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SVET ( Russian : свет , "light") was a plant cultivation unit on the Kristall module of the Mir space station. It was installed in 1990 and operated until 2001. [ 1 ] Brassica rapa was successfully grown there in 1997. [ 2 ] [ 3 ]
The project was a joint Russian-Bulgarian one, developed at the Space Research and Technology Institute in Sofia . [ 4 ]
This astrobiology -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/SVET_plant_growth_system |
The SVI-838 , also known as X'press 16 , is the last microcomputer produced by Spectravideo (at Hong Kong ). Although it was a PC clone , it had the standard sound and video coprocessors of the MSX2 , making it a hybrid system. [ 1 ] The sales were unimpressive and it is now considered a collectible .
With a SVI-811 adapter, the machine could run MSX 1 programs in cartridge . [ 1 ]
The SVI-838 had the following technical specifications:
Main items: [ 2 ]
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/SVI-838 |
SWAT ( soil and water assessment tool ) is a river basin scale model developed to quantify the impact of land management practices in large, complex watersheds. SWAT is a public domain software enabled model actively supported by the USDA Agricultural Research Service at the Blackland Research & Extension Center in Temple, Texas , USA. [ 1 ] It is a hydrology model with the following components: weather, surface runoff , return flow, percolation, evapotranspiration , transmission losses, pond and reservoir storage, crop growth and irrigation, groundwater flow, reach routing , nutrient and pesticide loading, and water transfer. SWAT can be considered a watershed hydrological transport model . This model is used worldwide [ 2 ] and is continuously under development. As of July 2012, more than 1000 peer-reviewed articles have been published [ 3 ] that document its various applications.
SWAT is a continuous time model that operates on a daily time step at basin scale. The objective of such a model is to predict the long-term impacts in large basins of management and also timing of agricultural practices within a year (i.e., crop rotations, planting and harvest dates, irrigation, fertilizer, and pesticide application rates and timing).
It can be used to simulate at the basin scale water and nutrients cycle in landscapes whose dominant land use is agriculture. It can also help in assessing the environmental efficiency of best management practices and alternative management policies. SWAT uses a two-level dissagregation scheme; a preliminary subbasin identification is carried out based on topographic criteria, followed by further discretization using land use and soil type considerations. Areas with the same soil type and land use form a Hydrologic Response Unit (HRU), a basic computational unit assumed to be homogeneous in hydrologic response to land cover change. | https://en.wikipedia.org/wiki/SWAT_model |
SWEPOS is a support system for accurate measurement of Swedish geography using a network of fixed reference stations which gather GNSS data. The SWEPOS system permits mobile GPS / GLONASS [ 1 ] receivers to receive detailed positioning data down to the centimeter level. The SWEPOS network of reference stations began as a co-operation between the National Land Survey of Sweden and Onsala Space Observatory . [ 2 ] | https://en.wikipedia.org/wiki/SWEPOS |
SWISS TXT (SWISS TXT Corporation) (until December 2015: SWISS TXT Schweizerische Teletext AG) is a subsidiary and the centre of multimedia expertise of the Swiss Broadcasting Corporation . [ 1 ] [ 2 ]
The company was founded on 23 December 1983 with a licence granted by the Swiss Federal Council Teletext Licence. [ 3 ]
The Teletext service started operations on SF DRS in 1984, on TSR in 1985 and on TSI in 1986. [ 4 ] In 2001, the number of daily viewers reached a record of 1.17 million. In 2004, that number reached 1.3 million a day. [ 5 ]
Until 2015, SWISS TXT was responsible for the development, operation and commercialization of the Teletext service on television channels operated by the Swiss Broadcasting Corporation . Between 2005 and 2008, the Teletext editorial department was integrated into Swiss Broadcasting Corporation television channels SRF 1 , SRF zwei , RTS Un , RTS Deux , RSI La 1 , RSI La 2 operations.
The multimedia sector was expanded in 2009. [ 6 ] With the strategic reorientation on 1 January 2016, SWISS TXT operates in multimedia for the Swiss Broadcasting Corporation and on the third-party market. [ 7 ]
SWISS TXT has its headquarters in Biel/Bienne and branch offices in Zürich , Bern , Geneva , Lausanne and Comano .
SWISS TXT subtitles the Swiss Broadcasting Corporation television programmes. [ 8 ] It also provides transcription, translation and audio description services. [ 9 ] | https://en.wikipedia.org/wiki/SWISS_TXT |
SWORD ( Simple Web-service Offering Repository Deposit ) is an interoperability standard that allows digital repositories to accept the deposit of content from multiple sources in different formats (such as XML documents) via a standardized protocol . In the same way that the HTTP protocol allows any web browser to talk to any web server , so SWORD allows clients to talk to repository servers . SWORD is a profile (specialism) of the Atom Publishing Protocol , but restricts itself solely to the scope of depositing resources into scholarly systems.
The first version of the SWORD protocol was created in 2007 by a consortium of UK institutional repository experts. The project to develop SWORD was funded by the JISC and managed by UKOLN . [ 1 ] An overview of the initial development of SWORD is given in "SWORD: Simple Web-service Offering Repository Deposit." [ 2 ] The standard grew out of a need for an interoperable method by which resources could be deposited into repositories. Interoperable standards existed to allow the harvesting of content (e.g. Open Archives Initiative Protocol for Metadata Harvesting ) or for searching (e.g. OpenSearch ) but not for deposit.
Between the original release in 2007, two subsequent projects were undertaken until 2009 to further refine the version 1.0 specification and perform advocacy work. The resulting release was numbered 1.3. [ 3 ] Further descriptions of the work is available in Lewis et al., "If SWORD is the answer, what is the question? Use of the Simple Web service Offering Repository Deposit protocol." [ 4 ]
In 2011 a new project began to extend the "fire and forget" approach of the SWORD 1.x specification into a full CRUD (Create, Retrieve, Update, Delete) interface, and the result was a new version (designated 2.0). [ 5 ] This was followed by extensive development work on client environments in several programming languages, and incorporation into the development of several Jisc -funded efforts. [ 6 ] [ 7 ]
Many different use cases exist [ 8 ] where it may be desirable to remotely deposit resources into scholarly systems. These include:
Three categories of implementation exist: repository implementations for existing repository servers , client implementations that can be used to perform SWORD deposits, and code libraries to assist in the creation of new SWORD clients or servers.
The following digital repositories are SWORD compliant:
The SWORD Course [ 24 ] | https://en.wikipedia.org/wiki/SWORD_(protocol) |
A standing wave ratio meter , SWR meter , ISWR meter (current " I " SWR), or VSWR meter (voltage SWR) measures the standing wave ratio (SWR) in a transmission line . [ a ] The meter indirectly measures the degree of mismatch between a transmission line and its load (usually an antenna ). Electronics technicians use it to adjust radio transmitters and their antennas and feedlines to be impedance matched so they work together properly, and evaluate the effectiveness of other impedance matching efforts.
A directional SWR meter measures the magnitude of the forward and reflected waves by sensing each one individually, with directional couplers . A calculation then produces the SWR.
Referring to the above diagram, the transmitter (TX) and antenna (ANT) terminals connect via an internal transmission line. This main line is electromagnetically coupled to two smaller sense lines (directional couplers). These are terminated with resistors at one end and diode rectifiers at the other. Some meters use a printed circuit board with three parallel traces to make the transmission line and two sensing lines. The resistors match the characteristic impedance of the sense lines. The diodes convert the magnitudes of the forward and reverse waves to the terminals FWD and REV, respectively, as DC voltages, which are smoothed by the capacitors. [ 1 ] : 27‑21 The meter or amplifier (not shown) connected to the FWD and REV terminals acts as the required drain resistor, and determines the dwell-time of the meter reading.
To calculate the SWR, first calculate the reflection coefficient:
(the voltages should include a relative phase factor).
Then calculate the SWR:
In a passive meter, this is usually indicated on a non-linear scale.
For decades [ 2 ] [ 3 ] radio operators have built and used SWR meters as a simple tuning and diagnostic tool. With shielding compromised, a pair of coax or twin line transmission lines, placed close enough, suffer crosstalk . A wave moving in the driven line induces waves in the measurement line. Placed in parallel (straight or loosely coiled) a driven wave reinforces or cancels an induced wave in the same or opposite direction. If the cable pair exceeds half wavelength, cancellation is complete, and power dissipated in matched termination is approximately proportional to the forward and reflected power.
The approximation improves as crosstalk weakens and harmonic number increases. Over time, nonlinear high gain amplifiers have replaced nonlinear electro-mechanical movements – which replaced incandescent bulbs – to require less cross-talk and improve linear frequency range.
Because all frequencies above minimum contribute, the measured ratio is a single frequency quality measure, that increases with unintended harmonics and spurious emissions, as well as actual SWR. By analogy, the measurement cable is a crystal radio (non-discriminating receiver) representing all the radio receivers that might suffer interference from dirty emissions. Though called an SWR Meter, a low measured ratio indicates not only good match, but also clean A3, F3, or G3 emission without excessive harmonics nor spurious (out-of-channel) power.
SWR can also be measured using an impedance bridge . The bridge is balanced (0 Volts across the detector) only when the test impedance exactly matches the reference impedance. When a transmission line is mismatched ( SWR > 1:1 ), its input impedance deviates from its characteristic impedance; thus, a bridge can be used to determine the presence or absence of a low SWR.
To test for a match, the reference impedance of the bridge is set to the expected load impedance (for example, 50 Ohms), and the transmission line connected as the unknown impedance. RF power is applied to the circuit. The voltage at the line input represents the vector sum of the forward wave, and the wave reflected from the load. If we know the characteristic impedance of the line is 50 Ohms, we know the magnitude and phase of the forward wave. It's the same wave present on the other side of the detector. Subtracting this known wave from the wave at the line input yields the reflected wave. Properly designed, a bridge circuit can not only indicate a match, but the degree of mismatch – making it possible to calculate the SWR. This usually involves alternately connecting the reference wave and the reflected wave to a power meter, and comparing the magnitudes of the resulting deflections. [ 1 ] : 27‑03
An SWR meter does not measure the actual impedance of a load (the resistance and reactance), but only the mismatch ratio. To measure the actual impedance requires an antenna analyzer or other similar RF measuring device. For accurate readings, the SWR meter itself must also match the line's impedance (typically 50 or 75 Ohms). To accommodate multiple impedances, some SWR meters have switches that select the impedance appropriate for the sense lines.
An SWR meter should connect to the line as close as possible to the antenna: All practical transmission lines have a certain amount of loss, which attenuates the reflected wave as it travels back along the line. Thus, the SWR is highest closest to the load, and only improves as the distance from the load increases, creating the false impression of a matched system. [ 1 ] : 28‑07 | https://en.wikipedia.org/wiki/SWR_meter |
SX000i - International guide for the use of the S-Series of Integrated Logistics Support (ILS) specifications , is a specification developed jointly by a multinational team from the AeroSpace and Defence Industries Association of Europe (ASD) and Aerospace Industries Association (AIA). [ 1 ] SX000i is part of the S-Series of ILS specifications .
SX000i provides information, guidance and instructions to ensure compatibility and the commonality of Integrated Logistics Support (ILS) processes among the S-Series suite of ILS specifications jointly developed by both associations.
By defining common logistics processes to be used across all S-Series ILS specifications and the interactions of the current S-Series ILS specifications with the logistics processes, the SX000i forms the basis for sharing and exchanging data securely through the life of products and services, not only within the support domain, but also with other domains such as Engineering. [ 2 ] The SX000i also provides governance for the maintenance of current S-Series ILS specifications and the development of new S-Series ILS specifications.
SX000i builds on existing standards and specifications so as to provide a unified view of sometimes contradictory ILS specifications and publications. [ 3 ] [ 4 ] [ 5 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ] [ 10 ] [ 11 ] [ 12 ] [ 13 ] [ 14 ] [ 15 ] [ 16 ] [ 17 ] [ excessive citations ] A reference and mapping of SX000i to these documents has been provided in Chapter 6.
SX000i provides a guide for the use of the S-series ILS specifications by ILS managers and practitioners, as well as for the management and future development of the specifications by the ILS specification Council and ILS specification Steering Committees (SC) and Working Groups (WG).
SX000i:
During the development of the S-Series ILS specifications, the different ASD/AIA Steering Committees and Working Groups identified the need for an "umbrella" specification to ensure the compatibility and commonality of ILS processes among the S-Series ILS specifications.
In 2011, the decision was made to develop, publicize and maintain an Integrated Logistics Support Guide, named SX000i, so as to provide a compatible and common ILS process to be used in the other S-Series ILS specifications. Development of SX000i was viewed by the ILS Specifications Council as an essential step to achieve the vision for the S-Series ILS specifications.
In June 2011, the SX000i working group was formed and SX000i development started. The current title of SX000i, International guide for the use of the S-Series of Integrated Logistics Support (ILS) specifications, was approved by the ASD/AIA ILS Specifications Council in June 2012.
