSUS.) Oceanographers later used this underwater surveillance system to figure out the speed and direction of deep ocean currents by dropping SOFAR floats that could be detected with the SOSUS array.
The mesopelagic zone is important for water mass formation, such as mode water. Mode water is a water mass that is typically defined by its vertically mixed properties. It often forms as deep mixed layers at the depth of the thermocline. The mode water in the mesopelagic has residency times on decadal or century scales. The longer overturning times contrast with the daily and shorter scales that a variety of animals move vertically through the zone and sinking of various debris.
Biogeochemistry
Carbon
The mesopelagic zone plays a key role in the ocean's biological pump, which contributes to the oceanic carbon cycle. In the biological pump, organic carbon is produced in the surface euphotic zone where light promotes photosynthesis. A fraction of this production is exported out of the surface mixed layer and into the mesopelagic zone. One pathway for carbon export from the euphotic layer is through sinking of particles, which can be accelerated through repackaging of organic matter in zooplankton fecal pellets, ballasted particles, and aggregates. | Mesopelagic zone | Wikipedia | 427 | 565530 | https://en.wikipedia.org/wiki/Mesopelagic%20zone | Physical sciences | Oceanography | Earth science |
In the mesopelagic zone, the biological pump is key to carbon cycling, as this zone is largely dominated by remineralization of particulate organic carbon (POC). When a fraction of POC is exported from the euphotic zone, an estimated 90% of that POC is respired in the mesopelagic zone. This is due to the microbial organisms that respire organic matter and remineralize the nutrients, while mesopelagic fish also package organic matter into quick-sinking parcels for deeper export.
Another key process occurring in this zone is the diel vertical migration of certain species, which move between the euphotic zone and mesopelagic zone and actively transport particulate organic matter to the deep. In one study in the Equatorial Pacific, myctophids in the mesopelagic zone were estimated to actively transport 15–28% of the passive POC sinking to the deep, while a study near the Canary Islands estimated 53% of vertical carbon flux was due to active transport from a combination of zooplankton and micronekton. When primary productivity is high, the contribution of active transport by vertical migration has been estimated to be comparable to sinking particle export.
Particle Packaging and sinking
Mean particle sinking rates are 10 to 100 m/day. Sinking rates have been measured in the project VERTIGO (Vertical Transport in the Global Ocean) using settling velocity sediment traps. The variability in sinking rates is due to differences in ballast, water temperature, food web structure and the types of phyto and zooplankton in different areas of the ocean. If the material sinks faster, then it gets respired less by bacteria, transporting more carbon from the surface layer to the deep ocean. Larger fecal pellets sink faster due to lower friction-surface/mass ratio. More viscous waters could slow the sinking rate of particles. | Mesopelagic zone | Wikipedia | 386 | 565530 | https://en.wikipedia.org/wiki/Mesopelagic%20zone | Physical sciences | Oceanography | Earth science |
Oxygen
Dissolved oxygen is a requirement for aerobic respiration, and while the surface ocean is usually oxygen-rich due to atmospheric gas exchange and photosynthesis, the mesopelagic zone is not in direct contact with the atmosphere, due to stratification at the base of the surface mixed layer. Organic matter is exported to the mesopelagic zone from the overlying euphotic layer, while the minimal light in the mesopelagic zone limits photosynthesis. The oxygen consumption due to respiration of most of the sinking organic matter and lack of gas exchange, often creates an oxygen minimum zone (OMZ) in the mesopelagic. The mesopelagic OMZ is particularly severe in the eastern tropical Pacific Ocean and tropical Indian Ocean due to poor ventilation and high rates of organic carbon export to the mesopelagic. Oxygen concentrations in the mesopelagic are occasionally result in suboxic concentrations, making aerobic respiration difficult for organisms. In these anoxic regions, chemosynthesis may occur in which CO2 and reduced compounds such as sulfide or ammonia are taken up to form organic carbon, contributing to the organic carbon reservoir in the mesopelagic. This pathway of carbon fixation has been estimated to be comparable in rate to the contribution by heterotrophic production in this ocean realm.
Nitrogen
The mesopelagic zone, an area of significant respiration and remineralization of organic particles, is generally nutrient-rich. This is in contrast to the overlying euphotic zone, which is often nutrient-limited. Areas of low oxygen such as OMZ's are a key area of denitrification by prokaryotes, a heterotrophic pathways in which nitrate is converted into nitrogen gas, resulting in a loss to the ocean reservoir of reactive nitrogen. At the suboxic interface that occurs at the edge of the OMZ, nitrite and ammonium can be coupled to produce nitrogen gas through anammox, also removing nitrogen from the biologically available pool.
Biology | Mesopelagic zone | Wikipedia | 419 | 565530 | https://en.wikipedia.org/wiki/Mesopelagic%20zone | Physical sciences | Oceanography | Earth science |
Although some light penetrates the mesopelagic zone, it is insufficient for photosynthesis. The biological community of the mesopelagic zone has adapted to a low-light environment. This is a very efficient ecosystem with many organisms recycling the organic matter sinking from the epipelagic zone resulting in very little organic carbon making it to deeper ocean waters. The general types of life forms found are daytime-visiting herbivores, detritivores feeding on dead organisms and fecal pellets, and carnivores feeding on those detritivores.
Many organisms in the mesopelagic zone move up into the epipelagic zone at night, and retreat to the mesopelagic zone during the day, which is known as diel vertical migration. These migrators can therefore avoid visual predators during the day and feed at night, while some of their predators also migrate up at night to follow the prey. There is so much biomass in this migration that sonar operators in World War II would regularly misinterpret the signal returned by this thick layer of plankton as a false sea floor.
Estimates of the global biomass of mesopelagic fishes range from 1 gigatonne (Gt) based on net tows to 7–10 Gt based on measurements using active acoustics.
Virus and microbial ecology
Very little is known about the microbial community of the mesopelagic zone because it is a difficult part of the ocean to study. Recent work using DNA from seawater samples emphasized the importance of viruses and microbes role in recycling organic matter from the surface ocean, known as the microbial loop. These many microbes can get their energy from different metabolic pathways. Some are autotrophs, heterotrophs, and a 2006 study even discovered chemoautotrophs. This chemoautotrophic Archaea crenarchaeon Candidatus can oxidize ammonium as their energy source without oxygen, which could significantly impact the nitrogen and carbon cycles. One study estimates these ammonium-oxidizing bacteria, which are only 5% of the microbial population, can annually capture 1.1 Gt of organic carbon. | Mesopelagic zone | Wikipedia | 444 | 565530 | https://en.wikipedia.org/wiki/Mesopelagic%20zone | Physical sciences | Oceanography | Earth science |
Microbial biomass and diversity typically decline exponentially with depth in the mesopelagic zone, tracking the general decline of food from above. The community composition varies with depths in the mesopelagic as different organisms are evolved for varying light conditions. Microbial biomass in the mesopelagic is greater at higher latitudes and decreases towards the tropics, which is likely linked to the differing productivity levels in the surface waters. Viruses however are very abundant in the mesopelagic, with around 1010 - 1012 every cubic meter, which is fairly uniform throughout the mesopelagic zone.
Zooplankton ecology
The mesopelagic zone hosts a diverse zooplankton community. Common zooplankton include copepods, krill, jellyfish, siphonophores, larvaceans, cephalopods, and pteropods. Food is generally scarce in the mesopelagic, so predators have to be efficient in capturing food. Gelatinous organisms are thought to play an important role in the ecology of the mesopelagic and are common predators. Though previously thought to be passive predators just drifting through the water column, jellyfish could be more active predators. One study found that the helmet jellyfish Periphylla periphylla exhibit social behavior and can find each other at depth and form groups. Such behavior was previously attributed to mating, but scientists speculate this could be a feeding strategy to allow a group of jellyfish to hunt together. Mesopelagic zooplankton have unique adaptations for the low light. Bioluminescence is a very common strategy in many zooplankton. This light production is thought to function as a form of communication between conspecifics, prey attraction, prey deterrence, and/or reproduction strategy. Another common adaption are enhanced light organs, or eyes, which is common in krill and shrimp, so they can take advantage of the limited light. Some octopus and krill even have tubular eyes that look upwards in the water column.
Most life processes, like growth rates and reproductive rates, are slower in the mesopelagic. Metabolic activity has been shown to decrease with increasing depth and decreasing temperature in colder-water environments. For example, the mesopelagic shrimp-like mysid, Gnathophausia ingens, lives for 6.4 to 8 years, while similar benthic shrimp only live for 2 years.
Fish ecology | Mesopelagic zone | Wikipedia | 506 | 565530 | https://en.wikipedia.org/wiki/Mesopelagic%20zone | Physical sciences | Oceanography | Earth science |
The mesopelagic is home to a significant portion of the world's total fish biomass. Mesopelagic fish are found globally, with exceptions in the Arctic Ocean. A 1980 study puts the mesopelagic fish biomass at about one billion tons. Then a 2008 study estimated the world marine fish biomass at between 0.8 and 2 billion tons. A more recent study concluded mesopelagic fish could have a biomass amounting to 10 billion tons, equivalent to about 100 times the annual catch of traditional fisheries of about 100 million metric tons. However, there is a lot of uncertainty in this biomass estimate. This ocean realm could contain the largest fishery in the world and there is active development for this zone to become a commercial fishery.
There are currently thirty families of known mesopelagic fish. One dominant fish in the mesopelagic zone are lanternfish (Myctophidae), which include 245 species distributed among 33 different genera. They have prominent photophores along their ventral side. The Gonostomatidae, or bristlemouth, are also common mesopelagic fish. The bristlemouth could be the Earth's most abundant vertebrate, with numbers in the hundreds of trillions to quadrillions.
Mesopelagic fish are difficult to study due to their unique anatomy. Many of these fish have swim bladders to help them control their buoyancy, which makes them hard to sample because those gas-filled chambers typically burst as the fish come up in nets and the fish die. Scientists in California have made progress on mesopelagic fish sampling by developing a submersible chamber that can keep fish alive on the way up to the surface under a controlled atmosphere and pressure. A passive method to estimate mesopelagic fish abundance is by echosounding to locate the 'deep scattering layer' through the backscatter received from these acoustic sounders. A 2015 study suggested that some areas have had a decline in abundance of mesopelagic fish, including off the coast of Southern California, using a long-term study dating back to the 1970s. Cold water species were especially vulnerable to decline. | Mesopelagic zone | Wikipedia | 438 | 565530 | https://en.wikipedia.org/wiki/Mesopelagic%20zone | Physical sciences | Oceanography | Earth science |
Mesopelagic fish are adapted to a low-light environment. Many fish are black or red, because these colors appear dark due to the limited light penetration at depth. Some fish have rows of photophores, small light-producing organs, on their underside to mimic the surrounding environment. Other fish have mirrored bodies which are angled to reflect the surrounding ocean low-light colors and protect the fish from being seen, while another adaptation is countershading where fish have light colors on the ventral side and dark colors on the dorsal side.
Food is often limited and patchy in the mesopelagic, leading to dietary adaptations. Common adaptations fish may have include sensitive eyes and huge jaws for enhanced and opportunistic feeding. Fish are also generally small to reduce the energy requirement for growth and muscle formation. Other feeding adaptations include jaws that can unhinge, elastic throats, and massive, long teeth. Some predators develop bioluminescent lures, like the tasselled anglerfish, which can attract prey, while others respond to pressure or chemical cues instead of relying on vision.
Human impacts
Pollution
Marine debris
Marine debris, specifically in the plastic form, have been found in every ocean basin and have a wide range of impacts on the marine world.
One of the most critical issues is ingestion of plastic debris, specifically microplastics. Many mesopelagic fish species migrate to the surface waters to feast on their main prey species, zooplankton and phytoplankton, which are mixed with microplastics in the surface waters. Additionally, research has shown that even zooplankton are consuming the microplastics themselves. Mesopelagic fish play a key role in energy dynamics, meaning they provide food to a number of predators including birds, larger fish and marine mammals. The concentration of these plastics has the potential to increase, so more economically important species could become contaminated as well. Concentration of plastic debris in mesopelagic populations can vary depending on geographic location and the concentration of marine debris located there. In 2018, approximately 73% of approximately 200 fish sampled in the North Atlantic had consumed plastic. | Mesopelagic zone | Wikipedia | 439 | 565530 | https://en.wikipedia.org/wiki/Mesopelagic%20zone | Physical sciences | Oceanography | Earth science |
Bioaccumulation
Bioaccumulation (a buildup of a certain substance in the adipose tissue) and biomagnification (the process in which the concentration of the substance grows higher as you rise through the food chain) are growing issues in the mesopelagic zone. Mercury in fish can be traced back to a combination of anthropological factors (such as coal mining) in addition to natural factors. Mercury is a particularly important bioaccumulation contaminant because its concentration in the mesopelagic zone is increasing faster than in surface waters. Inorganic mercury occurs in anthropogenic atmospheric emissions in its gaseous elemental form, which then oxidizes and can be deposited in the ocean. Once there, the oxidized form can be converted to methylmercury, which is its organic form. Research suggests that current levels anthropogenic emissions will not equilibrate between the atmosphere and ocean for a period of decades to centuries, which means we can expect current mercury concentrations in the ocean to keep rising. Mercury is a potent neurotoxin, and poses health risks to the whole food web, beyond the mesopelagic species that consume it. Many of the mesopelagic species, such as myctophids, that make their diel vertical migration to the surface waters, can transfer the neurotoxin when they are consumed by pelagic fish, birds and mammals.
Fishing
Historically, there have been few examples of efforts to commercialize the mesopelagic zone due to low economic value, technical feasibility and environmental impacts. While the biomass may be abundant, fish species at depth are generally smaller in size and slower to reproduce. Fishing with large trawl nets poses threats to a high percentage of bycatch as well as potential impacts to the carbon cycling processes. Additionally, ships trying to reach productive mesopelagic regions requires fairly long journeys offshore. In 1977, a Soviet fishery opened but closed less than 20 years later due to low commercial profits, while a South African purse seine fishery closed in the mid-1980s due to processing difficulties from the high oil content of fish. | Mesopelagic zone | Wikipedia | 434 | 565530 | https://en.wikipedia.org/wiki/Mesopelagic%20zone | Physical sciences | Oceanography | Earth science |
As the biomass in the mesopelagic is so abundant, there has been an increased interest to determine whether these populations could be of economic use in sectors other than direct human consumption. For example, it has been suggested that the high abundance of fish in this zone could potentially satisfy a demand for fishmeal and nutraceuticals. With a growing global population, the demand for fishmeal in support of a growing aquaculture industry is high. There is potential for an economically viable harvest. For example, 5 billion tons of mesopelagic biomass could result in the production of circa 1.25 billion tons of food for human consumption. Additionally, the demand for nutraceuticals is also rapidly growing, stemming from the popular human consumption of Omega-3 Fatty Acids in addition to the aquaculture industry that requires a specific marine oil for feed material. Lanternfish are of much interest to the aquaculture market, as they are especially high in fatty acids.