Following the creation of the SX000i working group, the ASD/AIA Data Model and Exchange Working Group (DMEWG) was formed under the ILS Specifications Council in October 2011. Working in close cooperation with the SX000i team, the DMEWG coordinates the data modeling activities that are performed within the respective S-Series ILS Specification SCs and WGs so as to harmonize and consolidate data requirements into one coherent data model.
Publication of SX000i, and continuing DMEWG coordination activities, enable the achievement of the vision for the suite of ILS specifications "to apply common logistics processes so as to share and exchange data securely through the life of products and services".
The companies and organizations that are currently participating in the development of SX000i are:
SX000i issue 1.0 was published in December 2015. An Issue 1.1 was published in July 2016.
The SX000i Steering Committee is currently co-chaired by the Spanish representative of Airbus Defence and Space , on behalf of ASD, and Boeing , on behalf of AIA.
SX000i is intended:
In that context, SX000i was developed for three primary applications:
The target audiences for SX000i are:
SX000i can be used by prime contractors, original equipment manufacturers, and suppliers as a reference for initially establishing their Product support strategies and plans, and selecting specifications to support those plans. SX000i can also be used to evaluate existing Product support strategies and projects.
SX000i can be used by customers to determine support requirements for new Products they are acquiring, or fielded Products for which they are seeking support, and to identify ILS specifications to be cited in solicitations.
The ILS specifications Council uses SX000i to promote a commonality and interoperability among the S-Series ILS specifications.
Steering committees and working groups developing specifications use SX000i as a basis for describing relationships and interfaces between the ILS element(s) that their specification covers and:
Steering committees use SX000i to ensure the compatibility of their specification with the other ILS specifications.
The Data modeling and Exchange Working group (DMEWG) uses SX000i to harmonize and consolidate data requirements into one coherent data model supporting all of the ILS specifications.
Steering committees and working groups both use SX000i to ensure compliance with ILS specification Council governance requirements.
SX000i consists of six chapters:
SX000i can be downloaded for free from its project website
The references below cover the specifications associated to the Integrated logistics support process described in SX000i, known as the ASD/AIA S-Series of ILS specifications : | https://en.wikipedia.org/wiki/SX000i |
The SYBYL line notation or SLN is a specification for unambiguously describing the structure of chemical molecules using short ASCII strings . SLN differs from SMILES in several significant ways. SLN can specify molecules, molecular queries, and reactions in a single line notation whereas SMILES handles these through language extensions. SLN has support for relative stereochemistry , it can distinguish mixtures of enantiomers from pure molecules with pure but unresolved stereochemistry. In SMILES aromaticity is considered to be a property of both atoms and bonds whereas in SLN it is a property of bonds.
Like SMILES, SLN is a linear language that describes molecules. This provides a lot of similarities with SMILES despite SLN's many differences from SMILES, and as a result, this description will heavily compare SLN to SMILES and its extensions.
Attributes, bracketed strings with additional data like [key1=value1, key2...] , is a core feature of SLN. Attributes can be applied to atoms and bonds. Attributes not defined officially are available to users for private extensions.
When searching for molecules, comparison operators such as fcharge>-0.125 can be used in place of the usual equal sign. A ! preceding a key/value group inverts the result of the comparison.
Entire molecules or reactions can too have attributes. The square brackets are changed to a pair of <> signs.
Anything that starts with an uppercase letter identifies an atom in SLN. Hydrogens are not automatically added, but the single bonds with hydrogen can be abbreviated for organic compounds, resulting in CH4 instead of C(H)(H)(H)H for methane . The author argues that explicit hydrogens allow for more robust parsing.
Attributes defined for atoms include I= for isotope mass number, charge= for formal charge, fcharge for partial charge, s= for stereochemistry, and spin= for radicals ( s , d , t respectively for singlet , doublet , triplet ). A formal charge of charge=2 can be abbreviated as +2 , and vice versa for negative charges; - and + is additionally recognized as −1 or +1 charges. * is a shorthand for spin=d . Stereochemistry on atoms is mostly tetrahedral, with the R / S and D / L available among others; it can be explicit ( E ) or relative ( R ), or specify a mixture ( M ) of stereoisomers at this atom. A normal/inverted ( N / I ) notation, equivalent to @@ and @ in SMILES, is provided. A lot of additional attributes are provided for searching.
In addition to elemental atoms SLN supports the specification of wild card atoms: Any (match any atom), and Hev (match any heavy atom). It also has an extensive Markush syntax for specifying combinatorial libraries and RGROUP queries. SLN has several query atom types for matching groups of atoms. Each type has the group name, followed by an optional positive integer.
The " 0 " mass number denotes the usual isotope, so N[I=0] equals N[I=14] matching 14 N and N[!I=0] matching every other isotope.
SLN uses largely the same bonding notation as SMILES, with - , = , # , and : for single, double, triple, and aromatic bonds. . is used for zero-order bonds, similarly to reaction SMILES, although a + is preferred for distinct molecules.
Most single bonds are implicit, so CH3CH3 (CH 3 CH 3 ) can be used instead of CH3-CH3 (CH 3 –CH 3 ) for ethane . Explicit single bonds are useful for three-center bonds.
The s= attribute is defined for double bonds, to convey stereochemistry information in E – Z ( E / Z ) or cis – trans ( c / t ) notation. N / I is available and stands for the "main" chain, which is trans or cis to each other.
SLN writes rings in a more explicit pattern than SMILES, with benzene specified as C[1]H:CH:CH:CH:CH:CH:@1 . An atom is tagged as an anchor on the ring with a single numeric attribute, and @1 can then be used to specify this (in our case, "number one") atom for bonding back to.
SLN branches are identical to SMILES branches, with parentheses specifying them. Propionic acid is CH3CH2C(=O)OH ( CH 3 CH 2 C ( = O ) OH {\displaystyle {\ce {\scriptstyle CH3CH2C(=O)OH}}} ).
SLN supports reactions with -> connecting the reactants and the products. Atom mapping is possible with the use of [# num ] attributes. The reaction center (rc) attribute can be added to bonds, and the chiral conversion (cc) attribute to atoms.
Multiple lines can be merged into a syntactical line by writing a \ (backslash) at the end of each line. This allows for breaking a long line into multiple lines, for example in a reaction with each molecule on its own line. | https://en.wikipedia.org/wiki/SYBYL_line_notation |
The SYZ conjecture is an attempt to understand the mirror symmetry conjecture, an issue in theoretical physics and mathematics. The original conjecture was proposed in a paper by Strominger , Yau , and Zaslow , entitled "Mirror Symmetry is T -duality". [ 1 ]
Along with the homological mirror symmetry conjecture , it is one of the most explored tools applied to understand mirror symmetry in mathematical terms. While the homological mirror symmetry is based on homological algebra , the SYZ conjecture is a geometrical realization of mirror symmetry.
In string theory , mirror symmetry relates type IIA and type IIB theories. It predicts that the effective field theory of type IIA and type IIB should be the same if the two theories are compactified on mirror pair manifolds.
The SYZ conjecture uses this fact to realize mirror symmetry. It starts from considering BPS states of type IIA theories compactified on X , especially 0-branes that have moduli space X . It is known that all of the BPS states of type IIB theories compactified on Y are 3-branes . Therefore, mirror symmetry will map 0-branes of type IIA theories into a subset of 3-branes of type IIB theories.
By considering supersymmetric conditions, it has been shown that these 3-branes should be special Lagrangian submanifolds . [ 2 ] [ 3 ] On the other hand, T-duality does the same transformation in this case, thus "mirror symmetry is T-duality".
The initial proposal of the SYZ conjecture by Strominger, Yau, and Zaslow, was not given as a precise mathematical statement. [ 1 ] One part of the mathematical resolution of the SYZ conjecture is to, in some sense, correctly formulate the statement of the conjecture itself. There is no agreed upon precise statement of the conjecture within the mathematical literature, but there is a general statement that is expected to be close to the correct formulation of the conjecture, which is presented here. [ 4 ] [ 5 ] This statement emphasizes the topological picture of mirror symmetry, but does not precisely characterise the relationship between the complex and symplectic structures of the mirror pairs, or make reference to the associated Riemannian metrics involved.
SYZ Conjecture: Every 6-dimensional Calabi–Yau manifold X {\displaystyle X} has a mirror 6-dimensional Calabi–Yau manifold X ^ {\displaystyle {\hat {X}}} such that there are continuous surjections f : X → B {\displaystyle f:X\to B} , f ^ : X ^ → B {\displaystyle {\hat {f}}:{\hat {X}}\to B} to a compact topological manifold B {\displaystyle B} of dimension 3, such that
The situation in which B reg = B {\displaystyle B_{\text{reg}}=B} so that there is no singular locus is called the semi-flat limit of the SYZ conjecture, and is often used as a model situation to describe torus fibrations. The SYZ conjecture can be shown to hold in some simple cases of semi-flat limits, for example given by Abelian varieties and K3 surfaces which are fibred by elliptic curves .
It is expected that the correct formulation of the SYZ conjecture will differ somewhat from the statement above. For example the possible behaviour of the singular set B ∖ B reg {\displaystyle B\backslash B_{\text{reg}}} is not well understood, and this set could be quite large in comparison to B {\displaystyle B} . Mirror symmetry is also often phrased in terms of degenerating families of Calabi–Yau manifolds instead of for a single Calabi–Yau, and one might expect the SYZ conjecture to reformulated more precisely in this language. [ 4 ]
The SYZ mirror symmetry conjecture is one possible refinement of the original mirror symmetry conjecture relating Hodge numbers of mirror Calabi–Yau manifolds. The other is Kontsevich's homological mirror symmetry conjecture (HMS conjecture). These two conjectures encode the predictions of mirror symmetry in different ways: homological mirror symmetry in an algebraic way, and the SYZ conjecture in a geometric way. [ 6 ]
There should be a relationship between these three interpretations of mirror symmetry, but it is not yet known whether they should be equivalent or one proposal is stronger than the other. Progress has been made toward showing under certain assumptions that homological mirror symmetry implies Hodge theoretic mirror symmetry. [ 7 ]
Nevertheless, in simple settings there are clear ways of relating the SYZ and HMS conjectures. The key feature of HMS is that the conjecture relates objects (either submanifolds or sheaves) on mirror geometric spaces, so the required input to try to understand or prove the HMS conjecture includes a mirror pair of geometric spaces. The SYZ conjecture predicts how these mirror pairs should arise, and so whenever an SYZ mirror pair is found, it is a good candidate to try and prove the HMS conjecture on this pair.
To relate the SYZ and HMS conjectures, it is convenient to work in the semi-flat limit. The important geometric feature of a pair of Lagrangian torus fibrations X , X ^ → B {\displaystyle X,{\hat {X}}\to B} which encodes mirror symmetry is the dual torus fibres of the fibration. Given a Lagrangian torus T ⊂ X {\displaystyle T\subset X} , the dual torus is given by the Jacobian variety of T {\displaystyle T} , denoted T ^ = J a c ( T ) {\displaystyle {\hat {T}}=\mathrm {Jac} (T)} . This is again a torus of the same dimension, and the duality is encoded in the fact that J a c ( J a c ( T ) ) = T {\displaystyle \mathrm {Jac} (\mathrm {Jac} (T))=T} so T {\displaystyle T} and T ^ {\displaystyle {\hat {T}}} are indeed dual under this construction. The Jacobian variety T ^ {\displaystyle {\hat {T}}} has the important interpretation as the moduli space of line bundles on T {\displaystyle T} .
This duality and the interpretation of the dual torus as a moduli space of sheaves on the original torus is what allows one to interchange the data of submanifolds and subsheaves. There are two simple examples of this phenomenon:
These two examples produce the most extreme kinds of coherent sheaf , locally free sheaves (of rank 1) and torsion sheaves supported on points. By more careful construction one can build up more complicated examples of coherent sheaves, analogous to building a coherent sheaf using the torsion filtration . As a simple example, a Lagrangian multisection (a union of k Lagrangian sections) should be mirror dual to a rank k vector bundle on the mirror manifold, but one must take care to account for instanton corrections by counting holomorphic discs which are bounded by the multisection, in the sense of Gromov-Witten theory . In this way enumerative geometry becomes important for understanding how mirror symmetry interchanges dual objects.
By combining the geometry of mirror fibrations in the SYZ conjecture with a detailed understanding of enumerative invariants and the structure of the singular set of the base B {\displaystyle B} , it is possible to use the geometry of the fibration to build the isomorphism of categories from the Lagrangian submanifolds of X {\displaystyle X} to the coherent sheaves of X ^ {\displaystyle {\hat {X}}} , the map F u k ( X ) → D b C o h ( X ^ ) {\displaystyle \mathrm {Fuk} (X)\to \mathrm {D} ^{b}\mathrm {Coh} ({\hat {X}})} . By repeating this same discussion in reverse using the duality of the torus fibrations, one similarly can understand coherent sheaves on X {\displaystyle X} in terms of Lagrangian submanifolds of X ^ {\displaystyle {\hat {X}}} , and hope to get a complete understanding of how the HMS conjecture relates to the SYZ conjecture.
This string theory -related article is a stub . You can help Wikipedia by expanding it .
This applied mathematics –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/SYZ_conjecture |
S is an axiomatic set theory set out by George Boolos in his 1989 article, "Iteration Again". S , a first-order theory, is two-sorted because its ontology includes "stages" as well as sets . Boolos designed S to embody his understanding of the "iterative conception of set" and the associated iterative hierarchy . S has the important property that all axioms of Zermelo set theory Z , except the axiom of extensionality and the axiom of choice , are theorems of S or a slight modification thereof.
Any grouping together of mathematical , abstract , or concrete objects, however formed, is a collection , a synonym for what other set theories refer to as a class . The things that make up a collection are called elements or members. A common instance of a collection is the domain of discourse of a first-order theory .
All sets are collections, but there are collections that are not sets. A synonym for collections that are not sets is proper class . An essential task of axiomatic set theory is to distinguish sets from proper classes, if only because mathematics is grounded in sets, with proper classes relegated to a purely descriptive role.
The Von Neumann universe implements the "iterative conception of set" by stratifying the universe of sets into a series of "stages", with the sets at a given stage being possible members of the sets formed at all higher stages. The notion of stage goes as follows. Each stage is assigned an ordinal number . The lowest stage, stage 0, consists of all entities having no members. We assume that the only entity at stage 0 is the empty set , although this stage would include any urelements we would choose to admit. Stage n , n >0, consists of all possible sets formed from elements to be found in any stage whose number is less than n . Every set formed at stage n can also be formed at every stage greater than n . [ 1 ]
Hence the stages form a nested and well-ordered sequence, and would form a hierarchy if set membership were transitive . The iterative conception has gradually become more accepted, despite an imperfect understanding of its historical origins.
The iterative conception of set steers clear, in a well-motivated way, of the well-known paradoxes of Russell , Burali-Forti , and Cantor . These paradoxes all result from the unrestricted use of the principle of comprehension of naive set theory . Collections such as "the class of all sets" or "the class of all ordinals " include sets from all stages of the iterative hierarchy. Hence such collections cannot be formed at any given stage, and thus cannot be sets.
This section follows Boolos (1998: 91). The variables x and y range over sets, while r , s , and t range over stages. There are three primitive two-place predicates :
The axioms below include a defined two-place set-stage predicate, Bxr , which abbreviates:
∃ s [ s < r ∧ F x s ] . {\displaystyle \exists s[s<r\land Fxs].}
Bxr is read as "set x is formed before stage r ".
Identity , denoted by infix '=', does not play the role in S it plays in other set theories, and Boolos does not make fully explicit whether the background logic includes identity. S has no axiom of extensionality and identity is absent from the other S axioms. Identity does appear in the axiom schema distinguishing S+ from S , [ 2 ] and in the derivation in S of the pairing , null set , and infinity axioms of Z . [ 3 ]
The symbolic axioms shown below are from Boolos (1998: 91), and govern how sets and stages behave and interact. The natural language versions of the axioms are intended to aid the intuition.
The axioms come in two groups of three. The first group consists of axioms pertaining solely to stages and the stage-stage relation ‘<’.
Tra : ∀ r ∀ s ∀ t [ r < s ∧ s < t → r < t ] . {\displaystyle \forall r\forall s\forall t[r<s\land s<t\rightarrow r<t]\,.}
"Earlier than" is transitive.
Net : ∀ s ∀ t ∃ r [ t < r ∧ s < r ] . {\displaystyle \forall s\forall t\exists r[t<r\land s<r]\,.}
A consequence of Net is that every stage is earlier than some stage.
Inf : ∃ r ∃ u [ u < r ∧ ∀ t [ t < r → ∃ s [ t < s ∧ s < r ] ] ] . {\displaystyle \exists r\exists u[u<r\land \forall t[t<r\rightarrow \exists s[t<s\land s<r]]]\,.}
The sole purpose of Inf is to enable deriving in S the axiom of infinity of other set theories.
The second and final group of axioms involve both sets and stages, and the predicates other than '<':
All : ∀ x ∃ r F x r . {\displaystyle \forall x\exists rFxr\,.}
Every set is formed at some stage in the hierarchy.
When : ∀ r ∀ x [ F x r ↔ [ ∀ y ( y ∈ x → B y r ) ∧ ¬ B x r ] ] . {\displaystyle \forall r\forall x[Fxr\leftrightarrow [\forall y(y\in x\rightarrow Byr)\land \lnot Bxr]]\,.}
A set is formed at some stage if and only if its members are formed at earlier stages.
Let A ( y ) be a formula of S where y is free but x is not. Then the following axiom schema holds:
Spec : ∃ r ∀ y [ A ( y ) → B y r ] → ∃ x ∀ y [ y ∈ x ↔ A ( y ) ] . {\displaystyle \exists r\forall y[A(y)\rightarrow Byr]\rightarrow \exists x\forall y[y\in x\leftrightarrow A(y)]\,.}
If there exists a stage r such that all sets satisfying A ( y ) are formed at a stage earlier than r , then there exists a set x whose members are just those sets satisfying A ( y ). The role of Spec in S is analogous to that of the axiom schema of specification of Z .
Boolos’s name for Zermelo set theory minus extensionality was Z- . Boolos derived in S all axioms of Z- except the axiom of choice . [ 4 ] The purpose of this exercise was to show how most of conventional set theory can be derived from the iterative conception of set, assumed embodied in S . Extensionality does not follow from the iterative conception, and so is not a theorem of S . However, S + Extensionality is free of contradiction if S is free of contradiction.
Boolos then altered Spec to obtain a variant of S he called S+ , such that the axiom schema of replacement is derivable in S+ + Extensionality. Hence S+ + Extensionality has the power of ZF . Boolos also argued that the axiom of choice does not follow from the iterative conception, but did not address whether Choice could be added to S in some way. [ 5 ] Hence S+ + Extensionality cannot prove those theorems of the conventional set theory ZFC whose proofs require Choice.
Inf guarantees the existence of stages ω, and of ω + n for finite n , but not of stage ω + ω. Nevertheless, S yields enough of Cantor's paradise to ground almost all of contemporary mathematics. [ 6 ]
Boolos compares S at some length to a variant of the system of Frege ’s Grundgesetze , in which Hume's principle , taken as an axiom, replaces Frege’s Basic Law V, an unrestricted comprehension axiom which made Frege's system inconsistent; see Russell's paradox . | https://en.wikipedia.org/wiki/S_(set_theory) |
S-phase index ( SPI ), is a measure of cell growth and viability , especially the capacity of tumor cells to proliferate. [ 1 ] It is defined as the number of BrdU -incorporating cells relative to the volume of DNA staining determined from whole mount confocal analyses.
Only cells in the S phase will incorporate BrdU into their DNA structure, which assists in determining length of the cell cycle .
This cell biology article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/S_phase_index |
In chemistry , the Sabatier principle is a qualitative concept in heterogeneous catalysis named after the French chemist Paul Sabatier . It states that the interactions between the catalyst and the reactants should be "just right"; that is, neither too strong nor too weak. If the interaction is too weak, the molecule will fail to bind to the catalyst and no reaction will take place. On the other hand, if the interaction is too strong, the product fails to dissociate . [ 1 ]
The principle can be shown graphically by plotting the reaction rate against a property such as the heat of adsorption of the reactant by the catalyst. Such plots pass through a maximum, looking roughly like a triangle or an inverted parabola , and are called volcano plots because of their shape. [ 1 ] Analogous three-dimensional plots can also be built against two different properties, such as the heats of adsorption of the two reactants for a two-component reaction. In that case the plot is generally shown as a contour plot and is called a volcano surface . [ 2 ] Volcano plots were introduced by Balandin. [ 3 ] [ 4 ]
The figure on the right shows a volcano plot for the decomposition of formic acid using different transition metals as catalysts. [ 5 ] In this case, the heat of formation ( Δ f H ) of the metal formate salt was used for the x axis because studies showed that the reaction intermediate was a surface formate. For the y axis, the temperature at which the reaction reaches a specific rate was used (the y axis is plotted in reverse to preserve the conventional "volcano" shape). At low values of Δ f H , the reaction is slow (in other words, requires higher temperatures) because the rate of adsorption is slow and rate-limiting . At high values of Δ f H , desorption becomes the rate-limiting step. The maximum rate, which is observed for the platinum group metals in this case, requires intermediate values of Δ f H , with the rate being a combination of the rate of adsorption and the rate of desorption. [ 3 ] Catalysts can exceed the Sabatier limit via catalytic resonance . | https://en.wikipedia.org/wiki/Sabatier_principle |
The Sabatier reaction or Sabatier process produces methane and water from a reaction of hydrogen with carbon dioxide at elevated temperatures (optimally 300–400 °C) and pressures (perhaps 3 megapascals (440 psi; 30 bar) [ 1 ] ) in the presence of a nickel catalyst . It was discovered by the French chemists Paul Sabatier and Jean-Baptiste Senderens in 1897. Optionally, ruthenium on alumina (aluminium oxide) makes a more efficient catalyst. It is described by the following exothermic reaction : [ 2 ]
There is disagreement on whether the CO 2 methanation occurs by first associatively adsorbing an adatom hydrogen and forming oxygen intermediates before hydrogenation or dissociating and forming a carbonyl before being hydrogenated. [ 3 ]
CO methanation is believed to occur through a dissociative mechanism where the carbon oxygen bond is broken before hydrogenation with an associative mechanism only being observed at high H 2 concentrations.
Methanation reactions over different metal catalysts including Ni, [ 4 ] Ru [ 5 ] and Rh [ 6 ] have been widely investigated for the production of CH 4 from syngas and other power to gas initiatives. [ 3 ] Nickel is the most widely used catalyst owing to its high selectivity and low cost. [ 2 ]
Methanation is an important step in the creation of synthetic or substitute natural gas (SNG). [ 7 ] Coal or wood undergo gasification which creates a producer gas that must undergo methaneation in order to produce a usable gas that just needs to undergo a final purification step.
The first commercial synthetic gas plant opened in 1984 and is the Great Plains Synfuels plant in Beulah, North Dakota. [ 2 ] As of 2016, it is still operational and produces 1500 MW worth of SNG using coal as the carbon source. In the years since its opening, other commercial facilities have been opened using other carbon sources such as wood chips. [ 2 ]
In France, AFUL Chantrerie, located in Nantes , in November 2017 opened the demonstrator MINERVE. The plant feeds a compressed natural gas station and sometimes injects methane into a natural gas fired boiler. [ 8 ]
The Sabatier reaction has been used in renewable-energy-dominated energy systems to use the excess electricity generated by wind, solar photovoltaic, hydro, marine current, etc. to make methane from hydrogen sourced from water electrolysis. [ 9 ] [ 10 ] In contrast to a direct usage of hydrogen for transport or energy storage applications, [ 11 ] the methane can be injected into the existing gas network. [ 12 ] [ 13 ] [ 14 ] The methane can be used on-demand to generate electricity overcoming low points of renewable energy production. The process is electrolysis of water by electricity to create hydrogen (which can partly be used directly in fuel cells) and the addition of carbon dioxide CO 2 (Sabatier reaction) to create methane. The CO 2 can be extracted from the air or fossil fuel waste gases by the amine process .
A 6 MW power-to-gas plant went into production in Germany in 2013, and powered a fleet of 1,500 Audi A3 . [ 15 ]
In ammonia production CO and CO 2 are considered poisons to most commonly used catalysts. [ 16 ] Methanation catalysts are added after several hydrogen producing steps to prevent carbon oxide buildup in the ammonia synthesis loop as methane does not have similar adverse effects on ammonia synthesis rates.
Oxygen generators on board the International Space Station produce oxygen from water using electrolysis ; the hydrogen produced was previously discarded into space. As astronauts consume oxygen, carbon dioxide is produced, which must then be removed from the air and discarded as well. This approach required copious amounts of water to be regularly transported to the space station for oxygen generation in addition to that used for human consumption, hygiene, and other uses—a luxury that will not be available to future long-duration missions beyond low Earth orbit .
NASA is using the Sabatier reaction to recover water from exhaled carbon dioxide and the hydrogen previously discarded from electrolysis on the International Space Station and possibly for future missions. [ 17 ] [ 18 ] The other resulting chemical, methane, is released into space. As half of the input hydrogen becomes wasted as methane, additional hydrogen is supplied from Earth to make up the difference. However, this creates a nearly-closed cycle between water, oxygen, and carbon dioxide which only requires a relatively modest amount of imported hydrogen to maintain.