Climate Change
The mesopelagic region plays an important role in the global carbon cycle, as it is the area where most of the surface organic matter is respired. Mesopelagic species also acquire carbon during their diel vertical migration to feed in surface waters, and they transport that carbon to the deep sea when they die. It is estimated that the mesopelagic cycles between 5 and 12 billion tons of carbon dioxide from the atmosphere per year, and until recently, this estimate was not included in many climate models. It is difficult to quantify the effects of climate change on the mesopelagic zone as a whole, as climate change does not have uniform impacts geographically. Research suggests that in warming waters, as long as there are adequate nutrients and food for fish, then mesopelagic biomass could actually increase due to higher trophic efficiency and increased temperature-driven metabolism. However, because ocean warming will not be uniform throughout the global mesopelagic zone, it is predicted that some areas may actually decrease in fish biomass, while others increase. | Mesopelagic zone | Wikipedia | 411 | 565530 | https://en.wikipedia.org/wiki/Mesopelagic%20zone | Physical sciences | Oceanography | Earth science |
Water column stratification will also likely increase with ocean warming and climate change. Increased ocean stratification reduces the introduction of nutrients from the deep ocean into the euphotic zone resulting in decreases in both net primary production and sinking particulate matter. Additional research suggests shifts in the geographical range of many species could also occur with warming, with many of them shifting poleward. The combination of these factors could potentially mean that as global ocean basins continue to warm, there could be areas in the mesopelagic that increase in biodiversity and species richness, while declines in other areas, especially moving farther from the equator.
Research and Exploration
There is a dearth of knowledge about the mesopelagic zone so researchers have begun to develop new technology to explore and sample this area. The Woods Hole Oceanographic Institution (WHOI), NASA, and the Norwegian Institute of Marine Research are all working on projects to gain a better understanding of this zone in the ocean and its influence on the global carbon cycle. Traditional sampling methods like nets have proved to be inadequate because they scare off creatures due to the pressure wave formed by the towed net and the light produced by the bioluminescent species caught in the net.
Mesopelagic activity was first investigated by use of sonar because the return bounces off of plankton and fish in the water. However, there are many challenges with acoustic survey methods and previous research has estimated errors in measured amounts of biomass of up to three orders of magnitude. This is due to inaccurate incorporation of depth, species size distribution, and acoustic properties of the species. Norway's Institute of Marine Research has launched a research vessel named Dr. Fridtjof Nansen to investigate mesopelagic activity using sonar with their focus being on the sustainability of fishing operations. To overcome the challenges faced with acoustic sampling, WHOI is developing remote operated vehicles (ROVs) and robots (Deep-See, Mesobot, and Snowclops) that are capable of studying this zone more precisely in a dedicated effort called the Ocean Twilight Zone project that launched in August 2018. | Mesopelagic zone | Wikipedia | 420 | 565530 | https://en.wikipedia.org/wiki/Mesopelagic%20zone | Physical sciences | Oceanography | Earth science |
Discovery and Detection
The deep scattering layer often characterizes the mesopelagic due to the high amount of biomass that exists in the region. Acoustic sound sent into the ocean bounces off particles and organisms in the water column and return a strong signal. The region was initially discovered by American researchers during World War II in 1942 during anti-submarine research with sonar. Sonar at the time could not penetrate below this depth due to the large number of creatures obstructing sound waves. It is uncommon to detect deep scattering layers below 1000m. Until recently, sonar has been the predominant method for studying the mesopelagic.
The Malaspina Circumnavigation Expedition was a Spanish-led scientific quest in 2011 to gain a better understanding of the state of the ocean and the diversity in the deep oceans. The data collected, particularly through sonar observations showed that the biomass estimation in the mesopelagic was lower than previously thought.
Deep-See
WHOI is currently working on a project to characterize and document the pelagic ecosystem. They have developed a device named Deep-See weighing approximately 700 kg, which is designed to be towed behind a research vessel. The Deep-See is capable of reaching depths up to 2000 m and can estimate the amount of biomass and biodiversity in this mesopelagic ecosystem. Deep-See is equipped with cameras, sonars, sensors, water sample collection devices, and a real-time data transmission system.
Mesobot
WHOI is collaborating with the Monterey Bay Aquarium Research Institute (MBARI), Stanford University, and the University of Texas Rio Grande Valley to develop a small autonomous robot, Mesobot, weighing approximately 75 kg. Mesobot is equipped with high-definition cameras to track and record mesopelagic species on their daily migration over extended periods of time. The robot's thrusters were designed so that they do not disturb the life in the mesopelagic that it is observing. Traditional sample collection devices fail to preserve organisms captured in the mesopelagic due to the large pressure change associated with surfacing. The Mesobot also has a unique sampling mechanism that is capable of keeping the organisms alive during their ascent. The first sea trial of this device is expected to be in 2019. | Mesopelagic zone | Wikipedia | 457 | 565530 | https://en.wikipedia.org/wiki/Mesopelagic%20zone | Physical sciences | Oceanography | Earth science |
MINIONS
Another mesopelagic robot developed by WHOI are the MINIONS. This device descends down the water column and takes images of the amount and size distribution of marine snow at various depths. These tiny particles are a food source for other organisms so it is important to monitor the different levels of marine snow to characterize the carbon cycling processes between the surface ocean and the mesopelagic.
SPLAT cam
The Harbor Branch Oceanographic Institute has developed the Spatial PLankton Analysis Technique (SPLAT) to identify and map distribution patterns of bioluminescent plankton. The various bioluminescent species produce a unique flash that allows the SPLAT to distinguish each specie's flash characteristic and then map their 3-dimensional distribution patterns. Its intended use was not for investigating the mesopelagic zone, although it is capable of tracking movement patterns of bioluminescent species during their vertical migrations. It would be interesting to apply this mapping technique in the mesopelagic to obtain more information about the diurnal vertical migrations that occur in this zone of the ocean. | Mesopelagic zone | Wikipedia | 218 | 565530 | https://en.wikipedia.org/wiki/Mesopelagic%20zone | Physical sciences | Oceanography | Earth science |
The bathypelagic zone or bathyal zone (from Greek βαθύς (bathýs), deep) is the part of the open ocean that extends from a depth of below the ocean surface. It lies between the mesopelagic above and the abyssopelagic below. The bathypelagic is also known as the midnight zone because of the lack of sunlight; this feature does not allow for photosynthesis-driven primary production, preventing growth of phytoplankton or aquatic plants. Although larger by volume than the photic zone, human knowledge of the bathypelagic zone remains limited by ability to explore the deep ocean.
Physical characteristics
The bathypelagic zone is characterized by a nearly constant temperature of approximately and a salinity range of 33-35 g/kg. This region has little to no light because sunlight does not reach this deep in the ocean and bioluminescence is limited. The hydrostatic pressure in this zone ranges from 100-400 atmospheres (atm) due to the increase of 1 atm for every 10 m depth. It is believed that these conditions have been consistent for the past 8000 years.
This ocean depth spans from the edge of the continental shelf down to the top of the abyssal zone, and along continental slope depths. The bathymetry of the bathypelagic zone consists of limited areas where the seafloor is in this depth range along the deepest parts of the continental margins, as well as seamounts and mid-ocean ridges. The continental slopes are mostly made up of accumulated sediment, while seamounts and mid-ocean ridges contain large areas of hard substrate that provide habitats for bathypelagic fishes and benthic invertebrates. Although currents at these depths are very slow, the topography of seamounts interrupts the currents and creates eddies that retain plankton in the seamount region, thus increasing fauna nearby as well
Hydrothermal vents are also a common feature in some areas of the bathypelagic zone and are primarily formed from the spreading of Earth's tectonic plates at mid-ocean ridges. As the bathypelagic region lacks light, these vents play an important role in global ocean chemical processes, thus supporting unique ecosystems that have adapted to utilize chemicals as energy, via chemoautotrophy, instead of sunlight, to sustain themselves. In addition, hydrothermal vents facilitate precipitation of minerals on the seafloor, making them regions of interest for deep-sea mining.
Biogeochemistry | Bathypelagic zone | Wikipedia | 511 | 565536 | https://en.wikipedia.org/wiki/Bathypelagic%20zone | Physical sciences | Oceanography | Earth science |
Many of the biogeochemical processes in the bathypelagic region are dependent upon the input of organic matter from the overlying epipelagic and mesopelagic zones. This organic material, sometimes called marine snow, sinks in the water column or is transported within downward convected water masses such as the Thermohaline Circulation. Hydrothermal vents also deliver heat and chemicals such as sulfide and methane. These chemicals can be utilized to sustain metabolism by organisms in the region. Our understanding of these biogeochemical processes has historically been limited due to the difficulty and cost of collecting samples from these ocean depths. Other technological challenges, such as measuring microbial activity under the pressure conditions experienced in the bathypelagic zone, have also restricted our knowledge of the region. Although scientific advancements have increased our understanding over the past several decades, many aspects remain a mystery. One of the major areas of current research is focused on understanding carbon remineralization rates in the region. Prior studies have struggled to quantify the rates at which prokaryotes in this region remineralize carbon because previously developed techniques may not be adequate for this region, and indicate remineralization rates much higher than expected. Further work is needed to explore this question, and may require revisions to our understanding of the global carbon cycle.
Particulate organic matter
Organic material from primary production in the epipelagic zone, and to a far lesser extent, organic inputs from terrestrial sources, make up a majority of the Particulate Organic Matter (POM) in the ocean. POM is delivered to the bathypelagic zone via sinking copepod fecal pellets and dead organisms; these parcels of organic matter fall through the water column and deliver organic carbon, nitrogen, and phosphorus, to organisms that live below the photic zone. These parcels are sometimes referred to as marine snow or ocean dandruff. This is also the dominant delivery mechanism of food to organisms in the bathypelagic zone because there is no sunlight for photosynthesis, with chemoautotrophy playing a more minor role as far as we know. | Bathypelagic zone | Wikipedia | 437 | 565536 | https://en.wikipedia.org/wiki/Bathypelagic%20zone | Physical sciences | Oceanography | Earth science |
As POM sinks through the water column, it is consumed by organisms which deplete it of nutrients. The size and density of these particles affect their likelihood of reaching organisms in the bathypelagic zone. Smaller parcels of POM often become aggregated together as they fall, which quickens their descent and prohibits their consumption by other organisms, increasing their likelihood of reaching lower depths. The density of these particles may be increased in some regions where minerals associated with some forms of phytoplankton, such as biogenic silica and calcium carbonate "ballast" resulting in more rapid transport to deeper depth.
Carbon
A majority of organic carbon is produced in the epipelagic zone, with a small portion transported deeper into the ocean interior. This process, known as the biological pump, plays a large role in the sequestration of carbon from the atmosphere into the ocean. Organic carbon is primarily exported to the bathypelagic zone in the form of particulate organic carbon (POC) and dissolved organic carbon (DOC).
POC is the largest component of organic carbon delivered to the bathypelagic zone; it primarily takes the form of fecal pellets and dead organisms that sink out of the surface waters and fall toward the ocean floor. Regions with higher primary productivity where particles are able to sink quickly, such as equatorial upwelling zones and the Arabian Sea, have the greatest amount of POC delivery to the bathypelagic zone.
The vertical mixing of DOC-rich surface waters is also a process that delivers carbon to the bathypelagic zone, however, it constitutes a substantially smaller portion of overall transport than POC delivery. DOC transport occurs most readily in regions with high rates of ventilation or ocean turnover, such as the interior of gyres or deep water formation sites along the thermohaline circulation. | Bathypelagic zone | Wikipedia | 375 | 565536 | https://en.wikipedia.org/wiki/Bathypelagic%20zone | Physical sciences | Oceanography | Earth science |
Calcium carbonate dissolution
The region in the water column at which calcite dissolution begins to occur rapidly, known as the lysocline, is typically located near the base bathypelagic zone at approximately 3,500 m depth, but varies among ocean basins. The lysocline lies below the saturation depth (the transition to undersaturated conditions with respect to calcium carbonate) and above the carbonate compensation depth (below which there is no calcium carbonate preservation). In a supersaturated environment, the tests of calcite-forming organisms are preserved as they sink toward the sea floor, resulting in sediments with relatively high amounts of CaCO3. However, as depth and pressure increase and temperature decreases, the solubility of calcium carbonate also increases, which results in more dissolution and less net transport to the deeper, underlying seafloor. As a result of this rapid change in dissolution rates, sediments in the bathypelagic region vary widely in CaCO3 content and burial.
Ecology
The ecology of the bathypelagic ecosystem is constrained by its lack of sunlight and primary producers, with limited production of microbial biomass via autotrophy. The trophic networks in this region rely on particulate organic matter (POM) that sinks from the epipelagic and mesopelagic water, and oxygen inputs from the thermohaline circulation. Despite these limitations, this open-ocean ecosystem is home to microbial organisms, fish, and nekton.
Microbial ecology
A comprehensive understanding of the inputs driving the microbial ecology in the bathypelagic zone is lacking due to limited observational data, but has been improving with advancements in deep-sea technology. A majority of our knowledge of ocean microbial activity comes from studies of the shallower regions of the ocean because it is easier to access, and it was previously assumed that deeper water did not have suitable physical conditions for diverse microbial communities. The bathypelagic zone receives inputs of organic material and POM from the surface ocean on the order of 1-3.6 Pg C/year. | Bathypelagic zone | Wikipedia | 425 | 565536 | https://en.wikipedia.org/wiki/Bathypelagic%20zone | Physical sciences | Oceanography | Earth science |
Prokaryote biomass in the bathypelagic is dependent and thus correlated with the amount of sinking POM and organic carbon availability. These essential organic carbon inputs for microbes typically decrease with depth as they are utilized while sinking to the bathypelagic. Microbial production varies over six orders of magnitude based on resource availability in a given area. Prokaryote abundance can range from 0.03-2.3x105 cells ml−1, and have population turnover times that can range from 0.1–30 years. Archaea make up a larger portion of the total prokaryote cell abundance, and different groups have different growth needs, with some archaea groups for example utilizing amino acid groups more readily than others. Some archaea like Crenarchaeota have Crenarchaeota 16S rRNA and archaeal amoA gene abundances correlated to dissolved inorganic carbon (DIC) fixation. The utilization of DIC is thought to be fueled by the oxidation of ammonium and is one form of chemoautotrophy. Based on regional variation and differences in prokaryote abundance, heterotrophic prokaryote production, and particulate organic carbon (POC) inputs to the bathypelagic zone.
Research to quantify bacterial-consuming grazers, like heterotrophic eukaryotes, has been limited by difficulties in sampling. Oftentimes organisms do not survive being brought to the surface due to experiencing drastic pressure changes in a short amount of time. Work is underway to quantify cell abundance and biomass, but due to poor survival, it is difficult to get accurate counts. In more recent years there has been an effort to categorize the diversity of the eukaryotic assemblages in the bathypelagic zone using methods to assess the genetic compositions of microbial communities based on supergroups, which is a way to classify organisms that have common ancestry. Some important groups of bacterial grazers include Rhizaria, Alveolata, Fungi, Stramenopiles, Amoebozoa, and Excavata (listed from most to least abundant), with the remaining composition classified as uncertain or other. | Bathypelagic zone | Wikipedia | 454 | 565536 | https://en.wikipedia.org/wiki/Bathypelagic%20zone | Physical sciences | Oceanography | Earth science |
Viruses influence biogeochemical cycling through the role they play in marine food webs. Their overall abundance can be up to two orders of magnitude lower than the mesopelagic zone, however, there is often high viral abundance found around deep-sea hydrothermal vents. The magnitude of their impacts on biological systems is demonstrated by the varying range of viral-to-prokaryote abundance ratios ranging from 1-223, this indicates that there are the same amount or more viruses than prokaryotes.