The loop could be further closed if the waste methane was separated into its component parts by pyrolysis , the high efficiency (up to 95% conversion) of which can be achieved at 1200 °C: [ 19 ]
The released hydrogen would then be recycled back into the Sabatier reactor, leaving an easily removed deposit of pyrolytic graphite . The reactor would be little more than a steel pipe, and could be periodically serviced by an astronaut where the deposit is chiselled out. [ citation needed ]
Alternatively, the loop could be partially closed (75% of H 2 from CH 4 recovered) by incomplete pyrolysis of the waste methane while keeping the carbon locked up in gaseous form as acetylene : [ 20 ]
The Bosch reaction is also being investigated by NASA for this purpose, which is: [ 21 ]
The Bosch reaction would present a completely closed hydrogen and oxygen cycle which only produces atomic carbon as waste. However, difficulties maintaining its temperature of up to 600 °C and properly handling carbon deposits mean significantly more research will be required before a Bosch reactor could become a reality. One problem is that the production of elemental carbon tends to foul the catalyst's surface (coking), which is detrimental to the reaction's efficiency.
The Sabatier reaction has been proposed as a key step in reducing the cost of human mission to Mars ( Mars Direct , SpaceX Starship ) through in situ resource utilization . Hydrogen is combined with CO 2 from the atmosphere, with methane then stored as fuel and the water side product electrolyzed yielding oxygen to be liquefied and stored as oxidizer and hydrogen to be recycled back into the reactor. The original hydrogen could be transported from Earth or separated from Martian sources of water. [ 22 ] [ 23 ]
Importing a small amount of hydrogen avoids searching for water and just uses CO 2 from the atmosphere.
"A variation of the basic Sabatier methanation reaction may be used via a mixed catalyst bed and a reverse water gas shift in a single reactor to produce methane from the raw materials available on Mars, utilising carbon dioxide in the Martian atmosphere. A 2011 prototype test operation that harvested CO 2 from a simulated Martian atmosphere and reacted it with H 2 , produced methane rocket propellant at a rate of 1 kg/day, operating autonomously for 5 consecutive days, maintaining a nearly 100% conversion rate. An optimised system of this design massing 50 kg "is projected to produce 1 kg/day of O 2 :CH 4 propellant ... with a methane purity of 98+% while consuming ~17 kWh per day of electrical power (at a continuous power of 700 W). Overall unit conversion rate expected from the optimised system is one tonne of propellant per 17 MWh energy input. [ 24 ] "
The stoichiometric ratio of oxidiser and fuel is 2:1, for an oxygen/methane engine:
However, one pass through the Sabatier reactor produces a ratio of only 1:1. More oxygen may be produced by running the water-gas shift reaction (WGSR) in reverse (RWGS), effectively extracting oxygen from the atmosphere by reducing carbon dioxide to carbon monoxide .
Another option is to make more methane than needed and pyrolyze the excess of it into carbon and hydrogen (see above section), where the hydrogen is recycled back into the reactor to produce further methane and water. In an automated system, the carbon deposit may be removed by blasting with hot Martian CO 2 , oxidizing the carbon into carbon monoxide (via the Boudouard reaction ), which is vented. [ 25 ]
A fourth solution to the stoichiometry problem would be to combine the Sabatier reaction with the reverse water-gas shift (RWGS) reaction in a single reactor as follows: [ citation needed ]
This reaction is slightly exothermic, and when the water is electrolyzed, an oxygen to methane ratio of 2:1 is obtained.
Regardless of which method of oxygen fixation is utilized, the overall process can be summarized by the following equation: [ citation needed ]
Looking at molecular masses, 16 grams of methane and 64 grams of oxygen have been produced using 4 grams of hydrogen (which would have to be imported from Earth, unless Martian water was electrolysed), for a mass gain of 20:1; and the methane and oxygen are in the right stoichiometric ratio to be burned in a rocket engine. This kind of in situ resource utilization would result in massive weight and cost savings to any proposed crewed Mars or sample-return missions. | https://en.wikipedia.org/wiki/Sabatier_reaction |
Sabih Taher Darwish al-Masri is a Jordanian-Palestinian businessman. He is the founder and chairman of Arab Supply and Trading Company (Astra Group). He is also the chairman of Zara Investment Holding , Astra Industries, Paltel Corporation and Arab Bank , and a founder of the Palestine Securities Exchange (PSE). [ 1 ]
He is the cousin of Munib al-Masri . [ 2 ]
Al-Masri has a degree in chemical engineering from the University of Texas . [ 3 ]
Al-Masri co-founded Zara Investment Holding in 1994. | https://en.wikipedia.org/wiki/Sabih_al-Masri |
Saccharibacteria , formerly known as TM7 , [ 1 ] is a major bacterial lineage. It was discovered through 16S rRNA sequencing . [ 2 ]
TM7x from the human oral cavity was cultivated and revealed that TM7x is an extremely small coccus (200-300 nm) and has a distinctive lifestyle not previously observed in human-associated microbes. [ 3 ] It is an obligate epibiont of various hosts, including Actinomyces odontolyticus strain (XH001) yet also has a parasitic phase thereby killing its host. The full genome sequence revealed a highly reduced genome (705kB) [ 4 ] and a complete lack of amino acid biosynthetic capacity. An axenic culture of TM7 from the oral cavity was reported in 2014 but no sequence or culture was made available. [ 5 ]
Along with Candidate Phylum TM6 , [ 6 ] it was named after sequences obtained in 1994 in an environmental study of a soil sample of peat bog in Germany where 262 PCR amplified 16S rDNA fragments were cloned into a plasmid vector, named TM clones for Torf, Mittlere Schicht ( lit. peat, middle layer). [ 7 ] It has been found in several environments since such as from activated sludges , [ 8 ] [ 9 ] water treatment plant sludge [ 10 ] rainforest soil, [ 11 ] human saliva , [ 12 ] [ 13 ] in association with sponges , [ 14 ] cockroaches , [ 15 ] gold mines , [ 16 ] acetate -amended aquifer sediment, [ 17 ] and other environments (bar thermophilic ), making it an abundant and widespread phylum. Recently, TM7 rDNA and whole-cells were detected in activated sludge with >99.7% identity to a human skin TM7 and 98.6% identity to the human oral TM7a, [ 18 ] suggesting metabolically active TM7 isolates in environmental sites may serve as model organisms to investigate the role TM7 species play in human health.
TM7 specific FISH probes identified species from a bioreactor sludge revealed the presence of a gram-positive cell envelopes and several morphotypes : a sheathed filament (abundant), a rod occurring in short chains, a thick filament and cocci ; the former may be the cause of Eikelboom type 0041 (bulking problems of activated sludges). [ 10 ] The majority of bacterial phyla are Gram-negative diderms , whereas only the Bacillota , the Actinomycetota and Chloroflexota are monoderms . [ 19 ]
Using a polycarbonate membrane as a growth support and soil extract as the substrate, microcolonies of this clade were grown consisting of long filamentous rods up to 15 μm long with less than 50 cells or short rods with several hundred cells per colony, after 10 days incubation. [ 20 ]
Thanks to a microfluidic chip allowing the isolation and amplification of the genome of a single cell, the genome of 3 long filament morphology cells with identical 16S rRNA were sequenced to create a draft sequence of the genome confirming some previously ascertained properties, elucidating some of its metabolic capabilities, revealing novel genes and hinting to potential pathogenic abilities. [ 21 ]
Over 50 different phylotypes have been identified [ 19 ] and it has a relatively modest intradivision 16S rDNA sequence divergence of 17%, which ranges from 13 to 33%. [ 10 ] An interactive phylogenetic tree of TM7, [ 18 ] built using jsPhyloSVG , [ 22 ] allows for quick access to GenBank sequences and distance matrix calculations between tree branches.
Stable-isotope probing studies have found that some members of this phylum can degrade toluene . [ 23 ] [ 24 ]
" Ca. Chaera "
" Ca. Nanoperiodontomorbus "
" Ca. Nanogingivalis "
" Ca. Nanosyncoccus "
" Ca. Microsaccharimonas "
" Ca. Mycolatisynbacter "
" Ca. Saccharimonas "
" Ca. Nanosynbacter "
ABY1 ( OD1 -ABY1) [ 28 ]
Gracilibacteria (BD1-5 group)
Microgenomates (OP11 group)
Dojkabacteria (WS6)
Saccharibacteria (TM7)
SC3
WS5 [ 30 ] [ 31 ] [ 32 ]
Guaymas1 ( Thermodesulfobacteriota -related) [ 33 ]
Saccharibacteria I
Saccharibacteria II
Saccharibacteria IV
TM7a group
Saccharibacteria III
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) [ 34 ] and National Center for Biotechnology Information (NCBI) [ 1 ] | https://en.wikipedia.org/wiki/Saccharibacteria |
Saccharification is a term in biochemistry for denoting any chemical change wherein a monosaccharide molecule remains intact after becoming unbound from another saccharide. [ 1 ] For example, when a carbohydrate is broken into its component sugar molecules by hydrolysis (e.g., sucrose being broken down into glucose and fructose ). [ 2 ]
Enzymes such as amylases (e.g. in saliva ) and glycoside hydrolase (e.g. within the brush border of the small intestine ) are able to perform exact saccharification through enzymatic hydrolysis . [ 3 ] Through thermolysis , saccharification can also occur as a transient result, among many other possible effects, during caramelization . [ 4 ]
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Saccharification |
A saccharimeter is an instrument for measuring the concentration of sugar solutions.
This is commonly achieved using a measurement of refractive index ( refractometer ) or the angle of rotation of polarization of optically active sugars ( polarimeter ).
Saccharimeters are used in food processing industries, brewing , and the distilled alcoholic drinks industry. | https://en.wikipedia.org/wiki/Saccharimeter |
In absolute geometry , the Saccheri–Legendre theorem states that the sum of the angles in a triangle is at most 180°. [ 1 ] Absolute geometry is the geometry obtained from assuming all the axioms that lead to Euclidean geometry with the exception of the axiom that is equivalent to the parallel postulate of Euclid. [ a ]
The theorem is named after Giovanni Girolamo Saccheri and Adrien-Marie Legendre . It appeared in Saccheri's 1733 book Euclides ab omni naevo vindicatus [ Euclid Freed of Every Flaw ] but his work fell into obscurity. For many years after the theorem's rediscovery by Legendre it was called Legendre's theorem. [ 2 ]
The existence of at least one triangle with angle sum of 180 degrees in absolute geometry implies Euclid's parallel postulate. Similarly, the existence of at least one triangle with angle sum of less than 180 degrees implies the characteristic postulate of hyperbolic geometry . [ 3 ]
One proof of the Saccheri–Legendre theorem uses the Archimedean axiom , in the form that repeatedly halving one of two given angles will eventually produce an angle sharper than the second of the two. [ 1 ] Max Dehn gave an example of a non-Legendrian geometry where the angle sum of a triangle is greater than 180 degrees, and a semi-Euclidean geometry where there is a triangle with an angle sum of 180 degrees but Euclid's parallel postulate fails. In these Dehn planes the Archimedean axiom does not hold. [ 4 ]
This geometry-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Saccheri–Legendre_theorem |
Sacituzumab govitecan , sold under the brand name Trodelvy by Gilead Sciences , is a Trop-2 -directed antibody and topoisomerase inhibitor drug conjugate used for the treatment of metastatic triple-negative breast cancer and metastatic urothelial cancer. [ 8 ] [ 10 ] [ 11 ] [ 12 ]
The most common side effects include nausea , neutropenia , diarrhea , fatigue , anemia , vomiting , alopecia (hair loss), constipation , decreased appetite , rash and abdominal pain . [ 11 ] [ 12 ] [ 13 ] Sacituzumab govitecan has a boxed warning about the risk of severe neutropenia (abnormally low levels of white blood cells) and severe diarrhea. [ 11 ] [ 12 ] Sacituzumab govitecan may cause harm to a developing fetus or newborn baby. [ 11 ]
Sacituzumab govitecan was approved for medical use in the United States in April 2020, [ 11 ] [ 12 ] [ 14 ] and in the European Union in November 2021. [ 9 ] The U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA) consider it to be a first-in-class medication . [ 15 ] [ 16 ]
Sacituzumab govitecan is indicated for the treatment of adults with metastatic triple-negative breast cancer who received at least two prior therapies for metastatic disease; [ 10 ] people with unresectable locally advanced or metastatic triple-negative breast cancer (mTNBC) who have received two or more prior systemic therapies, at least one of them for metastatic disease; [ 13 ] and for people with locally advanced or metastatic urothelial cancer (mUC) who previously received a platinum-containing chemotherapy and either a programmed death receptor-1 (PD-1) or a programmed death-ligand 1 (PD-L1) inhibitor. [ 17 ]
It is also indicated for the treatment of people with unresectable locally advanced or metastatic hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative (IHC 0, IHC 1+ or IHC 2+/ISH-) breast cancer who have received endocrine-based therapy and at least two additional systemic therapies in the metastatic setting. [ 18 ]
Sacituzumab govitecan is a conjugate of the humanized anti- Trop-2 monoclonal antibody linked with SN-38 , the active metabolite of irinotecan . [ 19 ] Each antibody having on average 7.6 molecules of SN-38 attached. [ 20 ] Linkage to an antibody allows the drug to specifically target cells expressing Trop-2.