Fauna
Fish ecology
Despite the lack of light, vision plays a role in life within the bathypelagic with bioluminescence a trait among both nektonic and planktonic organisms. In contrast to organisms in the water column, benthic organisms in this region tend to have limited to no bioluminescence. The bathypelagic zone contains sharks, squid, octopuses, and many species of fish, including deep-water anglerfish, gulper eel, amphipods, and dragonfish. The fish are characterized by weak muscles, soft skin, and slimy bodies. The adaptations of some of the fish that live there include small eyes and transparent skin. However, this zone is difficult for fish to live in since food is scarce; resulting in species evolving slow metabolic rates in order to conserve energy. Occasionally, large sources of organic matter from decaying organisms, such as whale falls, create a brief burst of activity by attracting organisms from different bathypelagic communities. | Bathypelagic zone | Wikipedia | 304 | 565536 | https://en.wikipedia.org/wiki/Bathypelagic%20zone | Physical sciences | Oceanography | Earth science |
Diel vertical migration
Some bathypelagic species undergo vertical migration, which differs from the diel vertical migration of mesopelagic species in that it is not driven by sunlight. Instead, the migration of bathypelagic organisms is driven by other factors, most of which remain unknown. Some research suggests the movement of species within the overlying pelagic region could prompt individual bathypelagic species to migrate, such as Sthenoteuthis sp., a species of squid. In this particular example, Sthenoteuthis sp. appears to migrate individually over the course of ~4–5 hours towards the surface and then form into groups. While in most regions migration patterns can be driven by predation, in this particular region, the migration patterns are not believed to result solely from predator-prey relations. Instead, these relations are commensalistic, with the species who remain in the bathypelagic benefitting from the POM mixing caused by the upward movement of another species. In addition, the vertical migrating species' timing bathypelagic appears linked to the lunar cycle. However, the exact indicators causing this timing are still unknown.
Research and exploration
This region is understudied due to a lack of data/observations and difficulty of access (i.e. cost, remote locations, extreme pressure). Historically in oceanography, continental margins were the most sampled and researched due to their relatively easy access. However, more recently locations further offshore and at greater depths, such as ocean ridges and seamounts, are being increasingly studied due to advances in technology and laboratory methods, as well as collaboration with industry. The first discovery of communities subsisting off of the chemical energy in hydrothermal vents was aboard an expedition in 1977 led by Jack Corliss, an oceanographer from Oregon State University. More recent advancements include remotely operated vehicles (ROVs), autonomous underwater vehicles (AUVs), and independent gliders and floats.
Specific technologies and research projects
SERPENT Project
Ocean Twilight Zone (OTZ) Project
DEEP SEARCH Project
DEEPEND Project
AUV Sentry
ROV Jason
Hybrid ROV Nereus
AUV Autosub Long Range
Climate change | Bathypelagic zone | Wikipedia | 441 | 565536 | https://en.wikipedia.org/wiki/Bathypelagic%20zone | Physical sciences | Oceanography | Earth science |
The oceans act as a buffer for anthropogenic climate change due to their ability to take up atmospheric CO2 and absorb heat from the atmosphere. However, the ocean's ability to do so will be negatively affected as atmospheric CO2 concentrations continue to rise and global temperatures continue to warm. This will lead to changes such as deoxygenation, ocean acidification, temperature increase, and carbon sequestration decrease, among other physical and chemical alterations. These perturbations may have significant impacts on the organisms that dwell in the bathypelagic region and the properties that deliver organic carbon to the deep sea.
Carbon storage
The bathypelagic zone currently acts as a significant reservoir for carbon because of its sheer volume and the century to millennial timescales these waters are isolated from the atmosphere, this ocean zone plays an important role in moderating the effects of anthropogenic climate change. The burial of particulate organic carbon (POC) in the underlying sediments via the biological carbon pump, and the solubility pump of dissolved inorganic carbon (DIC) into the ocean interior via the thermohaline conveyor are key processes for removing excess atmospheric carbon. However, as atmospheric CO2 concentrations and global temperatures continue to rise, the efficiency at which the bathypelagic will store and bury the influx of carbon will most likely decrease. While some regions may experience an increase in POC input, such as Arctic regions where increased periods of minimal sea ice coverage will increase the downward flux of carbon from the surface oceans, overall, there will likely be less carbon sequestered to the bathypelagic region. | Bathypelagic zone | Wikipedia | 332 | 565536 | https://en.wikipedia.org/wiki/Bathypelagic%20zone | Physical sciences | Oceanography | Earth science |
Centaurea cyanus, commonly known as cornflower or bachelor's button, is an annual flowering plant in the family Asteraceae native to Europe. In the past, it often grew as a weed in cornfields (in the broad sense of "corn", referring to grains, such as wheat, barley, rye, or oats), hence its name. It is now endangered in its native habitat by agricultural intensification, particularly by over-use of herbicides. However, Centaurea cyanus is now also naturalised in many other parts of the world, including North America and parts of Australia through introduction as an ornamental plant in gardens and as a seed contaminant in crop seeds.
Description
Centaurea cyanus is an annual plant growing to tall, with grey-green branched stems. The leaves are lanceolate and long. The flowers are most commonly an intense blue colour and arranged in flowerheads (capitula) of 1.5–3 cm diameter, with a ring of a few large, spreading ray florets surrounding a central cluster of disc florets. The blue pigment is protocyanin, which in roses is red. Fruits are approx. 3.5 mm long with 2–3 mm-long pappus bristles. It flowers all summer.
Genetics
Centaurea cyanus is a diploid flower (2n = 24). The genetic diversity within populations is high, although there could be a future decline in diversity due to population fragmentation and intensive agriculture. In general, Centaurea cyanus is a self-incompatible species. However, selfing still occurs occasionally, but results in inbreeding depression.
Distribution and habitat
Centaurea cyanus is native to temperate Europe, but is widely naturalized outside its native range.
It has been present in Britain and Ireland as an archaeophyte (ancient introduction) since the Iron Age. In the United Kingdom, it has declined from 264 sites to just 3 sites in the last 50 years.
In reaction to this, the conservation charity Plantlife named it as one of 101 species it would actively work to bring 'back from the brink'.
In the County Clare (VC H9) in Ireland, C. cyanus is recorded in arable fields as very rare and almost extinct, while in northeast Ireland, it was abundant before the 1930s.
Ecology | Centaurea cyanus | Wikipedia | 482 | 566041 | https://en.wikipedia.org/wiki/Centaurea%20cyanus | Biology and health sciences | Asterales | Plants |
Weed in arable crops
Centaurea cyanus is considered a noxious weed in arable crops, especially cereals and rapeseed. In winter wheat, one plant per m2 can cause a yield loss of up to 30 kg / ha. Centaurea cyanus produces around 800 seed per plant, which are either shed shortly before the harvest of cereals, or they are threshed together with the cereal grains, contributing to the further spread of the species by the harvesting machinery and contaminated seed. The occurrence of Centaurea cyanus strongly decreased during the last decades due to improved seed cleaning, more intensive nitrogen fertilization and herbicide use. However, Centaurea cyanus has become more common in cropland due to an increase in crop rotations dominated by winter cereals and rapeseed and the use of more selective herbicides with a low effectiveness against Centaurea cyanus. In addition, the emergence of resistance against the herbicide class of sulfonylureas has been reported recently. Due to its strong roots, Centaurea cyanus is difficult to control mechanically in spring.
Fodder for insects and birds
The pollen of Centaurea cyanus is used by several different insect species. Insects of the orders Hymenoptera and Diptera are particularly attracted by the flower. As Centaurea cyanus is a self-incompatible species, it needs external pollination. The nectar of Centaurea cyanus is very sweet with a sugar content of 34%. Due to its high sugar production of up to 0.2 mg sugar per day and flower, the species is highly appreciated by beekeepers.
The seeds of Centaurea cyanus are one of the favourite foods of the European goldfinch. | Centaurea cyanus | Wikipedia | 355 | 566041 | https://en.wikipedia.org/wiki/Centaurea%20cyanus | Biology and health sciences | Asterales | Plants |
Control of insect pests
Centaurea cyanus was found to produce volatiles attracting Microplitis mediator, which is a major parasitoid of the cabbage moth (Mamestra brassicae), which is the most important pest of cabbage (Brassica oleracea) in central Europe. Planting Centaurea cyanus in cabbage fields as a companion plant was thus suggested as an alternative to the widespread use of insecticides to control Mamestra brassicae. Field experiments showed that planting Centaurea cyanus in cabbage fields at a density of 1 plant / m2 can result in a significant increase in parasitation of Mamestra brassicae larvae, predation of Mamestra brassicae eggs (e.g. by carabid beetles or spiders) and ultimately cabbage yield.
Cultivation
Several cultivars of Centaurea cyanus with varying pastel colours, including pink and purple, have been selected for ornamental purposes. The species is also grown for the cut flower industry in Canada for use by florists. Doubled blue cultivars (such as 'Blue Boy' or 'Blue Diadem') are most commonly used for this purpose, but white, pink, lavender and black (actually a very dark maroon) cultivars are also used, albeit to a lesser extent. There are varieties with blue, white, purple, pink or even black petals.
Breeding goals
As for all ornamental plants, important goals of Centaurea cyanus breeding include the induction of phenotypic variation (e.g. in flower coloration, size and shape, foliage characteristics or plant height), higher flower yield, resistance to pests and diseases as well as tolerance to abiotic stress (e.g., extreme temperatures, drought or salinity).
Soil and climate requirements
Centaurea cyanus requires full sun and neutral (pH 6.6–7.5) to mildly alkaline (pH 7.6–7.8), moist and well-drained soil. However, Centaurea cyanus is quite tolerant to drought once established. | Centaurea cyanus | Wikipedia | 426 | 566041 | https://en.wikipedia.org/wiki/Centaurea%20cyanus | Biology and health sciences | Asterales | Plants |
Sowing
For summer-blooming plants, sowing should be executed in late spring. In moderate climates, however, it is also possible to sow Centaurea cyanus in early fall. In this case, plants will already start to flower in the following spring. Recommended spacing between plants is approx. 20 to 30 cm. Centaurea cyanus can germinate from up to 10 cm depth, but the best result is obtained at 1 cm sowing depth. Germination occurs quickly after sowing.
Fertilization and cultural practices
High phosphorus fertilization in mid-summer will increase flower production. Mulching is recommended to prevent drying out of the soil and exposure of the root system to the sun.
Pests and diseases
In general, Centaurea cyanus is not very susceptible to pests and plant diseases. However, it may be affected by stem rot and stem rust if grown too tightly or by powdery mildew. Furthermore, aphids and leafhoppers can cause relevant damage to Centaurea cyanus.
Seed harvesting
Seeds are harvested either by hand or, in an agricultural setting, with a seed harvesting machine. On average there are 97,000 seeds in a pound of cornflower seeds.
Hand collecting can be time-consuming and yields are rather low.
A seed harvesting machine is more efficient than collecting the seeds by hand, but it is costly. The main principle of such a machine is that it brushes the ripe seeds off the plant and creates a cross flow fan action that generates sufficient air velocity to hold and gather the seeds into the seed bunker.
Pruning
Deadheading will encourage the plant to produce more blooms. Cornflowers are often used for ornamental purposes and by cutting them, up to their third leaves, they will produce more blooms and grow a bigger stem.
Uses
Culinary
The flowers of Centaurea cyanus can be eaten raw, dried or cooked. Dried petals are used in foods, including in spices. Their main purpose is to add colour to food. There are cheeses or oils that contain raw petals. Petals can also be added to salads, drinks, and desserts for garnishing purposes in raw or dried form.
Dried petals are also used in teas and other beverages. Blue cornflower petals are sometimes one of the ingredients in Lady Grey tea. | Centaurea cyanus | Wikipedia | 472 | 566041 | https://en.wikipedia.org/wiki/Centaurea%20cyanus | Biology and health sciences | Asterales | Plants |
Medicine
Centaurea cyanus contains a wide range of pharmacologically active compounds, such as flavonoids, anthocyanins and aromatic acids. Especially the flower head finds application in herbal medicine, but leaves and seeds are also used for pharmacological purposes, albeit to a lesser extent.
In particular, extracts from the flower heads have anti-inflammatory properties used in the treatment of minor ocular inflammations. Antioxidant properties are high due to ascorbic acid and phenolic compounds. Furthermore, extracts of the flower head and vegetative parts of the plant were shown to have gastroprotective effects due to their content of quercetin, apigenin and caffeic acid derivates.
Pigment
The blue color of Centaurea cyanus is due to protocyanin, an anthocyanin pigment that is also found in roses. Different anthocyanins derived from Centaurea cyanus are used as natural additives in food products, such as yoghurts.
Phytoremediation
Centaurea cyanus has been evaluated for phytoremediation of soils contaminated with lead. Inoculation of the contaminated soil with Glomus spp. (fungus) and Pseudomonas spp. (bacterium) would significantly enhance the biomass production and lead uptake of Centaurea cyanus.
In culture
In folklore, cornflowers were worn by young men in love; if the flower faded too quickly, it was taken as a sign that the man's love was not returned.
The blue cornflower was one of the national symbols of Germany. This is partly due to the story that when Queen Louise of Prussia was fleeing Berlin and pursued by Napoleon's forces, she hid her children in a field of cornflowers and kept them quiet by weaving wreaths for them from the flowers. The flower thus became identified with Prussia, not least because it was the same color as the Prussian military uniform. After the unification of Germany in 1871, it went on to become a symbol of the country as a whole. For this reason, in Austria the blue cornflower is a political symbol for pan-German and rightist ideas. It was worn as a secret symbol identifying members of the then-illegal NSDAP in Austria in the 1930s. Members of the Freedom Party wore it at the openings of the Austrian parliament since 2006. After the last general election 2017 they replaced it with the edelweiss. | Centaurea cyanus | Wikipedia | 507 | 566041 | https://en.wikipedia.org/wiki/Centaurea%20cyanus | Biology and health sciences | Asterales | Plants |
It was also the favourite flower of Louise's son Kaiser Wilhelm I. Because of its ties to royalty, authors such as Theodor Fontane have used it symbolically, often sarcastically, to comment on the social and political climate of the time.
The cornflower is also often seen as an inspiration for the German Romantic symbol of the Blue Flower.
Due to its traditional association with Germany, the cornflower has been made the official symbol of the annual German-American Steuben Parade.
The blue cornflower has been the national flower of Estonia since 1969 and symbolizes daily bread to Estonians. It is also the symbol of the Estonian Conservative People's Party.
It is also the symbol of the Finnish National Coalition Party, and the Liberal People's Party of Sweden, where it has since the dawn of the 20th century been a symbol for social liberalism.
It is the official flower of the Swedish province of Östergötland and the school flower of Winchester College and also of Dulwich College, where it is said to have been the favourite flower of the founder, Edward Alleyn.
In France the is the symbol of the 11 November 1918 armistice and, as such, a common symbol for veterans (especially the now defunct poilus of World War I), similar to the Remembrance poppies worn in the United Kingdom and in Canada.
The cornflower is also the symbol for motor neurone disease and amyotrophic lateral sclerosis.
Cornflowers are sometimes worn by Old Harrovians, former pupils of the British Harrow School.
A blue cornflower was used by Corning Glass Works for the initial release of Corning Ware Pyroceram cookware. Its popularity in the United States, Canada, United Kingdom and Australia was so high that it became the symbol of Corning Glass Works.
In paintings | Centaurea cyanus | Wikipedia | 370 | 566041 | https://en.wikipedia.org/wiki/Centaurea%20cyanus | Biology and health sciences | Asterales | Plants |
In solid-state physics, a metal–semiconductor (M–S) junction is a type of electrical junction in which a metal comes in close contact with a semiconductor material. It is the oldest type of practical semiconductor device. M–S junctions can either be rectifying or non-rectifying. The rectifying metal–semiconductor junction forms a Schottky barrier, making a device known as a Schottky diode, while the non-rectifying junction is called an ohmic contact. (In contrast, a rectifying semiconductor–semiconductor junction, the most common semiconductor device today, is known as a p–n junction.)
Metal–semiconductor junctions are crucial to the operation of all semiconductor devices. Usually an ohmic contact is desired, so that electrical charge can be conducted easily between the active region of a transistor and the external circuitry.
Occasionally however a Schottky barrier is useful, as in Schottky diodes, Schottky transistors, and metal–semiconductor field effect transistors.
The critical parameter: Schottky barrier height
Whether a given metal-semiconductor junction is an ohmic contact or a Schottky barrier depends on the Schottky barrier height, ΦB, of the junction.
For a sufficiently large Schottky barrier height, that is, ΦB is significantly higher than the thermal energy kT, the semiconductor is depleted near the metal and behaves as a Schottky barrier. For lower Schottky barrier heights, the semiconductor is not depleted and instead forms an ohmic contact to the metal.
The Schottky barrier height is defined differently for n-type and p-type semiconductors (being measured from the conduction band edge and valence band edge, respectively). The alignment of the semiconductor's bands near the junction is typically independent of the semiconductor's doping level, so the n-type and p-type Schottky barrier heights are ideally related to each other by:
where Eg is the semiconductor's band gap.
In practice, the Schottky barrier height is not precisely constant across the interface, and varies over the interfacial surface.
Schottky–Mott rule and Fermi level pinning | Metal–semiconductor junction | Wikipedia | 468 | 14355756 | https://en.wikipedia.org/wiki/Metal%E2%80%93semiconductor%20junction | Physical sciences | Electrical circuits | Physics |
The Schottky–Mott rule of Schottky barrier formation, named for Walter H. Schottky and Nevill Mott, predicts the Schottky barrier height based on the vacuum work function of the metal relative to the vacuum electron affinity (or vacuum ionization energy) of the semiconductor:
This model is derived based on the thought experiment of bringing together the two materials in vacuum, and is closely related in logic to Anderson's rule for semiconductor-semiconductor junctions. Different semiconductors respect the Schottky–Mott rule to varying degrees.
Although the Schottky–Mott model correctly predicted the existence of band bending in the semiconductor, it was found experimentally that it would give grossly incorrect predictions for the height of the Schottky barrier. A phenomenon referred to as "Fermi level pinning" caused some point of the band gap, at which finite DOS exists, to be locked (pinned) to the Fermi level. This made the Schottky barrier height almost completely insensitive to the metal's work function:
where Ebandgap is the size of band gap in the semiconductor.
In fact, empirically, it is found that neither of the above extremes is quite correct. The choice of metal does have some effect, and there appears to be a weak correlation between the metal work function and the barrier height, however the influence of the work function is only a fraction of that predicted by the Schottky-Mott rule.
It was noted in 1947 by John Bardeen that the Fermi level pinning phenomenon would naturally arise if there were chargeable states in the semiconductor right at the interface, with energies inside the semiconductor's gap. These would either be induced during the direct chemical bonding of the metal and semiconductor (metal-induced gap states) or be already present in the semiconductor–vacuum surface (surface states). These highly dense surface states would be able to absorb a large quantity of charge donated from the metal, effectively shielding the semiconductor from the details of the metal. As a result, the semiconductor's bands would necessarily align to a location relative to the surface states which are in turn pinned to the Fermi level (due to their high density), all without influence from the metal. | Metal–semiconductor junction | Wikipedia | 464 | 14355756 | https://en.wikipedia.org/wiki/Metal%E2%80%93semiconductor%20junction | Physical sciences | Electrical circuits | Physics |
The Fermi level pinning effect is strong in many commercially important semiconductors (Si, Ge, GaAs), and thus can be problematic for the design of semiconductor devices. For example, nearly all metals form a significant Schottky barrier to n-type germanium and an ohmic contact to p-type germanium, since the valence band edge is strongly pinned to the metal's Fermi level. The solution to this inflexibility requires additional processing steps such as adding an intermediate insulating layer to unpin the bands. (In the case of germanium, germanium nitride has been used)
History
The rectification property of metal–semiconductor contacts was discovered by Ferdinand Braun in 1874 using mercury metal contacted with copper sulfide and iron sulfide semiconductors. Sir Jagadish Chandra Bose applied for a US patent for a metal-semiconductor diode in 1901. This patent was awarded in 1904. G.W. Pickard received a patent in 1906 on a point-contact rectifier using silicon. In 1907, George W. Pierce published a paper in Physical Review showing rectification properties of diodes made by sputtering many metals on many semiconductors. The use of the metal–semiconductor diode rectifier was proposed by Lilienfeld in 1926 in the first of his three transistor patents as the gate of the metal–semiconductor field effect transistors. The theory of the field-effect transistor using a metal/semiconductor gate was advanced by William Shockley in 1939. | Metal–semiconductor junction | Wikipedia | 316 | 14355756 | https://en.wikipedia.org/wiki/Metal%E2%80%93semiconductor%20junction | Physical sciences | Electrical circuits | Physics |
The earliest metal–semiconductor diodes in electronics application occurred around 1900, when the cat's whisker rectifiers were used in receivers. They consisted of pointed tungsten wire (in the shape of a cat's whisker) whose tip or point was pressed against the surface of a galena (lead sulfide) crystal. The first large area rectifier appeared around 1926 which consisted of a copper(I) oxide semiconductor thermally grown on a copper substrate. Subsequently, selenium films were evaporated onto large metal substrates to form the rectifying diodes. These selenium rectifiers were used (and are still used) to convert alternating current to direct current in electrical power applications. During 1925–1940, diodes consisting of a pointed tungsten metal wire in contact with a silicon crystal base, were fabricated in laboratories to detect microwaves in the UHF range. A World War II program to manufacture high-purity silicon as the crystal base for the point-contact rectifier was suggested by Frederick Seitz in 1942 and successfully undertaken by the Experimental Station of the E. I du Pont de Nemours Company. | Metal–semiconductor junction | Wikipedia | 239 | 14355756 | https://en.wikipedia.org/wiki/Metal%E2%80%93semiconductor%20junction | Physical sciences | Electrical circuits | Physics |
The first theory that predicted the correct direction of rectification of the metal–semiconductor junction was given by Nevill Mott in 1939. He found the solution for both the diffusion and drift currents of the majority carriers through the semiconductor surface space charge layer which has been known since about 1948 as the Mott barrier. Walter H. Schottky and Spenke extended Mott's theory by including a donor ion whose density is spatially constant through the semiconductor surface layer. This changed the constant electric field assumed by Mott to a linearly decaying electric field. This semiconductor space-charge layer under the metal is known as the Schottky barrier. A similar theory was also proposed by Davydov in 1939. Although it gives the correct direction of rectification, it has also been proven that the Mott theory and its Schottky-Davydov extension gives the wrong current limiting mechanism and wrong current-voltage formulae in silicon metal/semiconductor diode rectifiers. The correct theory was developed by Hans Bethe and reported by him in a M.I.T. Radiation Laboratory Report dated November 23, 1942. In Bethe's theory, the current is limited by thermionic emission of electrons over the metal–semiconductor potential barrier. Thus, the appropriate name for the metal–semiconductor diode should be the Bethe diode, instead of the Schottky diode, since the Schottky theory does not predict the modern metal–semiconductor diode characteristics correctly.
If a metal-semiconductor junction is formed by placing a droplet of mercury, as Braun did, onto a semiconductor, e.g. silicon, to form a Schottky barrier in a Schottky diode electrical setup – electrowetting can be observed, where the droplet spreads out with increasing voltage. Depending on the doping type and density in the semiconductor, the droplet spreading depends on the magnitude and sign of the voltage applied to the mercury droplet. This effect has been termed ‘Schottky electrowetting’, effectively linking electrowetting and semiconductor effects.
Between 1953-1958, Fuller and Ditzenberger's work on the diffusion of impurities into silicon. In 1956 Miller and Savage studied the diffusion of aluminium in crystal silicon. | Metal–semiconductor junction | Wikipedia | 468 | 14355756 | https://en.wikipedia.org/wiki/Metal%E2%80%93semiconductor%20junction | Physical sciences | Electrical circuits | Physics |
The first silicon oxide gate transistor were invented by Frosch and Derick in 1957 at Bell Labs. In 1956, Richard Baker described some discrete diode clamp circuits to keep transistors from saturating. The circuits are now known as Baker clamps. One of those clamp circuits used a single germanium diode to clamp a silicon transistor in a circuit configuration that is the same as the Schottky transistor. The circuit relied on the germanium diode having a lower forward voltage drop than a silicon diode would have.
The Schottky diode, also known as the Schottky-barrier diode, was theorized for years, but was first practically realized as a result of the work of Atalla and Kahng during 19601961. They published their results in 1962 and called their device the "hot electron" triode structure with semiconductor-metal emitter. It was one of the first metal-base transistors. Atalla continued research on Schottky diodes with Robert J. Archer at HP Associates. They developed high vacuum metal film deposition technology, and fabricated stable evaporated/sputtered contacts, publishing their results in January 1963. Their work was a breakthrough in metal–semiconductor junction and Schottky barrier research, as it overcame most of the fabrication problems inherent in point-contact diodes and made it possible to build practical Schottky diodes.
In 1967, Robert Kerwin, Donald Klein and John Sarace at Bell Labs, patented a method to replaced the aluminum gate with a polycrystalline layer of silicon. | Metal–semiconductor junction | Wikipedia | 336 | 14355756 | https://en.wikipedia.org/wiki/Metal%E2%80%93semiconductor%20junction | Physical sciences | Electrical circuits | Physics |
The smart grid is an enhancement of the 20th century electrical grid, using two-way communications and distributed so-called intelligent devices. Two-way flows of electricity and information could improve the delivery network. Research is mainly focused on three systems of a smart grid – the infrastructure system, the management system, and the protection system. Electronic power conditioning and control of the production and distribution of electricity are important aspects of the smart grid.
The smart grid represents the full suite of current and proposed responses to the challenges of electricity supply. Numerous contributions to the overall improvement of energy infrastructure efficiency are anticipated from the deployment of smart grid technology, in particular including demand-side management. The improved flexibility of the smart grid permits greater penetration of highly variable renewable energy sources such as solar power and wind power, even without the addition of energy storage. Smart grids could also monitor/control residential devices that are noncritical during periods of peak power consumption, and return their function during nonpeak hours.
A smart grid includes a variety of operation and energy measures:
Advanced metering infrastructure (of which smart meters are a generic name for any utility side device even if it is more capable e.g. a fiber optic router)
Smart distribution boards and circuit breakers integrated with home control and demand response (behind the meter from a utility perspective)
Load control switches and smart appliances, often financed by efficiency gains on municipal programs (e.g. PACE financing)
Renewable energy resources, including the capacity to charge parked (electric vehicle) batteries or larger arrays of batteries recycled from these, or other energy storage.
Energy efficient resources
Electric surplus distribution by power lines and auto-smart switch
Sufficient utility grade fiber broadband to connect and monitor the above, with wireless as a backup. Sufficient spare if "dark" capacity to ensure failover, often leased for revenue.
Concerns with smart grid technology mostly focus on smart meters, items enabled by them, and general security issues. Roll-out of smart grid technology also implies a fundamental re-engineering of the electricity services industry, although typical usage of the term is focused on the technical infrastructure.
Smart grid policy is organized in Europe as Smart Grid European Technology Platform. Policy in the United States is described in Title 42 of the United States Code.
Background
Historical development of the electricity grid
The first alternating current power grid system was installed in 1886 in Great Barrington, Massachusetts. At that time, the grid was a centralized unidirectional system of electric power transmission, electricity distribution, and demand-driven control. | Smart grid | Wikipedia | 502 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
In the 20th century, local grids grew over time and were eventually interconnected for economic and reliability reasons. By the 1960s, the electric grids of developed countries had become very large, mature, and highly interconnected, with thousands of 'central' generation power stations delivering power to major load centres via high capacity power lines which were then branched and divided to provide power to smaller industrial and domestic users over the entire supply area. The topology of the 1960s grid was a result of the strong economies of scale: large coal-, gas- and oil-fired power stations in the 1 GW (1000 MW) to 3 GW scale are still found to be cost-effective, due to efficiency-boosting features that can be cost-effective only when the stations become very large.
Power stations were located strategically to be close to fossil fuel reserves (either the mines or wells themselves or else close to rail, road, or port supply lines). Siting of hydroelectric dams in mountain areas also strongly influenced the structure of the emerging grid. Nuclear power plants were sited for the availability of cooling water. Finally, fossil fuel-fired power stations were initially very polluting and were sited as far as economically possible from population centres once electricity distribution networks permitted it. By the late 1960s, the electricity grid reached the overwhelming majority of the population of developed countries, with only outlying regional areas remaining 'off-grid'.
Metering of electricity consumption was necessary on a per-user basis in order to allow appropriate billing according to the (highly variable) level of consumption of different users. Because of limited data collection and processing capability during the period of growth of the grid, fixed-tariff arrangements were commonly put in place, as well as dual-tariff arrangements where night-time power was charged at a lower rate than daytime power. The motivation for dual-tariff arrangements was the lower night-time demand. Dual tariffs made possible the use of low-cost night-time electrical power in applications such as the maintaining of 'heat banks' which served to 'smooth out' the daily demand, and reduce the number of turbines that needed to be turned off overnight, thereby improving the utilisation and profitability of the generation and transmission facilities. The metering capabilities of the 1960s grid meant technological limitations on the degree to which price signals could be propagated through the system. | Smart grid | Wikipedia | 474 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
From the 1970s to the 1990s, growing demand led to increasing numbers of power stations. In some areas, the supply of electricity, especially at peak times, could not keep up with this demand, resulting in poor power quality including blackouts, power cuts, and brownouts. Increasingly, electricity was depended on for industry, heating, communication, lighting, and entertainment, and consumers demanded ever-higher levels of reliability.
Towards the end of the 20th century, electricity demand patterns were established: domestic heating and air-conditioning led to daily peaks in demand that were met by an array of 'peaking power generators' that would only be turned on for short periods each day. The relatively low utilisation of these peaking generators (commonly, gas turbines were used due to their relatively lower capital cost and faster start-up times), together with the necessary redundancy in the electricity grid, resulting in high costs to the electricity companies, which were passed on in the form of increased tariffs.
In the 21st century, some developing countries like China, India, and Brazil were seen as pioneers of smart grid deployment.
Modernization opportunities
Since the early 21st century, opportunities to take advantage of improvements in electronic communication technology to resolve the limitations and costs of the electrical grid have become apparent. Technological limitations on metering no longer force peak power prices to be averaged out and passed on to all consumers equally. In parallel, growing concerns over environmental damage from fossil-fired power stations have led to a desire to use large amounts of renewable energy. Dominant forms such as wind power and solar power are highly variable, and so the need for more sophisticated control systems became apparent, to facilitate the connection of sources to the otherwise highly controllable grid. Power from photovoltaic cells (and to lesser extent wind turbines) has also, significantly, called into question the imperative for large, centralised power stations. The rapidly falling costs point to a major change from the centralised grid topology to one that is highly distributed, with power being both generated and consumed right at the limits of the grid. Finally, growing concern over terrorist attacks in some countries has led to calls for a more robust energy grid that is less dependent on centralised power stations that were perceived to be potential attack targets.