Sacituzumab govitecan is a Trop-2-directed antibody and topoisomerase inhibitor drug conjugate, meaning that the drug targets the Trop-2 receptor that helps the cancer grow, divide and spread, and is linked to topoisomerase inhibitor, which is a chemical compound that is toxic to cancer cells. [ 11 ] Approximately two of every ten breast cancer diagnoses worldwide are triple-negative. [ 11 ] Triple-negative breast cancer is a type of breast cancer that tests negative for estrogen receptors, progesterone receptors and human epidermal growth factor receptor 2 (HER2) protein. [ 11 ] Therefore, triple-negative breast cancer does not respond to hormonal therapy medicines or medicines that target HER2. [ 11 ]
Immunomedics announced in 2013, that it had received fast track designation from the US Food and Drug Administration (FDA) for the compound as a potential treatment for non-small cell lung cancer, small cell lung cancer, and metastatic triple-negative breast cancer. Orphan drug status was granted for small cell lung cancer and pancreatic cancer. [ 21 ] [ 22 ] In February 2016, Immunomedics announced that sacituzumab govitecan had received an FDA breakthrough therapy designation (a classification designed to expedite the development and review of drugs that are intended, alone or in combination with one or more other drugs, to treat a serious or life-threatening disease or condition) for the treatment of people with triple-negative breast cancer who have failed at least two other prior therapies for metastatic disease. [ 23 ] [ 24 ]
Sacituzumab govitecan was added to the proposed International nonproprietary name (INN) list in 2015, [ 25 ] and to the recommended list in 2016. [ 26 ]
Sacituzumab govitecan-hziy was approved for medical use in the United States in April 2020. [ 11 ] [ 12 ] [ 13 ] [ 27 ] [ 10 ]
Sacituzumab govitecan-hziy was approved based on the results of IMMU-132-01, a multicenter, single-arm clinical trial (NCT01631552) of 108 participants with metastatic triple-negative breast cancer who had received at least two prior treatments for metastatic disease. [ 11 ] [ 10 ] [ 12 ] Of the 108 participants involved within the study, 107 were female and 1 was male. [ 28 ] Participants received sacituzumab govitecan-hziy at a dose of 10 milligrams per kilogram of body weight intravenously on days one and eight every 21 days. [ 10 ] [ 28 ] Treatment with sacituzumab govitecan-hziy was continued until disease progression or unacceptable toxicity. [ 28 ] Tumor imaging was obtained every eight weeks. [ 10 ] [ 12 ] The efficacy of sacituzumab govitecan-hziy was based on the overall response rate (ORR) – which reflects the percentage of participants that had a certain amount of tumor shrinkage. [ 11 ] [ 10 ] The ORR was 33.3% (95% confidence interval [CI], 24.6 to 43.1). [ 11 ] [ 10 ] [ 28 ] Additionally, with the 33.3% of study participants who achieved a response, 2.8% of participants experienced complete responses. [ 28 ] The median time to response in participants was 2.0 months (range, 1.6 to 13.5), the median duration of response was 7.7 months (95% confidence interval [CI], 4.9 to 10.8), the median progression free survival was 5.5 months, and the median overall survival was 13.0 months. [ 28 ] Of the participants that achieved an objective response to sacituzumab govitecan-hziy, 55.6% maintained their response for six or more months and 16.7% maintained their response for twelve or more months. [ 11 ] [ 10 ]
Sacituzumab govitecan-hziy was granted accelerated approval along with priority review , breakthrough therapy , and fast track designations. [ 11 ] [ 10 ] [ 13 ] The U.S. Food and Drug Administration (FDA) granted approval of Trodelvy to Immunomedics, Inc. [ 11 ]
In April 2021, the FDA granted regular approval to sacituzumab govitecan for people with unresectable locally advanced or metastatic triple-negative breast cancer (mTNBC) who have received two or more prior systemic therapies, at least one of them for metastatic disease. [ 13 ] Efficacy and safety were evaluated in a multicenter, open-label, randomized trial (ASCENT; NCT02574455) conducted in 529 participants with unresectable locally advanced or mTNBC who had relapsed after at least two prior chemotherapies, one of which could be in the neoadjuvant or adjuvant setting, if progression occurred within twelve months. [ 13 ] Participants were randomized (1:1) to receive sacituzumab govitecan, 10 mg/kg as an intravenous infusion, on days 1 and 8 of a 21-day (n=267) cycle or physician's choice of single agent chemotherapy (n=262). [ 13 ]
In April 2021, the FDA granted accelerated approval to sacituzumab govitecan for people with locally advanced or metastatic urothelial cancer (mUC) who previously received a platinum-containing chemotherapy and either a programmed death receptor-1 (PD-1) or a programmed death-ligand 1 (PD-L1) inhibitor. [ 17 ] Efficacy and safety were evaluated in TROPHY (IMMU-132-06; NCT03547973), a single-arm, multicenter trial that enrolled 112 participants with locally advanced or mUC who received prior treatment with a platinum-containing chemotherapy and either a PD-1 or PD-L1 inhibitor. [ 17 ]
In February 2023, the FDA approved sacituzumab govitecan for people with unresectable locally advanced or metastatic hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative (IHC 0, IHC 1+ or IHC 2+/ISH-) breast cancer who have received endocrine-based therapy and at least two additional systemic therapies in the metastatic setting. [ 18 ] [ 29 ] [ 30 ]
On 14 October 2021, the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Trodelvy, intended for the treatment of unresectable or metastatic triple-negative breast cancer. [ 16 ] [ 31 ] The applicant for this medicinal product is Gilead Sciences Ireland UC. [ 31 ] Sacituzumab govitecan was approved for medical use in the European Union in November 2021. [ 9 ] [ 32 ] | https://en.wikipedia.org/wiki/Sacituzumab_govitecan |
A sacrificial metal is a metal used as a sacrificial anode in cathodic protection that corrodes to prevent a primary metal from corrosion or rusting . [ 1 ] It may also be used for galvanization.
When two metals touch each other and water is present, electrolysis occurs. [ 2 ] One well known example is the reaction between zinc (Zn) and iron (Fe). Zinc atoms will lose electrons in preference to the iron as they are more electropositive and therefore zinc is oxidized and corrodes.
Zn(s)→ Zn 2+ (aq) +2e (oxidation)
The capacity of a sacrificial metal may be calculated from first principle as follows:
By similar calculations Zinc and Magnesium have a capacity of 825 and 2206 Amp.Hours per Kg respectively.
Sacrificial metals are widely used to prevent other metals from corroding: for example in galvanised steel. [ 3 ] Many steel objects are coated with a layer of zinc, which is more electronegative than iron, and thus oxidises in preference to the iron, preventing the iron from rusting. [ 4 ] Similarly, sacrificial bars of a metal such as aluminium or aluminium alloys can be attached to an oil rig or to the hull of a ship to prevent it from rusting and breaking down. Magnesium may similarly be used on dry land for installations such as pipelines and oil refineries, where its high driving voltage is better for overcoming the resistance of soils found on dry land. [ 5 ] [ 6 ]
This electrochemistry -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Sacrificial_metal |
A sacrificial part is a part of a machine or product that is intentionally engineered to fail under excess mechanical stress , electrical stress , or other unexpected and dangerous situations. The sacrificial part is engineered to fail first, thus breaking the serial connection and protecting other parts of the system downstream. [ 1 ]
Examples of sacrificial parts include:
This article about a mechanical engineering topic is a stub . You can help Wikipedia by expanding it .
This technology-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Sacrificial_part |
The Saddam Line consisted of defensive fortifications constructed by Saddam Hussein 's Iraqi Army on Kuwait 's border with Saudi Arabia after Iraq had invaded and occupied Kuwait in August 1990.
The Western media presented fears that it would present a formidable obstacle to the liberation of Kuwait , consisting of "flame trenches" (ditches filled with oil to be ignited in case of attack) [ 1 ] [ 2 ] and "sand berms, trench works , anti-tank ditches , barbed wire and minefields ", [ 3 ] backed by the threat of chemical and biological weapons . The objective of Hussein was to force the coalition to engage in costly trench warfare . [ 4 ] However, those fears turned out to be unwarranted. The Coalition assault, beginning at 4 a.m. on February 24, 1991, met "only sporadic resistance", and by 6:45 a.m., troops had broken through the Saddam Line. [ 5 ] The US forces charged the Iraqi lines with M1 Abrams tanks modified with minesweeping plows and M728 Combat Engineer Vehicles which buried the trenchlines, and in many cases, buried Iraqi troops alive, the number of which has been estimated to be "in the thousands". [ 4 ] Though the Iraqi Government said they found 44 bodies. So it is unknown the true number.
Reference https://www.pbs.org/wgbh/pages/frontline/gulf/appendix/death.html
This Kuwait -related article is a stub . You can help Wikipedia by expanding it .
This article about the military of Iraq is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Saddam_Line |
In safe-life design , products are intended to be removed from service at a specific design life .
Safe-life is particularly relevant to simple metal aircraft, where airframe components are subjected to alternating loads over the lifetime of the aircraft which makes them susceptible to metal fatigue . In certain areas such as in wing or tail components, structural failure in flight would be catastrophic. [ 1 ]
The safe-life design technique is employed in critical systems which are either very difficult to repair or whose failure may cause severe damage to life and property. These systems are designed to work for years without requirement of any repairs.
The disadvantage of the safe-life design philosophy is that serious assumptions must be made regarding the alternating loads imposed on the aircraft, so if those assumptions prove to be inaccurate, cracks may commence prior to the component being removed from service. To counter this disadvantage, alternative design philosophies like fail-safe design and fault-tolerant design were developed.
One way the safe-life approach is planning and envisaging the toughness of the mechanisms in the automotive industry. When the repetitive loading on mechanical structures intensified with the advent of the steam engine, back in the mid-1800s, this approach was established (Oja 2013). According to Michael Oja, “Engineers and academics began to understand the effect that cyclic stress (or strain) has on the life of a component; a curve was developed relating the magnitude of the cyclic stress (S) to the logarithm of the number of cycles to failure (N)” (Oja 2013). The S-N curve because the fundamental relation is in safe life designs. The curve is reliant on many conditions, including the ratio of maximum load to minimum load (R-ratio), the type of material being inspected, and the regularity at which the cyclic stresses (or strains) are applied. Today, the curve is still consequential by experimentally testing laboratory specimens at many continuous cyclic load levels, and detecting the number of cycles to failure (Oja 2013). Michael Oja states that, “Unsurprisingly, as the load decreases, the life of the specimen increases” (Oja 2013). The practical limit of experimental challenges has been due to frequency confines of hydraulic-powered test machines. The load at which this high-cycle life happens has come to be recognized as the fatigue asset of the material (Oja 2013).
There are two generic types of aircraft structure, safe-life and fail-safe. The former is one that has low residual strength if a primary load-bearing member should fail, whereas the latter has alternative load paths so that if a primary load-bearing member cracks, residual strength remains because the loads can be assumed by adjacent members. In modern aircraft, fail-safe structures with up to three alternative load paths are provided, but back in 1947 the main load-bearing structure was safe life. This did not matter on an interim airframe designed for operations in the calm upper air, but at around 500 ft the loads and stresses were more volatile.
The safe-life design philosophy is applied to all helicopter structures. [ 2 ] In the current generation of Army helicopters, such as the UH-60 Black Hawk , composite materials make up as great as 17 percent of the airframe and rotor weight (Reddick). Harold Reddick states that, “With the advent of major helicopter composite structures R&D projects, such as the Advanced Composite Airframe Program (ACAP), and Manufacturing Methods and Technology (MM&T) projects, such as UH-60 Low Cost Composite Blade Program, it is estimated that within a few years composite materials could be applied to as much as 80% of the airframe and rotor weight of a helicopter in a production program” (Reddick). Along with this application, it is the essential obligation that sound, definitive design criteria be industrialized in order that the composite structures have high fatigue lives for economy of ownership and good damage tolerance for flight safety. Safe-life and damage-tolerant criteria are practical to all helicopter flight critical components (Reddick).
This communication design -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Safe-life_design |
The Safe Water System ( SWS ) is a series of inexpensive technologies that can be applied as water quality interventions in developing countries . [ 1 ] It was developed in conjunction by the US Centers for Disease Control and Prevention and the Pan American Health Organization . As of 2014, SWS had been implemented in thirty-five countries.
As of 2012, 780 million people lack access to an improved water source and 2.5 billion people (half of all people in developing countries) lack access to adequate sanitation . Inadequate water sanitation is a public health hazard, as it is a major source of diarrheal illnesses such as cholera . Diarrheal illnesses are a significant source of mortality for children, killing more children than the combined mortality of measles , malaria , and AIDS . For children under five, diarrheal disease is the second-leading cause of death worldwide. [ 2 ]
In 1992, the US Centers for Disease Control and Prevention (CDC) and the Pan American Health Organization collaborated to reduce waterborne diseases in developing countries. They called the new methodology the Safe Water System (SWS); it consisted of three components: [ 3 ]
From 1994 to 1995, the CDC implemented the SWS in Bolivia in a pilot experiment , where it improved water quality and reduced diarrheal illness by 40%. [ 4 ] Following the success of the program in Bolivia, the CDC received permission from the Zambian Ministry of Health to conduct field trials in 1998 in Kitwe , Zambia. Compared to the control group , the households that received the SWS and education on best hygiene practices experienced a 48% reduced risk of diarrheal disease. [ 3 ] In response to marketing efforts by the CDC, the sanitizing solution, sold as Clorin, experienced a steep increase in demand in Zambia. In 1999, about 187,000 bottles of Clorin were sold; in 2004, over 1.8 million bottles were sold. Each bottle sanitizes enough water for one month for a family of six. Clorin is subsidized by the United States Agency for International Development (USAID); as of 2003, each bottle is sold for US$0.09, with USAID paying $0.33 per bottle (each bottle therefore has a net cost of $0.24 to USAID). [ 5 ]
Household water treatment now encompasses other methods, such as use of flocculants that cause contaminants within water to sink to the bottom of a container or float at the top where they can be more easily removed. Methods like disinfectant powder, solar water disinfection , ceramic filtration , and slow sand filtration are also incorporated. [ 6 ]
From 1998 to 2014, the CDC implemented the SWS program in thirty-five countries. During this time period, they distributed enough sanitizing agents to clean over 137 billion liters of water. Products that the CDC has distributed as part of the Safe Water Systems includes the three-component system initially piloted in Bolivia, as well as water treatment tablets. SWS has been implemented in the following countries: [ 7 ]
Because the goal of the SWS interventions is to reduce the incidence of water-borne illness, SWS technologies do not mitigate other hazards in water such as chemical contaminants. [ 8 ] Studies of SWS interventions showed a reduction of diarrhea by 24% in Bangladesh, 25% in Guatemala, and 30% among people with HIV in rural Uganda. [ 9 ] | https://en.wikipedia.org/wiki/Safe_Water_System |
The Safe and Secure Innovation for Frontier Artificial Intelligence Models Act , or SB 1047 , was a failed [ 1 ] 2024 California bill intended to "mitigate the risk of catastrophic harms from AI models so advanced that they are not yet known to exist". [ 2 ] Specifically, the bill would have applied to models which cost more than $100 million to train and were trained using a quantity of computing power greater than 10 26 integer or floating-point operations. [ 3 ] SB 1047 would have applied to all AI companies doing business in California—the location of the company would not matter. [ 4 ] The bill would have created protections for whistleblowers [ 5 ] and required developers to perform risk assessments of their models prior to release, under the supervision of the Government Operations Agency . It would also have established CalCompute, a University of California public cloud computing cluster for startups, researchers and community groups.
The rapid increase in capabilities of AI systems in the 2020s, including the release of ChatGPT in November 2022, caused some researchers and members of the public to become concerned existential risks associated with increasingly powerful AI systems . [ 6 ] [ 7 ] For example, hundreds of tech executives and AI researchers signed a statement on AI in May 2023 that called for it to be a "global priority" similar to "pandemics and nuclear war." [ 8 ] However, the plausibility of this threat is still widely debated. [ 9 ]
Strong regulation of AI has been criticized for purportedly causing regulatory capture by large AI companies like OpenAI , a phenomenon in which regulation advances the interest of larger companies at the expense of smaller competition and the public in general. [ 7 ] Other advocates of AI regulation aim to prevent bias and privacy violations, rather than existential risks. [ 7 ] For example, some experts who view existential concerns as overblown and unrealistic view them as a distraction from near-term harms of AI like discriminatory automated decision making. [ 10 ]
In the face of existential concerns, technology companies have made voluntary commitments to conduct safety testing, for example at the AI Safety Summit and AI Seoul Summit . [ 11 ] [ 12 ]
In 2023, not long before the bill was proposed, Governor Newsom of California and President Biden issued executive orders on artificial intelligence. [ 13 ] [ 14 ] [ 15 ] State Senator Wiener said SB 1047 draws heavily on the Biden executive order , and is motivated by the absence of unified federal legislation on AI safety . [ 16 ] Historically, California has passed regulation on several tech issues itself, including consumer privacy and net neutrality , in the absence of action by Congress. [ 17 ] [ 18 ]
The bill was originally drafted by Dan Hendrycks , co-founder of the Center for AI Safety , who has previously argued that evolutionary pressures on AI could lead to "a pathway towards being supplanted as the Earth's dominant species." [ 19 ] [ 20 ] The center issued a statement in May 2023 co-signed by hundreds of AI researchers and business leaders stating that "Mitigating the risk of extinction from AI should be a global priority alongside other societal-scale risks such as pandemics and nuclear war." [ 21 ]
State Senator Wiener first proposed AI legislation for California through an intent bill called SB 294, the Safety in Artificial Intelligence Act, in September 2023. [ 22 ] [ 23 ] [ 24 ] On February 7, 2024, Wiener introduced SB 1047. [ 25 ] [ 26 ]
On May 21, SB 1047 passed the Senate 32-1. [ 27 ] [ 28 ] The bill was significantly amended by Wiener on August 15, 2024 in response to industry advice. [ 29 ] Amendments included adding clarifications, and removing the creation of a "Frontier Model Division" and the penalty of perjury . [ 30 ] [ 31 ]
On August 28, the bill passed the State Assembly 48-16. Then, due to the amendments, the bill was once again voted on by the Senate, passing 30-9. [ 32 ] [ 33 ]
On September 29, Governor Gavin Newsom vetoed the bill. [ 34 ] The deadline for California lawmakers to overrule Newsom's veto (30 November 2024) has now passed. [ 1 ]
Newsom cited concerns over the bill's regulatory framework targeting only large AI models based on their computational size, while not taking into account whether the models are deployed in high-risk environments. [ 35 ] [ 36 ] Newsom emphasized that this approach could create a false sense of security, overlooking smaller models that might present equally significant risks. [ 35 ] [ 37 ] He acknowledged the need for AI safety protocols [ 35 ] [ 38 ] but stressed the importance of adaptability in regulation as AI technology continues to evolve rapidly. [ 35 ] [ 39 ]
Governor Newsom also committed to working with technology experts, federal partners, and research institutions, including the Carnegie Endowment for International Peace , led by former California Supreme Court Justice Mariano-Florentino Cuéllar ; and Stanford University's Human-Centered AI (HAI) Institute , led by Dr. Fei-Fei Li . He announced plans to collaborate with these entities to advance responsible AI development, aiming to protect the public while fostering innovation. [ 35 ] [ 40 ]
SB 1047 would have covered AI models with training compute over 10 26 integer or floating-point operations and a cost of over $100 million. [ 3 ] [ 41 ] If a covered model is fine-tuned using more than $10 million, the resulting model would also have been covered. [ 31 ]
Developers of covered models and derivatives would have been required to submit a certification, subject to auditing, before training models. The certification would have shown mitigation of "reasonable" risk of "critical harms" of the covered model and its derivatives, including post-training modifications. Safeguards to reduce risk included the ability to shut down the model, [ 5 ] which has been variously described as a " kill switch " [ 42 ] and " circuit breaker ". [ 43 ] Whistleblowing provisions protect employees who report safety problems and incidents. [ 5 ]
The bill would have defined critical harms with respect to four categories: [ 2 ] [ 44 ]
Additionally, SB 1047 would have created a public cloud computing cluster called CalCompute, associated with the University of California , to support startups, researchers, and community groups that lack large-scale computing resources. [ 30 ]
SB 1047 would have required developers, beginning January 1, 2026, to annually retain a third-party auditor to perform an independent audit of compliance with the requirements of the bill, as provided. [ 30 ] The Government Operations Agency would have reviewed the results of safety tests and incidents, and issue guidance, standards, and best practices. [ 30 ] The bill would have created a Board of Frontier Models to supervise the application of the bill by the Government Operations Agency. It is would be composed of 9 members. [ 30 ]
Proponents of the bill described its provisions as simple and narrowly-focused, with Sen. Scott Weiner describing it as a "light-touch, basic safety bill". [ 46 ] This was disputed by critics of the bill, who described the bill's language as vague and criticized it as consolidating power in the largest AI companies at the expense of smaller ones. [ 46 ] Proponents, in turn, argued that the bill only applies to models trained using more than 10 26 FLOPS and with over $100 millions, or fine-tuned with more than $10 millions, and that the threshold could be increased if needed. [ 47 ]
The penalty of perjury was also a subject of debate, and was eventually removed through an amendment. The scope of the "kill switch" requirement was also reduced, following concerns from open-source developers. The use of the term "reasonable assurance" in the bill was also controversial, and it was eventually amended to "reasonable care". Critics then argued that "reasonable care" imposed an excessive burden by requiring confidence that models could not be used to cause catastrophic harm; proponents claimed that the standard did not require certainty and that it already applied to AI developers under existing law. [ 47 ]
Individual supporters of the bill included Turing Award recipients Yoshua Bengio [ 48 ] and Geoffrey Hinton , [ 49 ] Elon Musk , [ 50 ] Bill de Blasio , [ 51 ] Kevin Esvelt , [ 52 ] Dan Hendrycks , [ 53 ] Vitalik Buterin , [ 54 ] OpenAI whistleblowers Daniel Kokotajlo [ 45 ] and William Saunders, [ 55 ] Lawrence Lessig , [ 56 ] Sneha Revanur , [ 57 ] Stuart Russell , [ 56 ] Jan Leike , [ 58 ] actors Mark Ruffalo , Sean Astin , and Rosie Perez , [ 59 ] Scott Aaronson , [ 60 ] and Max Tegmark . [ 61 ] Over 120 Hollywood celebrities, including Mark Hamill , Jane Fonda , and J. J. Abrams , also signed a statement in support of the bill. [ 62 ] Max Tegmark likened the bill's focus on holding companies responsible for the harms caused by their models to the FDA requiring clinical trials before a company can release a drug to the market. [ 61 ]
Organizations sponsoring the bill included the Center for AI Safety , Economic Security California and Encode Justice. [ 63 ] The labor union SAG-AFTRA and two women's groups, the National Organization for Women and Fund Her , sent support letters to Governor Newsom. [ 64 ] The Los Angeles Times editorial board also wrote in support of the bill. [ 65 ]
Individual opponents of the bill included Andrew Ng , Fei-Fei Li , [ 66 ] Russell Wald, [ 67 ] Ion Stoica , Jeremy Howard , Turing Award recipient Yann LeCun , and U.S. Congressmembers Nancy Pelosi , Zoe Lofgren , Anna Eshoo , Ro Khanna , Scott Peters , Tony Cárdenas , Ami Bera , Nanette Barragán and Lou Correa . [ 7 ] [ 68 ] [ 69 ] Andrew Ng called for more targeted regulatory approaches, such as the targeting of deepfake pornography , the watermarking of generated materials, and investment in red teaming and other security measures. [ 70 ]
The University of California and Caltech researchers also wrote open letters in opposition. [ 68 ]
The bill was opposed by industry trade associations including the California Chamber of Commerce , the Chamber of Progress , [ a ] the Computer & Communications Industry Association [ b ] and TechNet. [ c ] [ 3 ] Companies including Meta [ 74 ] and OpenAI [ 75 ] were opposed to or raised concerns about the bill, while Google , [ 74 ] Microsoft and Anthropic [ 61 ] proposed substantial amendments. [ 4 ] However, Anthropic announced its support for an amended version of the bill while mentioning that some aspects of the bill which they said seemed concerning or ambiguous to them. [ 76 ] Several startup founder and venture capital organizations opposed to the bill, for example, Y Combinator , [ 77 ] [ 78 ] Andreessen Horowitz , [ 79 ] [ 80 ] [ 81 ] Context Fund [ 82 ] [ 83 ] and Alliance for the Future. [ 84 ]
After the bill was amended, Anthropic CEO Dario Amodei wrote that "the new SB 1047 is substantially improved, to the point where we believe its benefits likely outweigh its costs. However, we are not certain of this, and there are still some aspects of the bill which seem concerning or ambiguous to us." [ 85 ] xAI CEO Elon Musk also supported the bill. [ 86 ] On September 9, 2024, at least 113 current and former employees of AI companies OpenAI, Google DeepMind, Anthropic, Meta, and xAI signed a letter to Governor Newsom in support of SB 1047. [ 87 ] [ 88 ]
Critics expressed concerns about liability on open source software imposed by the bill if they use or improve existing freely available models. Yann LeCun , the Chief AI Officer of Meta , has suggested the bill would kill open source AI models. [ 70 ] There were concerns in the open-source community that due to the threat of legal liability companies like Meta may choose not to make models (for example, Llama ) freely available. [ 89 ] [ 90 ] The AI Alliance wrote in opposition to the bill, among other open-source organizations. [ 68 ] In contrast, Creative Commons co-founder Lawrence Lessig wrote that SB 1047 would make open source AI models safer and more popular with developers, since both harm and liability for that harm would be less likely. [ 43 ]
The Artificial Intelligence Policy Institute, a pro-regulation AI think tank, [ 91 ] [ 92 ] ran three polls of California respondents on whether they supported or opposed SB 1047. [ 93 ] [ 94 ] [ 95 ] [ 96 ] [ 97 ] [ 98 ] The third poll asked the question "Some policy makers are proposing a law in California, Senate Bill 1047, which would require that companies that develop advanced AI conduct safety tests and create liability for AI model developers if their models cause catastrophic harm and they did not take appropriate precautions." [ 99 ] The options were "Support", "Oppose", and "Not Sure". [ 93 ] [ 94 ] Their poll results were 53.8–64.2% support in July, [ 93 ] [ 94 ] 60.1–69.9% support in early August, [ 95 ] [ 96 ] and 65.8–74.2% support in late August. [ 97 ] [ 98 ]