Definition of "smart grid" | Smart grid | Wikipedia | 457 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
United States
The first official definition of Smart Grid was provided by the Energy Independence and Security Act of 2007 (EISA-2007), which was approved by the US Congress in January 2007, and signed to law by President George W. Bush in December 2007. Title XIII of this bill provides a description, with ten characteristics, that can be considered a definition for Smart Grid, as follows:"It is the policy of the United States to support the modernization of the Nation's electricity transmission and distribution system to maintain a reliable and secure electricity infrastructure that can meet future demand growth and to achieve each of the following, which together characterize a Smart Grid: (1) Increased use of digital information and controls technology to improve reliability, security, and efficiency of the electric grid. (2) Dynamic optimization of grid operations and resources, with full cyber-security. (3) Deployment and integration of distributed resources and generation, including renewable resources. (4) Development and incorporation of demand response, demand-side resources, and energy-efficiency resources. (5) Deployment of 'smart' technologies (real-time, automated, interactive technologies that optimize the physical operation of appliances and consumer devices) for metering, communications concerning grid operations and status, and distribution automation. (6) Integration of 'smart' appliances and consumer devices. (7) Deployment and integration of advanced electricity storage and peak-shaving technologies, including plug-in electric and hybrid electric vehicles, and thermal storage air conditioning. (8) Provision to consumers of timely information and control options. (9) Development of standards for communication and interoperability of appliances and equipment connected to the electric grid, including the infrastructure serving the grid. (10) Identification and lowering of unreasonable or unnecessary barriers to adoption of smart grid technologies, practices, and services."
European Union
The European Union Commission Task Force for Smart Grids also provides smart grid definition as:
"A Smart Grid is an electricity network that can cost efficiently integrate the behaviour and actions of all users connected to it – generators, consumers and those that do both – in order to ensure economically efficient, sustainable power system with low losses and high levels of quality and security of supply and safety. A smart grid employs innovative products and services together with intelligent monitoring, control, communication, and self-healing technologies in order to: | Smart grid | Wikipedia | 470 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
Better facilitate the connection and operation of generators of all sizes and technologies.
Allow consumers to play a part in optimising the operation of the system.
Provide consumers with greater information and options for how they use their supply.
Significantly reduce the environmental impact of the whole electricity supply system.
Maintain or even improve the existing high levels of system reliability, quality and security of supply.
Maintain and improve the existing services efficiently."
That definition was used in the European Commission Communication (2011) 202.
A common element to most definitions is the application of digital processing and communications to the power grid, making data flow and information management central to the smart grid. Various capabilities result from the deeply integrated use of digital technology with power grids. Integration of the new grid information is one of the key issues in the design of smart grids. Electric utilities now find themselves making three classes of transformations: improvement of infrastructure, called the strong grid in China; addition of the digital layer, which is the essence of the smart grid; and business process transformation, necessary to capitalize on the investments in smart technology. Much of the work that has been going on in electric grid modernization, especially substation and distribution automation, is now included in the general concept of the smart grid.
Early technological innovations
Smart grid technologies emerged from earlier attempts at using electronic control, metering, and monitoring. In the 1980s, automatic meter reading was used for monitoring loads from large customers and evolved into the Advanced Metering Infrastructure of the 1990s, whose meters could store how electricity was used at different times of the day. Smart meters add continuous communications so that monitoring can be done in real-time, and can be used as a gateway to demand response-aware devices and "smart sockets" in the home. Early forms of such demand side management technologies were dynamic demand aware devices that passively sensed the load on the grid by monitoring changes in the power supply frequency. Devices such as industrial and domestic air conditioners, refrigerators, and heaters adjusted their duty cycle to avoid activation during times the grid was suffering a peak condition. Beginning in 2000, Italy's Telegestore Project was the first to network large numbers (27 million) of homes using smart meters connected via low bandwidth power line communication. Some experiments used the term broadband over power lines (BPL), while others used wireless technologies such as mesh networking promoted for more reliable connections to disparate devices in the home as well as supporting metering of other utilities such as gas and water. | Smart grid | Wikipedia | 502 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
Monitoring and synchronization of wide-area networks were revolutionized in the early 1990s when the Bonneville Power Administration expanded its smart grid research with prototype sensors that are capable of very rapid analysis of anomalies in electricity quality over very large geographic areas. The culmination of this work was the first operational Wide Area Measurement System (WAMS) in 2000. Other countries are rapidly integrating this technology — China started having a comprehensive national WAMS when the past 5-year economic plan was completed in 2012.
The earliest deployments of smart grids include the Italian system Telegestore (2005), the mesh network of Austin, Texas (since 2003), and the smart grid in Boulder, Colorado (2008). See below.
Features
A smart grid would allow the power industry to observe and control parts of the system at higher resolution in time and space. One of the purposes of the smart grid is real time information exchange to make operation as efficient as possible. It would allow management of the grid on all time scales from high-frequency switching devices on a microsecond scale, to wind and solar output variations on a minute scale, to the future effects of the carbon emissions generated by power production on a decade scale.
The smart grid represents the full suite of current and proposed responses to the challenges of electricity supply. Because of the diverse range of factors, there are numerous competing taxonomies and no agreement on a universal definition. Nevertheless, one possible categorization is given here.
Reliability
The smart grid makes use of technologies such as state estimation, that improve fault detection and allow self-healing of the network without the intervention of technicians. This will ensure a more reliable supply of electricity and reduce vulnerability to natural disasters or attacks.
Although multiple routes are touted as a feature of the smart grid, the old grid also featured multiple routes. Initial power lines in the grid were built using a radial model, later connectivity was guaranteed via multiple routes, referred to as a network structure. However, this created a new problem: if the current flow or related effects across the network exceed the limits of any particular network element, it could fail, and the current would be shunted to other network elements, which eventually may fail also, causing a domino effect. See power outage. A technique to prevent this is load shedding by rolling blackout or voltage reduction (brownout). | Smart grid | Wikipedia | 480 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
Flexibility in network topology
Next-generation transmission and distribution infrastructure will be better able to handle possible bidirectional energy flows, allowing for distributed generation such as from photovoltaic panels on building roofs, but also charging to/from the batteries of electric cars, wind turbines, pumped hydroelectric power, the use of fuel cells, and other sources.
Classic grids were designed for a one-way flow of electricity, but if a local sub-network generates more power than it is consuming, the reverse flow can raise safety and reliability issues. A smart grid aims to manage these situations.
Efficiency
Numerous contributions to the overall improvement of the efficiency of energy infrastructure are anticipated from the deployment of smart grid technology, in particular including demand-side management, for example turning off air conditioners during short-term spikes in electricity price, reducing the voltage when possible on distribution lines through Voltage/VAR Optimization (VVO), eliminating truck-rolls for meter reading, and reducing truck-rolls by improved outage management using data from Advanced Metering Infrastructure systems. The overall effect is less redundancy in transmission and distribution lines, and greater utilization of generators, leading to lower power prices.
Load adjustment/Load balancing
The total load connected to the power grid can vary significantly over time. Although the total load is the sum of many individual choices of the clients, the overall load is not necessarily stable or slow varying. For example, if a popular television program starts, millions of televisions will start to draw current instantly. Traditionally, to respond to a rapid increase in power consumption, faster than the start-up time of a large generator, some spare generators are put on a dissipative standby mode. A smart grid may warn all individual television sets, or another larger customer, to reduce the load temporarily (to allow time to start up a larger generator) or continuously (in the case of limited resources). Using mathematical prediction algorithms it is possible to predict how many standby generators need to be used, to reach a certain failure rate. In the traditional grid, the failure rate can only be reduced at the cost of more standby generators. In a smart grid, the load reduction by even a small portion of the clients may eliminate the problem.
Peak curtailment/leveling and time of use pricing | Smart grid | Wikipedia | 463 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
To reduce demand during the high-cost peak usage periods, communications and metering technologies inform smart devices in the home and business when energy demand is high and track how much electricity is used and when it is used. It also gives utility companies the ability to reduce consumption by communicating to devices directly in order to prevent system overloads. Examples would be a utility reducing the usage of a group of electric vehicle charging stations or shifting temperature set points of air conditioners in a city. To motivate them to cut back use and perform what is called peak curtailment or peak leveling, prices of electricity are increased during high demand periods and decreased during low demand periods. It is thought that consumers and businesses will tend to consume less during high-demand periods if it is possible for consumers and consumer devices to be aware of the high price premium for using electricity at peak periods. This could mean making trade-offs such as cycling on/off air conditioners or running dishwashers at 9 pm instead of 5 pm. When businesses and consumers see a direct economic benefit of using energy at off-peak times, the theory is that they will include the energy cost of operation into their consumer device and building construction decisions and hence become more energy efficient.
Sustainability
The improved flexibility of the smart grid permits greater penetration of highly variable renewable energy sources such as solar power and wind power, even without the addition of energy storage. Current network infrastructure is not built to allow for many distributed feed-in points, and typically even if some feed-in is allowed at the local (distribution) level, the transmission-level infrastructure cannot accommodate it. Rapid fluctuations in distributed generation, such as due to cloudy or gusty weather, present significant challenges to power engineers who need to ensure stable power levels through varying the output of the more controllable generators such as gas turbines and hydroelectric generators. Smart grid technology is a necessary condition for very large amounts of renewable electricity on the grid for this reason. There is also support for vehicle-to-grid. | Smart grid | Wikipedia | 406 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
Market-enabling
The smart grid allows for systematic communication between suppliers (their energy price) and consumers (their willingness-to-pay), and permits both the suppliers and the consumers to be more flexible and sophisticated in their operational strategies. Only the critical loads will need to pay the peak energy prices, and consumers will be able to be more strategic in when they use energy. Generators with greater flexibility will be able to sell energy strategically for maximum profit, whereas inflexible generators such as base-load steam turbines and wind turbines will receive a varying tariff based on the level of demand and the status of the other generators currently operating. The overall effect is a signal that awards energy efficiency, and energy consumption that is sensitive to the time-varying limitations of the supply. At the domestic level, appliances with a degree of energy storage or thermal mass (such as refrigerators, heat banks, and heat pumps) will be well placed to 'play' the market and seek to minimise energy cost by adapting demand to the lower-cost energy support periods. This is an extension of the dual-tariff energy pricing mentioned above.
Demand response support
Demand response support allows generators and loads to interact in an automated fashion in real-time, coordinating demand to flatten spikes. Eliminating the fraction of demand that occurs in these spikes eliminates the cost of adding reserve generators, cuts wear and tear and extends the life of equipment, and allows users to cut their energy bills by telling low priority devices to use energy only when it is cheapest.
Currently, power grid systems have varying degrees of communication within control systems for their high-value assets, such as in generating plants, transmission lines, substations, and major energy users. In general, information flows one way, from the users and the loads they control back to the utilities. The utilities attempt to meet the demand and succeed or fail to varying degrees (brownouts, rolling blackout, uncontrolled blackout). The total amount of power demanded by the users can have a very wide probability distribution which requires spare generating plants in standby mode to respond to the rapidly changing power usage. This one-way flow of information is expensive; the last 10% of generating capacity may be required as little as 1% of the time, and brownouts and outages can be costly to consumers. | Smart grid | Wikipedia | 468 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
Demand response can be provided by commercial, residential loads, and industrial loads. For example, Alcoa's Warrick Operation is participating in MISO as a qualified Demand Response Resource, and the Trimet Aluminium uses its smelter as a short-term mega-battery.
Latency of the data flow is a major concern, with some early smart meter architectures allowing actually as long as 24 hours delay in receiving the data, preventing any possible reaction by either supplying or demanding devices.
Technology | Smart grid | Wikipedia | 100 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
The bulk of smart grid technologies are already used in other applications such as manufacturing and telecommunications and are being adapted for use in grid operations.
Integrated communications: Areas for improvement include: substation automation, demand response, distribution automation, supervisory control, and data acquisition (SCADA), energy management systems, wireless mesh networks and other technologies, power-line carrier communications, and fiber-optics. Integrated communications will allow for real-time control, information, and data exchange to optimize system reliability, asset utilization, and security.
Sensing and measurement: core duties are evaluating congestion and grid stability, monitoring equipment health, energy theft prevention, and control strategies support. Technologies include advanced microprocessor meters (smart meter) and meter reading equipment, wide-area monitoring systems, (typically based on online readings by Distributed temperature sensing combined with Real time thermal rating (RTTR) systems), electromagnetic signature measurement/analysis, time-of-use, and real-time pricing tools, advanced switches and cables, backscatter radio technology, and Digital protective relays.
Smart meters.
Phasor measurement units. Many in the power systems engineering community believe that the Northeast blackout of 2003 could have been contained to a much smaller area if a wide area phasor measurement network had been in place.
Distributed power flow control: power flow control devices clamp onto existing transmission lines to control the flow of power within. Transmission lines enabled with such devices support greater use of renewable energy by providing more consistent, real-time control over how that energy is routed within the grid. This technology enables the grid to more effectively store intermittent energy from renewables for later use. | Smart grid | Wikipedia | 332 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
Smart power generation using advanced components: smart power generation is a concept of matching electricity generation with demand using multiple identical generators which can start, stop and operate efficiently at chosen load, independently of the others, making them suitable for baseload and peaking power generation. Matching supply and demand, called load balancing, is essential for a stable and reliable supply of electricity. Short-term deviations in the balance lead to frequency variations and a prolonged mismatch results in blackouts. Operators of power transmission systems a charged with the balancing task, matching the power output of all the generators to the load of their electrical grid. The load balancing task has become much more challenging as increasingly intermittent and variable generators such as wind turbines and solar cells are added to the grid, forcing other producers to adapt their output much more frequently than has been required in the past. The first two dynamic grid stability power plants utilizing the concept have been ordered by Elering and will be built by Wärtsilä in Kiisa, Estonia (Kiisa Power Plant). Their purpose is to "provide dynamic generation capacity to meet sudden and unexpected drops in the electricity supply". They are scheduled to be ready during 2013 and 2014, and their total output will be 250 MW.
Power system automation enables rapid diagnosis of and precise solutions to specific grid disruptions or outages. These technologies rely on and contribute to each of the other four key areas. Three technology categories for advanced control methods are distributed intelligent agents (control systems), analytical tools (software algorithms and high-speed computers), and operational applications (SCADA, substation automation, demand response, etc.). Using artificial intelligence programming techniques, the Fujian power grid in China created a wide area protection system that is rapidly able to accurately calculate a control strategy and execute it. The Voltage Stability Monitoring & Control (VSMC) software uses a sensitivity-based successive linear programming method to reliably determine the optimal control solution. | Smart grid | Wikipedia | 389 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
Research
Major programs
IntelliGrid – Created by the Electric Power Research Institute (EPRI), IntelliGrid architecture provides methodology, tools, and recommendations for standards and technologies for utility use in planning, specifying, and procuring IT-based systems, such as advanced metering, distribution automation, and demand response. The architecture also provides a living laboratory for assessing devices, systems, and technology. Several utilities have applied IntelliGrid architecture including Southern California Edison, Long Island Power Authority, Salt River Project, and TXU Electric Delivery. The IntelliGrid Consortium is a public/private partnership that integrates and optimizes global research efforts, funds technology R&D, works to integrate technologies, and disseminates technical information.
Grid 2030 – Grid 2030 is a joint vision statement for the U.S. electrical system developed by the electric utility industry, equipment manufacturers, information technology providers, federal and state government agencies, interest groups, universities, and national laboratories. It covers generation, transmission, distribution, storage, and end-use. The National Electric Delivery Technologies Roadmap is the implementation document for the Grid 2030 vision. The Roadmap outlines the key issues and challenges for modernizing the grid and suggests paths that government and industry can take to build America's future electric delivery system.