On the other side of the aisle, the California Chamber of Commerce conducted its own poll, showing that 28 % of respondents supported the bill, 46 % opposed, and 26 % were neutral. The framing of the question has however been described as "badly biased". [ 92 ] The summary of the bill in their question was "Lawmakers in Sacramento have proposed a new state law—SB 1047—that would create a new California state regulatory agency to determine how AI models can be developed. This new law would require small startup companies to potentially pay tens of millions of dollars in fines if they don’t implement orders from state bureaucrats. Some say burdensome regulations like SB 1047 would potentially lead companies to move out of state or out of the country, taking investment and jobs away from California." [ 100 ]
A YouGov poll commissioned by the Economic Security Project , which co-sponsored the bill, found that 78% of registered voters across the United States supported SB 1047, and 80% thought that Governor Newsom should sign the bill. [ 101 ] Their question was "The California legislature passed a bill recently to regulate artificial intelligence, or AI, and since so many AI companies are based there, it could have national impacts.The bill would require California companies developing the next generation of most powerful AI systems to test for safety risks before releasing them. If testing shows that the AI system could be used to cause catastrophic harm to society, such as disrupting the financial system, shutting down the power grid, or creating biological weapons, the company must add reasonable safeguards to prevent these risks. If the company fails to test or adopt reasonable safeguards, they could be held accountable by the Attorney General of California." [ 101 ]
A David Binder Research poll commissioned by the Center for AI Safety , a group focused on mitigating societal-scale risk and a sponsor of the bill, found that 77% of Californians support a proposal to require companies to test AI models for safety risks, and 86% consider it an important priority for California to develop AI safety regulations. [ 102 ] [ 103 ] [ 104 ] [ 105 ] Their question was "The proposal would require California companies developing the next generation of most powerful AI systems to test for safety risks before releasing them. If testing shows that the AI system could be used to cause catastrophic harm to society, such as disrupting the financial system, shutting down the power grid or creating biological weapons, the company must add reasonable safeguards to prevent these risks. If the company fails to test or adopt reasonable safeguards, they could be held accountable by the Attorney General of California." [ 102 ] | https://en.wikipedia.org/wiki/Safe_and_Secure_Innovation_for_Frontier_Artificial_Intelligence_Models_Act |
The safe handling of carcinogens is the handling of cancer causing substances in a safe and responsible manner. Carcinogens are defined as 'a substance or agent that can cause cells to become cancerous by altering their genetic structure so that they multiply continuously and become malignant '. [ 1 ] The World Health Organization breaks down the three types of carcinogens that can cause cancer in humans. The first type of carcinogen is the physical type which can be ultraviolet and ionizing radiation. The second type of carcinogens is defined as asbestos , tobacco smoke, alcohol, aflatoxin , and arsenic . The third type of carcinogen is biological which highlights infections that can be caused from viruses, bacteria, or parasites. [ 2 ] There are many risk factors when it comes to the human body and carcinogens, which is why it is so important that the proper approach is used when attempting to reduce expose to cancer causing carcinogens.
The main routes of exposure to carcinogens come from direct contact through the methods of inhalation , contact, injection , absorption or ingestion . [ 3 ] Each of these exposure routes and severity of damage can vary depending on the potential carcinogen in question. As many carcinogens have a chronic effect and symptoms may only appear after repeated long term exposure, making symptoms and exposure hard to monitor.
The World Health Organization determines that approximately 30 to 50% of current known cancers can be prevented if the proper prevention methods are utilized. [ 3 ] Prevention can be brought about in different ways, with each having different effectiveness levels. Many employers have standard operating procedures that are in place to ensure carcinogens are handled properly with the correct level of protection for the individual handling the carcinogen. [ 4 ] Prevention can be accomplished by:
Standard containment devices such as fume hoods , glove boxes , use of high efficiency particulate air (HEPA) filters, ventilated containment or weighing, or placing the carcinogenic substance in a sealed weighed container (Tare Method). The employment of these methods and equipment can help reduce the unnecessary exposure to the carcinogens. Special care must be taken when using single exposure carcinogens such as polycyclic aromatic hydrocarbons . [ 5 ] All surfaces where carcinogens are used must be of a suitable material, e.g.: stainless steel, plastic trays or absorbent plastic backed paper. Correct signs must be placed outside of the work stating 'No eating, drinking or smoking' and 'Danger carcinogen in use. Authorized personnel only'. [ 6 ]
Ideally carcinogenic substances should be avoided by substitution with less hazardous substances. Alternate form of carcinogenic substances may also be used to minimize the risk of exposure. In the case of carcinogens which pose a danger through inhalation, pastes or pellets can be used to avoid the possibility of airborne dust. Volatile liquids can also potentially be substituted with paste forms to avoid excessive formation of vapors. [ 7 ]
The correct personal protective equipment must be worn when handling carcinogens. Ensure safety goggles , impermeable gloves (of an appropriate material), respirator (if appropriate), face shield , impermeable apron, closed toed shoes, long sleeved lab coat are worn. Disposable aprons and lab coats are preferable to reduce risks of repeated exposure. [ 8 ]
A quick response to an accident or spill can greatly reduce exposure to a carcinogenic substance. If a spill or accident occurs ensure that the contaminated materials are disposed of in the correct hazardous waste bin (ensure stained clothing is removed immediately), a correct spill kit is used on the spill, in the case of a liquid spill, ensure that the spill is cleaned as soon as possible to prevent the formation of aerosols , have employees tested for exposure to carcinogens, refer to MSDS for specific treatment or dangers. Prepare spill kits and emergency plans prior to beginning use of the carcinogenic substances and in the case of a large spill vacate the area and call for assistance. [ 4 ]
The correct storage of carcinogens is important in reducing exposure. Limit access to carcinogens, keep containers and amounts used as small as possible, double containers and chemical resistant trays. Store in a designated area with the appropriate hazard signs and ventilation if required. The carcinogens should be stored in a separate area to flammable solids and corrosive liquids as to avoid any damage to containers and possible leaking of carcinogenic compounds. Refer to the MSDS or the company specific standard operating procedures for the best solution to storing any carcinogen. [ 4 ]
After use of a carcinogen or if exposure to a carcinogen has occurred, ensure the correct decontamination procedure is executed. Personnel must wash hands and arms with soap and water , immediately after handling. If exposure occurs, contact emergency health services and use safety shower/eye wash station. Decontamination of area procedures vary depending on the material being handled. Toxicity of some materials can be neutralized with other agents (refer to the MSDS for appropriate action). All surfaces should be wiped down with an appropriate cleaning agent. All waste materials and contaminated PPE must be disposed of in hazardous waste bins. All equipment used must be decontaminated before removing them from the designated area. [ 4 ] [ 8 ] | https://en.wikipedia.org/wiki/Safe_handling_of_carcinogens |
Safe household water storage is a critical component of a Household Water Treatment and Safe Storage (HWTS) system being promoted by the World Health Organization (WHO) worldwide in areas that do not have piped drinking water. In these areas, it is not uncommon for drinking water to be stored in a pot, jar, crock or other container in the home. Even if this drinking water was of acceptable microbiological quality initially, it can become contaminated by dirty hands and utensils, such as dirty diapers and cups. Drinking water containers with "narrow dispensers are key" to keeping water from being contaminated while being stored in the home. [ 1 ]
All types of 'safe household water storage must be used with water from known clean sources or with water having received prior efficacious treatment. [ citation needed ]
The United Nations' Millennium Declaration adopted by its General Assembly in September 2000 set Millennium Development Goals (MDG) that have a purpose of significantly reducing the proportion of people in the world in extreme poverty. Resolution 19 specifically states with respect to drinking water, "To halve, by the year 2015...the proportion of the world's people who are unable to reach or to afford safe drinking water". [ 3 ] In 2009 the United Nations published The Millennium Development Goals Report that states: "The world is well on its way to meeting the drinking water target, though some countries still face enormous challenges." [ 4 ] One way that the World Health Organization (WHO) has supported the safe drinking water goal is with its Household Water Treatment and Safe Storage (HWTS) program which targets people who are not connected to community water systems. Their website states that improved HWTS techniques can dramatically improve drinking water quality and reduce diarrhoeal diseases for those who must rely on unsafe water supplies. It reminds us that there are 1.6 million diarrhoeal deaths per year related to unsafe water, sanitation, and hygiene and that these are mostly of children under 5 years old. [ 5 ] | https://en.wikipedia.org/wiki/Safe_household_water_storage |
For power semiconductor devices (such as BJT , MOSFET , thyristor or IGBT ), the safe operating area (SOA) is defined as the voltage and current conditions over which the device can be expected to operate without self-damage. [ 1 ]
SOA is usually presented in transistor datasheets as a graph with V CE (collector-emitter voltage) on the abscissa and I CE (collector-emitter current) on the ordinate ; the safe 'area' referring to the area under the curve. The SOA specification combines the various limitations of the device — maximum voltage, current, power, junction temperature , secondary breakdown — into one curve, allowing simplified design of protection circuitry.
Often, in addition to the continuous rating, separate SOA curves are also plotted for short duration pulse conditions (1 ms pulse, 10 ms pulse, etc.).
The safe operating area curve is a graphical representation of the power handling capability of the device under various conditions. The SOA curve takes into account the wire bond current carrying capability, transistor junction temperature, internal power dissipation and secondary breakdown limitations.
Where both current and voltage are plotted on logarithmic scales , the borders of the SOA are straight lines:
SOA specifications are useful to the design engineer working on power circuits such as amplifiers and power supplies as they allow quick assessment of the limits of device performance, the design of appropriate protection circuitry, or selection of a more capable device. SOA curves are also important in the design of foldback circuits.
For a device that makes use of the secondary breakdown effect see Avalanche transistor
Secondary breakdown is a failure mode in bipolar power transistors. In a power transistor with a large junction area, under certain conditions of current and voltage, the current concentrates in a small spot of the base-emitter junction. This causes local heating, progressing into a short between collector and emitter. This often leads to the destruction of the transistor. Secondary breakdown can occur both with forward and reverse base drive. [ 2 ] Except at low collector-emitter voltages, the secondary breakdown limit restricts the collector current more than the steady-state power dissipation of the device. [ 3 ] Older power MOSFETs did not exhibit secondary breakdown, with their safe operating area being limited only by maximum current (the capacity of the bonding wires), maximum power dissipation and maximum voltage. This has changed in more recent devices as detailed in the next section. [ 4 ] However, power MOSFETs have parasitic PN and BJT elements within the structure, which can cause more complex localized failure modes resembling secondary breakdown.
In their early history, MOSFETs became known for their absence of secondary breakdown. This benefit was due to the fact that ON-resistance increases with increasing temperature, so that part of the MOSFET which is running hotter (e.g. due to irregularities in the die-attachment, etc.) will carry a lower current density, tending to even out any temperature variation and prevent hot spots. Recently, MOSFETs with very high transconductance, optimised for switching operation, have become available. When operated in linear mode, especially at high drain-source voltages and low drain currents, the gate-source voltage tends to be very close to the threshold voltage. Unfortunately the threshold voltage decreases as temperature increases, so that if there are any slight temperature variations across the chip, then the hotter regions will tend to carry more current than the cooler regions when Vgs is very close to Vth. This can lead to thermal runaway and the destruction of the MOSFET even when it is operating within its Vds, Id and Pd ratings. [ 5 ] [ 6 ] Some (usually expensive) MOSFETs are specified for operation in the linear region and include DC SOA diagrams, e.g. IXYS IXTK8N150L. [ 7 ]
Transistors require some time to turn off, due to effects such as minority carrier storage time and capacitance. While turning off, they may be damaged depending on how the load responds (especially with poorly snubbed inductive loads). The reverse bias safe operating area (or RBSOA ) is the SOA during the brief time before turning the device into the off state—during the short time when the base current bias is reversed. As long as the collector voltage and collector current stay within the RBSOA during the entire turnoff, the transistor will be undamaged. Typically the RBSOA will be specified for a variety of turn-off conditions, such as shorting the base to the emitter, but also faster turn-off protocols where the base-emitter voltage bias is reversed.