Modern Grid Initiative (MGI) is a collaborative effort between the U.S. Department of Energy (DOE), the National Energy Technology Laboratory (NETL), utilities, consumers, researchers, and other grid stakeholders to modernize and integrate the U.S. electrical grid. DOE's Office of Electricity Delivery and Energy Reliability (OE) sponsors the initiative, which builds upon Grid 2030 and the National Electricity Delivery Technologies Roadmap and is aligned with other programs such as GridWise and GridWorks.
GridWise – A DOE OE program focused on developing information technology to modernize the U.S. electrical grid. Working with the GridWise Alliance, the program invests in communications architecture and standards; simulation and analysis tools; smart technologies; test beds and demonstration projects; and new regulatory, institutional, and market frameworks. The GridWise Alliance is a consortium of public and private electricity sector stakeholders, providing a forum for idea exchanges, cooperative efforts, and meetings with policy makers at federal and state levels. | Smart grid | Wikipedia | 477 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
GridWise Architecture Council (GWAC) was formed by the U.S. Department of Energy to promote and enable interoperability among the many entities that interact with the nation's electric power system. The GWAC members are a balanced and respected team representing the many constituencies of the electricity supply chain and users. The GWAC provides industry guidance and tools to articulate the goal of interoperability across the electric system, identify the concepts and architectures needed to make interoperability possible, and develop actionable steps to facilitate the inter operation of the systems, devices, and institutions that encompass the nation's electric system. The GridWise Architecture Council Interoperability Context Setting Framework, V 1.1 defines necessary guidelines and principles.
GridWorks – A DOE OE program focused on improving the reliability of the electric system through modernizing key grid components such as cables and conductors, substations and protective systems, and power electronics. The program's focus includes coordinating efforts on high temperature superconducting systems, transmission reliability technologies, electric distribution technologies, energy storage devices, and GridWise systems.
Pacific Northwest Smart Grid Demonstration Project. - This project is a demonstration across five Pacific Northwest states-Idaho, Montana, Oregon, Washington, and Wyoming. It involves about 60,000 metered customers, and contains many key functions of the future smart grid.
Solar Cities - In Australia, the Solar Cities programme included close collaboration with energy companies to trial smart meters, peak and off-peak pricing, remote switching and related efforts. It also provided some limited funding for grid upgrades. | Smart grid | Wikipedia | 320 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
Smart Grid Energy Research Center (SMERC) - Located at University of California, Los Angeles dedicated its efforts to large-scale testing of its smart EV charging network technology. It created another platform for bidirectional flow of information between a utility and consumer end-devices. SMERC also developed a demand response (DR) test bed that comprises a Control Center, Demand Response Automation Server (DRAS), Home-Area-Network (HAN), Battery Energy Storage System (BESS), and photovoltaic (PV) panels. These technologies are installed within the Los Angeles Department of Water and Power and Southern California Edison territory as a network of EV chargers, battery energy storage systems, solar panels, DC fast charger, and Vehicle-to-Grid (V2G) units. These platforms, communications and control networks enables UCLA-led projects within the area to be tested in partnership with two local utilities, SCE and LADWP.
Smart Quart - In Germany, the Smart Quart project develops three smart districts to develop, test and showcase technology to operate smart grids. The project is a collaboration of E.ON, Viessmann, gridX and hydrogenious together with the RWTH Aachen University. It is planned that by the end of 2024 all three districts are supplied with locally generated energy and are largely independent of fossil energy sources.
Smart5Grid – In Portugal, aims to ensure that operators in the energy sector take advantage of the benefits associated with the use of 5G networks. With reliability and security, a solution is proposed to precisely address the specific requirements imposed by Smart Grids, such as high data transfer rates and real-time monitoring.
Smart grid modelling
Many different concepts have been used to model intelligent power grids. They are generally studied within the framework of complex systems. In a recent brainstorming session, the power grid was considered within the context of optimal control, ecology, human cognition, glassy dynamics, information theory, microphysics of clouds, and many others. Here is a selection of the types of analyses that have appeared in recent years.
Protection systems that verify and supervise themselves
Pelqim Spahiu and Ian R. Evans in their study introduced the concept of a substation based smart protection and hybrid Inspection Unit. | Smart grid | Wikipedia | 465 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
Kuramoto oscillators
The Kuramoto model is a well-studied system. The power grid has been described in this context as well. The goal is to keep the system in balance, or to maintain phase synchronization (also known as phase locking). Non-uniform oscillators also help to model different technologies, different types of power generators, patterns of consumption, and so on. The model has also been used to describe the synchronization patterns in the blinking of fireflies.
Smart Grid Communication Network
Network Simulators are used to simulate/emulate network communication effects. This typically involves setting up a lab with the smart grid devices, applications etc. with the virtual network being provided by the network simulator.
Neural networks
Neural networks have been considered for power grid management as well. Electric power systems can be classified in multiple different ways: non-linear, dynamic, discrete, or random. Artificial Neural Networks (ANNs) attempt to solve the most difficult of these problems, the non-linear problems.
Demand Forecasting
One application of ANNs is in demand forecasting. In order for grids to operate economically and reliably, demand forecasting is essential, because it is used to predict the amount of power that will be consumed by the load. This is dependent on weather conditions, type of day, random events, incidents, etc. For non-linear loads though, the load profile isn't smooth and as predictable, resulting in higher uncertainty and less accuracy using the traditional Artificial Intelligence models. Some factors that ANNs consider when developing these sort of models: classification of load profiles of different customer classes based on the consumption of electricity, increased responsiveness of demand to predict real time electricity prices as compared to conventional grids, the need to input past demand as different components, such as peak load, base load, valley load, average load, etc. instead of joining them into a single input, and lastly, the dependence of the type on specific input variables. An example of the last case would be given the type of day, whether its weekday or weekend, that wouldn't have much of an effect on Hospital grids, but it'd be a big factor in resident housing grids' load profile. | Smart grid | Wikipedia | 456 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
Markov processes
As wind power continues to gain popularity, it becomes a necessary ingredient in realistic power grid studies. Off-line storage, wind variability, supply, demand, pricing, and other factors can be modelled as a mathematical game. Here the goal is to develop a winning strategy. Markov processes have been used to model and study this type of system.
Economics
Market outlook
In 2009, the US smart grid industry was valued at about $21.4 billion – by 2014, it will exceed at least $42.8 billion. Given the success of the smart grids in the U.S., the world market is expected to grow at a faster rate, surging from $69.3 billion in 2009 to $171.4 billion by 2014. With the segments set to benefit the most will be smart metering hardware sellers and makers of software used to transmit and organize the massive amount of data collected by meters.
A 2011 study from the Electric Power Research Institute concludes that investment in a U.S. smart grid will cost up to $476 billion over 20 years but will provide up to $2 trillion in customer benefits over that time. In 2015, the World Economic Forum reported a transformational investment of more than $7.6 trillion by members of the OECD is needed over the next 25 years (or $300 billion per year) to modernize, expand, and decentralize the electricity infrastructure with technical innovation as key to the transformation. A 2019 study from International Energy Agency estimates that the current (depreciated) value of the US electric grid is more than USD 1 trillion. The total cost of replacing it with a smart grid is estimated to be more than USD 4 trillion. If smart grids are deployed fully across the US, the country expects to save USD 130 billion annually.
General economics developments
As customers can choose their electricity suppliers, depending on their different tariff methods, the focus of transportation costs will be increased. Reduction of maintenance and replacements costs will stimulate more advanced control.
A smart grid precisely limits electrical power down to the residential level, network small-scale distributed energy generation and storage devices, communicate information on operating status and needs, collect information on prices and grid conditions, and move the grid beyond central control to a collaborative network.
US and UK savings estimates and concerns | Smart grid | Wikipedia | 465 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
A 2003 United States Department of Energy study calculated that internal modernization of US grids with smart grid capabilities would save between 46 and 117 billion dollars over the next 20 years if implemented within a few years of the study. As well as these industrial modernization benefits, smart grid features could expand energy efficiency beyond the grid into the home by coordinating low priority home devices such as water heaters so that their use of power takes advantage of the most desirable energy sources. Smart grids can also coordinate the production of power from large numbers of small power producers such as owners of rooftop solar panels — an arrangement that would otherwise prove problematic for power systems operators at local utilities.
One important question is whether consumers will act in response to market signals. The U.S. Department of Energy (DOE) as part of the American Recovery and Reinvestment Act Smart Grid Investment Grant and Demonstrations Program funded special consumer behavior studies to examine the acceptance, retention, and response of consumers subscribed to time-based utility rate programs that involve advanced metering infrastructure and customer systems such as in-home displays and programmable communicating thermostats.
Another concern is that the cost of telecommunications to fully support smart grids may be prohibitive. A less expensive communication mechanism is proposed using a form of "dynamic demand management" where devices shave peaks by shifting their loads in reaction to grid frequency. Grid frequency could be used to communicate load information without the need of an additional telecommunication network, but it would not support economic bargaining or quantification of contributions.
Although there are specific and proven smart grid technologies in use, smart grid is an aggregate term for a set of related technologies on which a specification is generally agreed, rather than a name for a specific technology. Some of the benefits of such a modernized electricity network include the ability to reduce power consumption at the consumer side during peak hours, called demand side management; enabling grid connection of distributed generation power (with photovoltaic arrays, small wind turbines, micro hydro, or even combined heat power generators in buildings); incorporating grid energy storage for distributed generation load balancing; and eliminating or containing failures such as widespread power grid cascading failures. The increased efficiency and reliability of the smart grid is expected to save consumers money and help reduce emissions.
Oppositions and concerns | Smart grid | Wikipedia | 456 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
Most opposition and concerns have centered on smart meters and the items (such as remote control, remote disconnect, and variable rate pricing) enabled by them. Where opposition to smart meters is encountered, they are often marketed as "smart grid" which connects smart grid to smart meters in the eyes of opponents. Specific points of opposition or concern include:
consumer concerns over privacy, e.g. use of usage data by law enforcement
social concerns over "fair" availability of electricity
concern that complex rate systems (e.g. variable rates) remove clarity and accountability, allowing the supplier to take advantage of the customer
concern over remotely controllable "kill switch" incorporated into most smart meters
social concerns over Enron style abuses of information leverage
concerns over giving the government mechanisms to control the use of all power using activities
concerns over RF emissions from smart meters
Security
While modernization of electrical grids into smart grids allows for optimization of everyday processes, a smart grid, being online, can be vulnerable to cyberattacks. Transformers which increase the voltage of electricity created at power plants for long-distance travel, transmission lines themselves, and distribution lines which deliver the electricity to its consumers are particularly susceptible. These systems rely on sensors which gather information from the field and then deliver it to control centers, where algorithms automate analysis and decision-making processes. These decisions are sent back to the field, where existing equipment execute them. Hackers have the potential to disrupt these automated control systems, severing the channels which allow generated electricity to be utilized. This is called a denial of service or DoS attack. They can also launch integrity attacks which corrupt information being transmitted along the system as well as desynchronization attacks which affect when such information is delivered to the appropriate location. Additionally, intruders can gain access via renewable energy generation systems and smart meters connected to the grid, taking advantage of more specialized weaknesses or ones whose security has not been prioritized. Because a smart grid has a large number of access points, like smart meters, defending all of its weak points can prove difficult. | Smart grid | Wikipedia | 417 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
There is also concern on the security of the infrastructure, primarily that involving communications technology. Concerns chiefly center around the communications technology at the heart of the smart grid. Designed to allow real-time contact between utilities and meters in customers' homes and businesses, there is a risk that these capabilities could be exploited for criminal or even terrorist actions. One of the key capabilities of this connectivity is the ability to remotely switch off power supplies, enabling utilities to quickly and easily cease or modify supplies to customers who default on payment. This is undoubtedly a massive boon for energy providers, but also raises some significant security issues. Cybercriminals have infiltrated the U.S. electric grid before on numerous occasions. Aside from computer infiltration, there are also concerns that computer malware like Stuxnet, which targeted SCADA systems which are widely used in industry, could be used to attack a smart grid network.
Electricity theft is a concern in the U.S. where the smart meters being deployed use RF technology to communicate with the electricity transmission network. People with knowledge of electronics can devise interference devices to cause the smart meter to report lower than actual usage. Similarly, the same technology can be employed to make it appear that the energy the consumer is using is being used by another customer, increasing their bill.
The damage from a well-executed, sizable cyberattack could be extensive and long-lasting. One incapacitated substation could take from nine days to over a year to repair, depending on the nature of the attack. It can also cause an hours-long outage in a small radius. It could have an immediate effect on transportation infrastructure, as traffic lights and other routing mechanisms as well as ventilation equipment for underground roadways is reliant on electricity. Additionally, infrastructure which relies on the electric grid, including wastewater treatment facilities, the information technology sector, and communications systems could be impacted. | Smart grid | Wikipedia | 382 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
The December 2015 Ukraine power grid cyberattack, the first recorded of its kind, disrupted services to nearly a quarter of a million people by bringing substations offline. The Council on Foreign Relations has noted that states are most likely to be the perpetrators of such an attack as they have access to the resources to carry one out despite the high level of difficulty of doing so. Cyber intrusions can be used as portions of a larger offensive, military or otherwise. Some security experts warn that this type of event is easily scalable to grids elsewhere. Insurance company Lloyd's of London has already modeled the outcome of a cyberattack on the Eastern Interconnection, which has the potential to impact 15 states, put 93 million people in the dark, and cost the country's economy anywhere from $243 billion to $1 trillion in various damages.
According to the U.S. House of Representatives Subcommittee on Economic Development, Public Buildings, and Emergency Management, the electric grid has already seen a sizable number of cyber intrusions, with two in every five aiming to incapacitate it. As such, the U.S. Department of Energy has prioritized research and development to decrease the electric grid's vulnerability to cyberattacks, citing them as an "imminent danger" in its 2017 Quadrennial Energy Review. The Department of Energy has also identified both attack resistance and self-healing as major keys to ensuring that today's smart grid is future-proof. While there are regulations already in place, namely the Critical Infrastructure Protection Standards introduced by the North America Electric Reliability Council, a significant number of them are suggestions rather than mandates. Most electricity generation, transmission, and distribution facilities and equipment are owned by private stakeholders, further complicating the task of assessing adherence to such standards. Additionally, even if utilities want to fully comply, they may find that it is too expensive to do so. | Smart grid | Wikipedia | 388 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
Some experts argue that the first step to increasing the cyber defenses of the smart electric grid is completing a comprehensive risk analysis of existing infrastructure, including research of software, hardware, and communication processes. Additionally, as intrusions themselves can provide valuable information, it could be useful to analyze system logs and other records of their nature and timing. Common weaknesses already identified using such methods by the Department of Homeland Security include poor code quality, improper authentication, and weak firewall rules. Once this step is completed, some suggest that it makes sense to then complete an analysis of the potential consequences of the aforementioned failures or shortcomings. This includes both immediate consequences as well as second- and third-order cascading effects on parallel systems. Finally, risk mitigation solutions, which may include simple remediation of infrastructure inadequacies or novel strategies, can be deployed to address the situation. Some such measures include recoding of control system algorithms to make them more able to resist and recover from cyberattacks or preventive techniques that allow more efficient detection of unusual or unauthorized changes to data. Strategies to account for human error which can compromise systems include educating those who work in the field to be wary of strange USB drives, which can introduce malware if inserted, even if just to check their contents.
Other solutions include utilizing transmission substations, constrained SCADA networks, policy based data sharing, and attestation for constrained smart meters.
Transmission substations utilize one-time signature authentication technologies and one-way hash chain constructs. These constraints have since been remedied with the creation of a fast-signing and verification technology and buffering-free data processing.
A similar solution has been constructed for constrained SCADA networks. This involves applying a Hash-Based Message Authentication Code to byte streams, converting the random-error detection available on legacy systems to a mechanism that guarantees data authenticity.
Policy-based data sharing utilizes GPS-clock-synchronized-fine-grain power grid measurements to provide increased grid stability and reliability. It does this through synchro-phasor requirements that are gathered by PMUs.
Attestation for constrained smart meters faces a slightly different challenge, however. One of the biggest issues with attestation for constrained smart meters is that in order to prevent energy theft, and similar attacks, cyber security providers have to make sure that the devices' software is authentic. To combat this problem, an architecture for constrained smart networks has been created and implemented at a low level in the embedded system. | Smart grid | Wikipedia | 507 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
The protection system of a smart grid provides grid reliability analysis, failure protection, and security and privacy protection services. While the additional communication infrastructure of a smart grid provides additional protective and security mechanisms, it also presents a risk of external attack and internal failures. In a report on cyber security of smart grid technology first produced in 2010, and later updated in 2014, the US National Institute of Standards and Technology pointed out that the ability to collect more data about energy use from customer smart meters also raises major privacy concerns, since the information stored at the meter, which is potentially vulnerable to data breaches, can be mined for personal details about customers.
Other challenges to adoption
Before a utility installs an advanced metering system, or any type of smart system, it must make a business case for the investment. Some components, like the power system stabilizers (PSS) installed on generators are very expensive, require complex integration in the grid's control system, are needed only during emergencies, and are only effective if other suppliers on the network have them. Without any incentive to install them, power suppliers don't. Most utilities find it difficult to justify installing a communications infrastructure for a single application (e.g. meter reading). Because of this, a utility must typically identify several applications that will use the same communications infrastructure – for example, reading a meter, monitoring power quality, remote connection and disconnection of customers, enabling demand response, etc. Ideally, the communications infrastructure will not only support near-term applications, but unanticipated applications that will arise in the future. Regulatory or legislative actions can also drive utilities to implement pieces of a smart grid puzzle. Each utility has a unique set of business, regulatory, and legislative drivers that guide its investments. This means that each utility will take a different path to creating their smart grid and that different utilities will create smart grids at different adoption rates.
Some features of smart grids draw opposition from industries that currently are, or hope to provide similar services. An example is competition with cable and DSL Internet providers from broadband over powerline internet access. Providers of SCADA control systems for grids have intentionally designed proprietary hardware, protocols and software so that they cannot inter-operate with other systems in order to tie its customers to the vendor. | Smart grid | Wikipedia | 462 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
The incorporation of digital communications and computer infrastructure with the grid's existing physical infrastructure poses challenges and inherent vulnerabilities. According to IEEE Security and Privacy Magazine, the smart grid will require that people develop and use large computer and communication infrastructure that supports a greater degree of situational awareness and that allows for more specific command and control operations. This process is necessary to support major systems such as demand-response wide-area measurement and control, storage and transportation of electricity, and the automation of electric distribution.
Power Theft / Power Loss
Various "smart grid" systems have dual functions. This includes Advanced Metering Infrastructure systems which, when used with various software can be used to detect power theft and by process of elimination, detect where equipment failures have taken place. These are in addition to their primary functions of eliminating the need for human meter reading and measuring the time-of-use of electricity.
The worldwide power loss including theft is estimated at two-hundred billion dollars annually.
Electricity theft also represents a major challenge when providing reliable electrical service in developing countries.
Deployments and attempted deployments
Enel
The earliest, and one of the largest, example of a smart grid is the Italian system installed by Enel S.p.A. of Italy. Completed in 2005, the Telegestore project was highly unusual in the utility world because the company designed and manufactured their own meters, acted as their own system integrator, and developed their own system software. The Telegestore project is widely regarded as the first commercial scale use of smart grid technology to the home, and delivers annual savings of 500 million euro at a project cost of 2.1 billion euro. | Smart grid | Wikipedia | 334 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
US Dept. of Energy - ARRA Smart Grid Project
One of the largest deployment programs in the world to-date is the U.S. Dept. of Energy's Smart Grid Program funded by the American Recovery and Reinvestment Act of 2009. This program required matching funding from individual utilities. A total of over $9 billion in Public/Private funds were invested as part of this program. Technologies included Advanced Metering Infrastructure, including over 65 million Advanced "Smart" Meters, Customer Interface Systems, Distribution & Substation Automation, Volt/VAR Optimization Systems, over 1,000 Synchrophasors, Dynamic Line Rating, Cyber Security Projects, Advanced Distribution Management Systems, Energy Storage Systems, and Renewable Energy Integration Projects. This program consisted of Investment Grants (matching), Demonstration Projects, Consumer Acceptance Studies, and Workforce Education Programs. Reports from all individual utility programs as well as overall impact reports will be completed by the second quarter of 2015.
In the U.S., the Energy Policy Act of 2005 and Title XIII of the Energy Independence and Security Act of 2007 are providing funding to encourage smart grid development. The objective is to enable utilities to better predict their needs, and in some cases involve consumers in a time-of-use tariff. Funds have also been allocated to develop more robust energy control technologies.
Austin, Texas
In the US, the city of Austin, Texas, has been working on building its smart grid since 2003, when its utility first replaced 1/3 of its manual meters with smart meters that communicate via a wireless mesh network. It currently manages 200,000 devices real-time (smart meters, smart thermostats, and sensors across its service area), and expects to be supporting 500,000 devices real-time in 2009 servicing 1 million consumers and 43,000 businesses.
Boulder, Colorado
Boulder, Colorado, completed the first phase of its smart grid project in August 2008. Both systems use the smart meter as a gateway to the home automation network (HAN) that controls smart sockets and devices. Some HAN designers favor decoupling control functions from the meter, out of concern of future mismatches with new standards and technologies available from the fast moving business segment of home electronic devices. | Smart grid | Wikipedia | 447 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
Hydro One
Hydro One, in Ontario, Canada is in the midst of a large-scale Smart Grid initiative, deploying a standards-compliant communications infrastructure from Trilliant. By the end of 2010, the system will serve 1.3 million customers in the province of Ontario. The initiative won the "Best AMR Initiative in North America" award from the Utility Planning Network.
Île d'Yeu
Île d'Yeu began a 2-year pilot program in Spring of 2020. Twenty-three houses in the Ker Pissot neighborhood and surrounding areas were interconnected with a microgrid that was automated as a smart grid with software from Engie. Sixty-four solar panels with a peak capacity of 23.7 kW were installed on five houses and a battery with a storage capacity of 15 kWh was installed on one house. Six houses store excess solar energy in their hot water heaters. A dynamic system apportions the energy provided by the solar panels and stored in the battery and hot water heaters to the system of 23 houses. The smart grid software dynamically updates energy supply and demand in 5 minute intervals, deciding whether to pull energy from the battery or from the panels and when to store it in the hot water heaters. This pilot program was the first such project in France.
Mannheim
The City of Mannheim in Germany is using realtime Broadband Powerline (BPL) communications in its Model City Mannheim "MoMa" project.
Sydney
Sydney also in Australia, in partnership with the Australian Government implemented the Smart Grid, Smart City program.
Évora
InovGrid is an innovative project in Évora, Portugal that aims to equip the electricity grid with information and devices to automate grid management, improve service quality, reduce operating costs, promote energy efficiency and environmental sustainability, and increase the penetration of renewable energies and electric vehicles. It will be possible to control and manage the state of the entire electricity distribution grid at any given instant, allowing suppliers and energy services companies to use this technological platform to offer consumers information and added-value energy products and services. This project to install an intelligent energy grid places Portugal and EDP at the cutting edge of technological innovation and service provision in Europe.
E-Energy
In the so-called E-Energy projects several German utilities are creating first nucleolus in six independent model regions. A technology competition identified this model regions to carry out research and development activities with the main objective to create an "Internet of Energy." | Smart grid | Wikipedia | 500 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
Massachusetts
One of the first attempted deployments of "smart grid" technologies in the United States was rejected in 2009 by electricity regulators in the Commonwealth of Massachusetts, a US state. According to an article in the Boston Globe, Northeast Utilities' Western Massachusetts Electric Co. subsidiary actually attempted to create a "smart grid" program using public subsidies that would switch low income customers from post-pay to pre-pay billing (using "smart cards") in addition to special hiked "premium" rates for electricity used above a predetermined amount. This plan was rejected by regulators as it "eroded important protections for low-income customers against shutoffs". According to the Boston Globe, the plan "unfairly targeted low-income customers and circumvented Massachusetts laws meant to help struggling consumers keep the lights on". A spokesman for an environmental group supportive of smart grid plans and Western Massachusetts' Electric's aforementioned "smart grid" plan, in particular, stated "If used properly, smart grid technology has a lot of potential for reducing peak demand, which would allow us to shut down some of the oldest, dirtiest power plants... It's a tool."
eEnergy Vermont consortium
The eEnergy Vermont consortium is a US statewide initiative in Vermont, funded in part through the American Recovery and Reinvestment Act of 2009, in which all of the electric utilities in the state have rapidly adopted a variety of Smart Grid technologies, including about 90% Advanced Metering Infrastructure deployment, and are presently evaluating a variety of dynamic rate structures.
Netherlands
In the Netherlands a large-scale project (>5000 connections, >20 partners) was initiated to demonstrate integrated smart grids technologies, services and business cases. | Smart grid | Wikipedia | 347 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
Chattanooga
EPB in Chattanooga, TN is a municipally-owned electric utility that started construction of a smart grid in 2008, receiving a $111,567,606 grant from the US DOE in 2009 to expedite construction and implementation (for a total budget of $232,219,350). Deployment of power-line interrupters (1170 units) was completed in April 2012, and deployment of smart meters (172,079 units) was completed in 2013. The smart grid's backbone fiber-optic system was also used to provide the first gigabit-speed internet connection to residential customers in the US through the Fiber to the Home initiative, and now speeds of up to 10 gigabits per second are available to residents. The smart grid is estimated to have reduced power outages by an average of 60%, saving the city about 60 million dollars annually. It has also reduced the need for "truck rolls" to scout and troubleshoot faults, resulting in an estimated reduction of 630,000 truck driving miles, and 4.7 million pounds of carbon emissions. In January 2016, EPB became the first major power distribution system to earn Performance Excellence in Electricity Renewal (PEER) certification.
OpenADR Implementations
Certain deployments utilize the OpenADR standard for load shedding and demand reduction during higher demand periods.
China
The smart grid market in China is estimated to be $22.3 billion with a projected growth to $61.4 billion by 2015. Honeywell is developing a demand response pilot and feasibility study for China with the State Grid Corp. of China using the OpenADR demand response standard. The State Grid Corp., the Chinese Academy of Science, and General Electric intend to work together to develop standards for China's smart grid rollout.
United States
In 2009, the US Department of Energy awarded an $11 million grant to Southern California Edison and Honeywell for a demand response program that automatically turns down energy use during peak hours for participating industrial customers. The Department of Energy awarded an $11.4 million grant to Honeywell to implement the program using the OpenADR standard.
Hawaiian Electric Co. (HECO) is implementing a two-year pilot project to test the ability of an ADR program to respond to the intermittence of wind power. Hawaii has a goal to obtain 70 percent of its power from renewable sources by 2030. HECO will give customers incentives for reducing power consumption within 10 minutes of a notice. | Smart grid | Wikipedia | 501 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
Guidelines, standards and user groups
Part of the IEEE Smart Grid Initiative, IEEE 2030.2 represents an extension of the work aimed at utility storage systems for transmission and distribution networks. The IEEE P2030 group expects to deliver early 2011 an overarching set of guidelines on smart grid interfaces. The new guidelines will cover areas including batteries and supercapacitors as well as flywheels. The group has also spun out a 2030.1 effort drafting guidelines for integrating electric vehicles into the smart grid.
IEC TC 57 has created a family of international standards that can be used as part of the smart grid. These standards include IEC 61850 which is an architecture for substation automation, and IEC 61970/61968 – the Common Information Model (CIM). The CIM provides for common semantics to be used for turning data into information.
OpenADR is an open-source smart grid communications standard used for demand response applications.
It is typically used to send information and signals to cause electrical power-using devices to be turned off during periods of higher demand.
MultiSpeak has created a specification that supports distribution functionality of the smart grid. MultiSpeak has a robust set of integration definitions that supports nearly all of the software interfaces necessary for a distribution utility or for the distribution portion of a vertically integrated utility. MultiSpeak integration is defined using extensible markup language (XML) and web services.
The IEEE has created a standard to support synchrophasors – C37.118.
The UCA International User Group discusses and supports real world experience of the standards used in smart grids.
A utility task group within LonMark International deals with smart grid related issues.
There is a growing trend towards the use of TCP/IP technology as a common communication platform for smart meter applications, so that utilities can deploy multiple communication systems, while using IP technology as a common management platform.
IEEE P2030 is an IEEE project developing a "Draft Guide for Smart Grid Interoperability of Energy Technology and Information Technology Operation with the Electric Power System (EPS), and End-Use Applications and Loads".
NIST has included ITU-T G.hn as one of the "Standards Identified for Implementation" for the Smart Grid "for which it believed there
was strong stakeholder consensus". G.hn is standard for high-speed communications over power lines, phone lines and coaxial cables. | Smart grid | Wikipedia | 494 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
OASIS EnergyInterop' – An OASIS technical committee developing XML standards for energy interoperation. Its starting point is the California OpenADR standard.
Under the Energy Independence and Security Act of 2007 (EISA), NIST is charged with overseeing the identification and selection of hundreds of standards that will be required to implement the Smart Grid in the U.S. These standards will be referred by NIST to the Federal Energy Regulatory Commission (FERC). This work has begun, and the first standards have already been selected for inclusion in NIST's Smart Grid catalog. However, some commentators have suggested that the benefits that could be realized from Smart Grid standardization could be threatened by a growing number of patents that cover Smart Grid architecture and technologies. If patents that cover standardized Smart Grid elements are not revealed until technology is broadly distributed throughout the network ("locked-in"), significant disruption could occur when patent holders seek to collect unanticipated rents from large segments of the market.
GridWise Alliance rankings
In November 2017 the non-profit GridWise Alliance along with Clean Edge Inc., a clean energy group, released rankings for all 50 states in their efforts to modernize the electric grid. California was ranked number one. The other top states were Illinois, Texas, Maryland, Oregon, Arizona, the District of Columbia, New York, Nevada and Delaware. "The 30-plus page report from the GridWise Alliance, which represents stakeholders that design, build and operate the electric grid, takes a deep dive into grid modernization efforts across the country and ranks them by state." | Smart grid | Wikipedia | 320 | 13201685 | https://en.wikipedia.org/wiki/Smart%20grid | Technology | Electricity transmission and distribution | null |
Turritopsis dohrnii, also known as the immortal jellyfish, is a species of small, biologically immortal jellyfish found worldwide in temperate to tropic waters. It is one of the few known cases of animals capable of reverting completely to a sexually immature, colonial stage after having reached sexual maturity as a solitary individual.
Like most other hydrozoans, T. dohrnii begin their lives as tiny, free-swimming larvae known as planulae. As a planula settles down, it gives rise to a colony of polyps that are attached to the sea floor. All the polyps and jellyfish arising from a single planula are genetically identical clones. The polyps form into an extensively branched form, which is not commonly seen in most jellyfish. Jellyfish, also known as medusae, then bud off these polyps and continue their life in a free-swimming form, eventually becoming sexually mature. When sexually mature, they have been known to prey on other jellyfish species at a rapid pace. If the T. dohrnii jellyfish is exposed to environmental stress, physical assault, or is sick or old, it can revert to the polyp stage, forming a new polyp colony. It does this through the cell development process of transdifferentiation, which alters the differentiated state of the cells and transforms them into new types of cells.
Theoretically, this process can go on indefinitely, effectively rendering the jellyfish biologically immortal, although in practice individuals can still die. In nature, most Turritopsis dohrnii are likely to succumb to predation or disease in the medusa stage without reverting to the polyp form.
The capability of biological immortality with no maximum lifespan makes T. dohrnii an important target of basic biological aging and pharmaceutical research.
Taxonomy
The species was formerly considered conspecific with T. nutricula before being reclassified as a separate species. It was named in 1883 in honour of Anton Dohrn, the founder of the Stazione Zoologica Anton Dohrn in Naples, Italy.
Until a 2006 study, it was thought that Turritopsis rubra and Turritopsis nutricula were the same species as Turritopsis dohrnii. It is not known whether or not T. rubra medusae can also transform back into polyps, however further research is still to be done.
Description | Turritopsis dohrnii | Wikipedia | 506 | 9214162 | https://en.wikipedia.org/wiki/Turritopsis%20dohrnii | Biology and health sciences | Cnidarians | Animals |
The medusa of Turritopsis dohrnii is bell-shaped, with a maximum diameter of about and is about as tall as it is wide. The mesoglea in the walls of the bell is uniformly thin, except for some thickening at the apex. The relatively large stomach is bright red and has a cruciform shape in cross section. Young specimens 1 mm in diameter have only eight tentacles evenly spaced out along the edge, whereas adult specimens have 80–90 tentacles. The medusa (jellyfish) is free-living in the plankton. Dense nerve net cells are also present in the epidermis in the cap. They form a large ring-like structure above the radial canal commonly presented in cnidarians.
Turritopsis dohrnii also has a bottom-living polyp form, or hydroid, which consists of stolons that run along the substrate and upright branches with feeding polyps that can produce medusa buds. These polyps develop over a few days into tiny 1 mm medusae, which are liberated and swim free from the parent hydroid colony.
Distribution and invasion
Turritopsis is believed to have originated in the Pacific, but has spread all over the world through trans-Arctic migrations, and has speciated into several populations that are easy to distinguish morphologically, but whose species distinctions have recently been verified by a study and comparison of mitochondrial ribosomal gene sequences. Turritopsis are found in temperate to tropical regions in all of the world's oceans. Turritopsis is believed to be spreading across the world through ballast water discharge. Unlike other species invasions which caused serious economic and ecological consequences, T. dohrnii's invasion around the world was unnoticed due to their tiny size and innocuity. "We are looking at a worldwide silent invasion", said Smithsonian Tropical Marine Institute scientist Maria Miglietta.
Life cycle | Turritopsis dohrnii | Wikipedia | 390 | 9214162 | https://en.wikipedia.org/wiki/Turritopsis%20dohrnii | Biology and health sciences | Cnidarians | Animals |
The eggs develop in gonads of female medusae, which are located in the walls of the manubrium (stomach). Mature eggs are presumably spawned and fertilized in the sea by sperm produced and released by male medusae, as is the case for most hydromedusae. However, the related species Turritopsis rubra seems to retain fertilized eggs until the planula stage. Fertilized eggs develop into planula larvae, which settle onto the sea floor (or even the rich marine communities that live on floating docks), and develop into polyp colonies (hydroids). The hydroids bud new jellyfishes, which are released at about one millimetre in size and then grow and feed in the plankton, becoming sexually mature after a few weeks (the exact duration depends on the ocean temperature; at it is 25 to 30 days and at it is 18 to 22 days). Medusae of T. dohrnii are able to survive between 14 °C and 25 °C.
Biological immortality
Most jellyfish species have a relatively fixed lifespan, which varies by species from hours to many months (long-lived mature jellyfish spawn every day or night; the time is also fairly fixed and species-specific). The medusa of Turritopsis dohrnii is the only form known to have the ability to return to a polyp state, by a specific transformation process that requires the presence of certain cell types (tissue from both the jellyfish bell surface and the circulatory canal system). | Turritopsis dohrnii | Wikipedia | 319 | 9214162 | https://en.wikipedia.org/wiki/Turritopsis%20dohrnii | Biology and health sciences | Cnidarians | Animals |
Experiments have revealed that all stages of the medusae, from newly released to fully mature individuals, can transform back into polyps under the conditions of starvation, sudden temperature change, reduction of salinity, and artificial damage of the bell with forceps or scissors. The transforming medusa is characterized first by deterioration of the bell, mesoglea, and tentacles. All immature medusa (with 12 tentacles at most) then turned into a cyst-like stage and then transformed into stolons and polyps. However, about 20%-40% of mature medusa went into the stolons and polyps stage without passing the cyst-like stage. Polyps were formed after 2 days since stolons had developed and fed on food. Polyps further multiply by growing additional stolons, branches, and then polyps to form colonial hydroids. In the experiment, they would eventually transform into stolons and polyps and begin their lives once again, even without environmental changes or injury.
This ability to reverse the biotic cycle (in response to adverse conditions) is unique in the animal kingdom. It allows the jellyfish to bypass death, rendering Turritopsis dohrnii potentially biologically immortal. The process has not been observed in their natural habitat, in part because the process is quite rapid and because field observations at the right moment are unlikely. Regardless, most individual medusae are likely to fall victim to the general hazards of life as mesoplankton, including being eaten by predators or succumbing to disease.
The species possesses unique mechanisms related to telomere maintenance, which play a significant role in its regenerative abilities. T. dohrnii maintains telomere length through specific cellular processes during its life cycle reversal, effectively resetting cellular aging.
The species' cell development method of transdifferentiation has inspired scientists to find a way to make stem cells using this process for renewing damaged or dead tissue in humans.
Ecology | Turritopsis dohrnii | Wikipedia | 409 | 9214162 | https://en.wikipedia.org/wiki/Turritopsis%20dohrnii | Biology and health sciences | Cnidarians | Animals |
Diet
Turritopsis dohrnii are a carnivorous species that commonly feed on zooplankton. Their diet mainly consists of plankton, fish eggs and small mollusks. T. dohrnii ingests food and excretes waste through the mouth. T. dohrnii hunts by using its tentacles as it drifts through the water. Its tentacles, which contain stinging cells called nematocysts, spread and sting its prey. The tentacles can then flex to direct its prey to the mouth. T. dohrnii, like other jellyfish, may use its bell to catch its prey. T. dohrnii's bell will expand, sucking in water, as it propels itself to swim. This expansion of the bell brings potential prey in closer reach of the tentacles.
Predation
Turritopsis dohrnii, like other jellyfish, are preyed on most commonly by other jellyfish. Other predators of T. dohrnii include sea anemones, tuna, sharks, swordfish, sea turtles, and penguins. Many species prey on T. dohrnii and other jellyfish due to their simple composition. They are only approximately 5% non-aqueous matter, and the remaining part is composed of water. They are composed of three layers. An outer layer (the epidermis), a middle layer (mesoglea; a thick, jelly-like substance), and an inner layer (gastrodermis).
Habitat
Turritopsis dohrnii was first discovered in the Mediterranean Sea, but has since been found worldwide. T. dohrnii is generally found living in temperate to tropical waters. They can be found in marinas or docks, on vessel hulls, and on the ocean floor. They typically live in a salinity range of polyhaline (18–30 PSU) and euhaline (30-40 PSU).
Genomic analysis
Genomic analyses such as sequence analysis on mRNA or mitochondria DNA have been employed to investigate its lifecycle. mRNA analysis of each life stage showed that a stage-specific gene in the medusae stage is expressed tenfold more than in other stages. This gene is relative to a Wnt signal that can induce a regeneration process upon injury. | Turritopsis dohrnii | Wikipedia | 480 | 9214162 | https://en.wikipedia.org/wiki/Turritopsis%20dohrnii | Biology and health sciences | Cnidarians | Animals |
Analysis of nucleotide sequence homologs and protein homologs identified Nemopsis bachei as the species' closest relative. None of the closely related species display biological immortality.
In 2022, a study reported the key molecular mechanisms of rejuvenation they found in a comparison of the newly presented genomes of this biologically immortal jellyfish and a similar but non-rejuvenating jellyfish, involving e.g. DNA replication and repair, and stem cell renewal.
Culturing
Keeping T. dohrnii in captivity is quite difficult. Currently, only one scientist, Shin Kubota from Kyoto University, has managed to sustain a group of these jellyfish for a prolonged period of time. The plankton must be inspected daily to ensure that they have properly digested the Artemia cysts they are being fed.
Kubota reported that during a two-year period, his colony rebirthed itself 11 times. Kubota regularly appears on Japanese television to talk about his immortal jellyfish and has recorded several songs about them, often singing them at the end of his conference presentations. | Turritopsis dohrnii | Wikipedia | 224 | 9214162 | https://en.wikipedia.org/wiki/Turritopsis%20dohrnii | Biology and health sciences | Cnidarians | Animals |
In chemistry, transition state theory (TST) explains the reaction rates of elementary chemical reactions. The theory assumes a special type of chemical equilibrium (quasi-equilibrium) between reactants and activated transition state complexes.
TST is used primarily to understand qualitatively how chemical reactions take place. TST has been less successful in its original goal of calculating absolute reaction rate constants because the calculation of absolute reaction rates requires precise knowledge of potential energy surfaces, but it has been successful in calculating the standard enthalpy of activation (ΔH‡, also written Δ‡Hɵ), the standard entropy of activation (ΔS‡ or Δ‡Sɵ), and the standard Gibbs energy of activation (ΔG‡ or Δ‡Gɵ) for a particular reaction if its rate constant has been experimentally determined (the ‡ notation refers to the value of interest at the transition state; ΔH‡ is the difference between the enthalpy of the transition state and that of the reactants).
This theory was developed simultaneously in 1935 by Henry Eyring, then at Princeton University, and by Meredith Gwynne Evans and Michael Polanyi of the University of Manchester. TST is also referred to as "activated-complex theory", "absolute-rate theory", and "theory of absolute reaction rates".
Before the development of TST, the Arrhenius rate law was widely used to determine energies for the reaction barrier. The Arrhenius equation derives from empirical observations and ignores any mechanistic considerations, such as whether one or more reactive intermediates are involved in the conversion of a reactant to a product. Therefore, further development was necessary to understand the two parameters associated with this law, the pre-exponential factor (A) and the activation energy (Ea). TST, which led to the Eyring equation, successfully addresses these two issues; however, 46 years elapsed between the publication of the Arrhenius rate law, in 1889, and the Eyring equation derived from TST, in 1935. During that period, many scientists and researchers contributed significantly to the development of the theory.
Theory
The basic ideas behind transition state theory are as follows: | Transition state theory | Wikipedia | 445 | 9217017 | https://en.wikipedia.org/wiki/Transition%20state%20theory | Physical sciences | Kinetics | Chemistry |
Rates of reaction can be studied by examining activated complexes near the saddle point of a potential energy surface. The details of how these complexes are formed are not important. The saddle point itself is called the transition state.
The activated complexes are in a special equilibrium (quasi-equilibrium) with the reactant molecules.
The activated complexes can convert into products, and kinetic theory can be used to calculate the rate of this conversion.
Development
In the development of TST, three approaches were taken as summarized below.
Thermodynamic treatment
In 1884, Jacobus van 't Hoff proposed the Van 't Hoff equation describing the temperature dependence of the equilibrium constant for a reversible reaction:
{A} <=> {B}
where ΔU is the change in internal energy, K is the equilibrium constant of the reaction, R is the universal gas constant, and T is thermodynamic temperature. Based on experimental work, in 1889, Svante Arrhenius proposed a similar expression for the rate constant of a reaction, given as follows:
Integration of this expression leads to the Arrhenius equation
where k is the rate constant. A was referred to as the frequency factor (now called the pre-exponential coefficient), and Ea is regarded as the activation energy. By the early 20th century many had accepted the Arrhenius equation, but the physical interpretation of A and Ea remained vague. This led many researchers in chemical kinetics to offer different theories of how chemical reactions occurred in an attempt to relate A and Ea to the molecular dynamics directly responsible for chemical reactions.
In 1910, French chemist René Marcelin introduced the concept of standard Gibbs energy of activation. His relation can be written as
At about the same time as Marcelin was working on his formulation, Dutch chemists Philip Abraham Kohnstamm, Frans Eppo Cornelis Scheffer, and Wiedold Frans Brandsma introduced standard entropy of activation and the standard enthalpy of activation. They proposed the following rate constant equation
However, the nature of the constant was still unclear.
Kinetic-theory treatment
In early 1900, Max Trautz and William Lewis studied the rate of the reaction using collision theory, based on the kinetic theory of gases. Collision theory treats reacting molecules as hard spheres colliding with one another; this theory neglects entropy changes, since it assumes that the collision between molecules are completely elastic.
Lewis applied his treatment to the following reaction and obtained good agreement with experimental result.
2 HI → H2 + I2 | Transition state theory | Wikipedia | 509 | 9217017 | https://en.wikipedia.org/wiki/Transition%20state%20theory | Physical sciences | Kinetics | Chemistry |
However, later when the same treatment was applied to other reactions, there were large discrepancies between theoretical and experimental results.
Statistical-mechanical treatment
Statistical mechanics played a significant role in the development of TST. However, the application of statistical mechanics to TST was developed very slowly given the fact that in mid-19th century, James Clerk Maxwell, Ludwig Boltzmann, and Leopold Pfaundler published several papers discussing reaction equilibrium and rates in terms of molecular motions and the statistical distribution of molecular speeds.
It was not until 1912 when the French chemist A. Berthoud used the Maxwell–Boltzmann distribution law to obtain an expression for the rate constant.
where a and b are constants related to energy terms.
Two years later, René Marcelin made an essential contribution by treating the progress of a chemical reaction as a motion of a point in phase space. He then applied Gibbs' statistical-mechanical procedures and obtained an expression similar to the one he had obtained earlier from thermodynamic consideration.
In 1915, another important contribution came from British physicist James Rice. Based on his statistical analysis, he concluded that the rate constant is proportional to the "critical increment". His ideas were further developed by Richard Chace Tolman. In 1919, Austrian physicist Karl Ferdinand Herzfeld applied statistical mechanics to the equilibrium constant and kinetic theory to the rate constant of the reverse reaction, k−1, for the reversible dissociation of a diatomic molecule.
AB <=>[k_1][k_{-1}] {A} + {B}
He obtained the following equation for the rate constant of the forward reaction
where is the dissociation energy at absolute zero, kB is the Boltzmann constant, h is the Planck constant, T is thermodynamic temperature, is vibrational frequency of the bond.
This expression is very important since it is the first time that the factor kBT/h, which is a critical component of TST, has appeared in a rate equation.
In 1920, the American chemist Richard Chace Tolman further developed Rice's idea of the critical increment. He concluded that critical increment (now referred to as activation energy) of a reaction is equal to the average energy of all molecules undergoing reaction minus the average energy of all reactant molecules. | Transition state theory | Wikipedia | 476 | 9217017 | https://en.wikipedia.org/wiki/Transition%20state%20theory | Physical sciences | Kinetics | Chemistry |
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