The RBSOA shows distinct dependencies compared to the normal SOA. For example in IGBTs the high-current, high-voltage corner of the RBSOA is cut out when the collector voltage increases too quickly. [ 8 ] Since the RBSOA is associated with a very brief turn-off process, it is not constrained by the continuous power dissipation limit.
The ordinary safe operating area (when the device is in the on state) may be referred to as the Forward bias safe operating area (or FBSOA ) when it is possible to confuse it with the RBSOA.
The most common form of SOA protection used with bipolar junction transistors senses the collector-emitter current with a low-value series resistor. The voltage across this resistor is applied to a small auxiliary transistor that progressively 'steals' base current from the power device as it passes excess collector current.
Another style of protection is to measure the temperature of the outside of the transistor, as an estimate of junction temperature, and reduce drive to the device or switch it off if the temperature is too high. If multiple transistors are used in parallel, only a few need to be monitored for case temperature to protect all parallel devices.
This approach is effective but not bullet-proof. In practice, it is very difficult to design a protection circuit that will work under all conditions, and it is left up to the design engineer to weigh the likely fault conditions against the complexity and cost of the protection. | https://en.wikipedia.org/wiki/Safe_operating_area |
SafetyNET p is a standard for Ethernet -based fieldbus communication in automation technology . SafetyNET p is suitable as a drive bus due to its real-time behaviour , with cycle times of up to 62.5 μs. In accordance with the standard requirements from EN 61508 and EN 61511, it can be used in safety circuits up to and including Category 3, SIL 3.
SafetyNET p is a registered trademark of Pilz GmbH & Co. KG and was presented in public for the first time in 2006. Its objective was to enable fieldbus communication on Ethernet in real-time and to simultaneously provide data communication in terms of machinery safety . SafetyNET p combines safety and automation: it is both a safety and an automation fieldbus and as such is the successor to SafetyBUS p .
The SafetyNET p technology is managed through the umbrella organisation Safety Network International e.V.
In addition to its use as an Ethernet-based fieldbus, a key component in the application of SafetyNET p is the communication of data with a safety-related content. SafetyNET p can be used anywhere that communicated data has to be consistent in terms of time and content, in order to safeguard against danger. This danger may concern hazards to life and limb, but may also involve the protection of economic assets.
A second application area is the communication of data in real-time. With bus cycle times of up to 62,5 μs, [ 1 ] SafetyNET p can even be used in extremely time-critical areas.
Typical application areas are:
In general, all automation and process engineering applications are possible.
SafetyNET p is based on Ethernet. There are two different but compatible versions of SafetyNET p.
RTFN (Real time frame network) uses conventional Ethernet IP frames for communication. The mechanisms for security and real-time are located on OSI levels 3 and above. A producer-consumer model is used as the communication principle. A central process controller (PLC) is not required. This enables concepts such as modular engineering , for example.
SafetyNET p RTFN is fully compatible with all IP-based Ethernet protocols and can be combined on the same medium. Conventional switches, routers and wireless access points can also be used.
A system cycle time of around 1 ms can be achieved, depending on potential competing services. If higher performance is required, SafetyNET p RTFL can be used.
RTFL (Real time frame line) uses Ethernet MAC frames for communication. A producer-consumer model is also used at logical level on RTFL. In order to achieve the required performance, communication takes place in optimised Ethernet MAC frames. The first subscriber in the logical line sends an Ethernet MAC frame to its logical neighbour, which completes its part of the frame and then passes the frame along the logical line to its nearest neighbour. This way all subscribers fill in the frame in succession. The last subscriber in the line sends the completed frame back to the first subscriber using the same channel (via all the subscribers). In the process, individual subscribers can remove the data they need as the frame passes through.
System cycle times in the area of 62.5 μs can be achieved. SafetyNET p subscribers can pack miscellaneous IP-based traffic within an RTFL frame as part of real-time communication.
The SafetyNet p frame data, as determined by the technology, is as follows:
SafetyNET p is assigned port number 40000 on IANA ’s "List of assigned port numbers ".
The user organisation Safety Bus p Club International e.V. combines manufacturers and users of SafetyBUS p and has been in existence since 1999. In 2006 the organisation was renamed Safety Network International e.V. In addition to the international organisation there are also two other regional organisations: Japan was established in 2000, while the United States was established in 2001. | https://en.wikipedia.org/wiki/SafetyNET_p |
Safety Science is a monthly peer-reviewed scientific journal published by Elsevier covering research on all aspects of human and industrial safety . [ 1 ] The editor-in-chief is Georgios Boustras ( European University Cyprus ),. [ 2 ] The journal was established in 1976 as the Journal of Occupational Accidents , with Herbert Eisner as founding editor-in-chief. [ 3 ] In 1990, the aims and scope of the journal were expanded, and the journal obtained its current name. [ 4 ] [ 5 ]
Since 1990, the following persons are or have been editors-in-chief: [ 4 ]
The journal is abstracted and indexed in:
According to the Journal Citation Reports , the journal has a 2023 impact factor of 4.7. [ 14 ]
This article about a scientific journal is a stub . You can help Wikipedia by expanding it .
See tips for writing articles about academic journals . Further suggestions might be found on the article's talk page . | https://en.wikipedia.org/wiki/Safety_Science |
Safety engineers focus on development and maintenance of the integrated management system. They act as a quality assurance and conformance specialist.
Health and safety engineers are responsible for developing and maintaining the safe work systems for employees and others.
The scope of a safety engineer is the development and maintenance of the integrated management system. Safety engineering professionals must have a thorough understanding of legislation, standards and systems. They need to have a fundamental knowledge of safety , contract law , tort , environmental law , policy , health , construction , computer science , engineering , labour hire , plant hire , communication and psychology . Professional safety studies include construction and engineering , architectural design of systems , fire protection , ergonomics , system and process safety , system safety , safety and health program management, accident investigation and analysis, product safety , construction safety , education and training methods, measurement of safety performance , human behavior , environmental safety and health , and safety, health and environmental laws , regulations and standards. Many safety engineers have backgrounds or advanced study in other disciplines, such as occupational health and safety, construction management and civil engineering, engineering, system engineering / industrial engineering , requirements engineering , reliability engineering , maintenance , human factors , operations, education, physical and social sciences and other fields. This extends their expertise beyond the basics of health and safety.
They must be personally pleasant, intelligent, and ruthless with themselves and their organisation. In particular, they have to be able to "sell" the failures that they discover to inspectors/ auditors, as well as the attendant expense and time needed to correct them. Often facts can be uncomfortable for the business.
Safety engineers have to be ruthless about getting facts right from others, this includes from their fellow managers and engineers. It is common for a safety engineer to consider registers, plant and equipment, training and competency problems in the same day. Often the facts can be very uncomfortable.
Safety engineers work in a team that includes other engineering disciplines, project management, estimators, environmentalist, asset owners, regulators, doctors, auditors and lawyers.
Safety works well in a true risk matrix system, in which safety is a managed by the ISO3100 risk management system and integrated into the safety, quality and environment management systems. However, hierarchy of controls may be more suitable for smaller groups of less than 5 workers as it’s easier to digest. | https://en.wikipedia.org/wiki/Safety_engineer |
Safety in numbers is the hypothesis that, by being part of a large physical group or mass, an individual is less likely to be the victim of a mishap, accident , attack, or other bad event. Some related theories also argue (and can show statistically) [ citation needed ] that mass behaviour (by becoming more predictable and "known" to other people) can reduce accident risks, such as in traffic safety – in this case, the safety effect creates an actual reduction of danger, rather than just a redistribution over a larger group.
The mathematical biologist W.D. Hamilton proposed his selfish herd theory in 1971 to explain why animals seek central positions in a group. Each individual can reduce its own domain of danger by situating itself with neighbours all around, so it moves towards the centre of the group. [ 1 ] The effect was tested in brown fur seal predation by great white sharks . Using decoy seals, the distance between decoys was varied to produce different domains of danger. As predicted, the seals with a greater domain of danger had an increased risk of shark attack. [ 2 ] Antipredator adaptations include behaviour such as the flocking of birds, herding of sheep [ 3 ] and schooling of fish. [ 4 ] Similarly, Adelie penguins wait to jump into the water until a large enough group has assembled, reducing each individual's risk of seal predation. [ 5 ] This behavior is also seen in masting and predator satiation where the predators are overwhelmed with an abundance of prey during a period of time resulting in more of the prey surviving.
In 1949 R. J. Smeed reported that per capita road fatality rates tended to be lower in countries with higher rates of motor vehicle ownership. [ 6 ] This observation led to Smeed's Law .
In 2003 Peter L. Jacobsen [ 7 ] compared rates of walking and cycling, in a range of countries, with rates of collisions between motorists and cyclists or walkers. He found an inverse relationship that was hypothesised to be explained by a concept described as 'behavioural adaptation', whereby drivers who are exposed to greater numbers of cyclists on the road begin to drive more safely around them. Though an attractive concept for cycling advocates, it has not been empirically validated. Other combined modelling [ 8 ] [ 9 ] and empirical evidence suggests that while changes in driver behaviour might still be one way that collision risk per cyclist declines with greater numbers, [ 10 ] the effect can be easily produced through simple spatial processes (traffic design) akin to the biological herding processes described above. [ 11 ]
Without considering hypotheses 1 or 3, [ clarification needed ] Jacobsen concluded that "A motorist is less likely to collide with a person walking and bicycling if more people walk or bicycle." He described this theory as "safety in numbers." [ 7 ]
Safety in numbers is also used to describe the evidence that the number of pedestrians or cyclists correlates inversely with the risk of a motorist colliding with a pedestrian or cyclist . This non-linear relationship was first shown at intersections. [ 12 ] [ 13 ] It has been confirmed by ecologic data from cities in California and Denmark, and European countries, and time-series data for the United Kingdom and the Netherlands. [ 7 ] The number of pedestrians or bicyclists injured increases at a slower rate than would be expected based on their numbers. That is, more people walk or cycle where the risk to the individual pedestrian or bicyclist is lower. [ 14 ] [ 15 ] A 2002 study into whether pedestrian risk decreased with pedestrian flow, using 1983-86 data from signalized intersections in a town in Canada, found that in some circumstances pedestrian flow increased where the risk per pedestrian decreased. [ 16 ]
After cycling was promoted in Finland, there was a 75% drop in cyclists deaths and the number of trips increased by 72%. [ 17 ]
In England, between 2000 and 2008, serious bicycle injuries declined by 12%. Over the same period, the number of bicycle trips made in London doubled. [ 18 ] [ 19 ] [ 20 ] Motor vehicle traffic decreased by 16%, bicycle use increased by 28% and cyclist injuries had decreased by 20% in the first year of operation of the London Congestion Charge . [ 21 ] In January 2008, the number of cyclists in London being treated in hospitals for serious injuries had increased by 100% in six years. Over the same time, they report, the number of cyclists had increased by 84%. [ 22 ] In York, comparing the periods 1991-93 and 1996–98, the number of bicyclists killed and seriously injured fell by 59%. The share of trips made by bicycle rose from 15% to 18%. [ 23 ]
In Germany, between 1975 and 2001, the total number of bicycle trips made in Berlin almost quadrupled. Between 1990 and 2007, the share of trips made by bicycle increased from 5% to 10%. Between 1992 and 2006, the number of serious bicycle injuries declined by 38%. [ 24 ] [ 25 ] In Germany as a whole, between 1975 and 1998, cyclist fatalities fell by 66% and the percent of trips made by bicycle rose from 8% to 12%. [ 26 ]
In America, during the period 1999-2007, the absolute number of cyclists killed or seriously injured decreased by 29% and the amount of cycling in New York city increased by 98%. [ 27 ] [ 28 ] [ 29 ] In Portland, Oregon, between 1990 and 2000, the percentage of workers who commuted to work by bicycle rose from 1.1% to 1.8%. By 2008, the proportion has risen to 6.0%; while the number of workers increased by only 36% between 1990 and 2008, the number of workers commuting by bicycle increased 608%. Between 1992 and 2008, the number of bicyclists crossing four bridges into downtown was measured to have increased 369% between 1992 and 2008. During that same period, the number of reported crashes increased by only 14%. [ 30 ] [ 31 ] [ 32 ]
In Copenhagen, Denmark, between 1995 and 2006, the number of cyclists killed or seriously injured fell by 60%. During the same period, cycling increased by 44% and the percent of people cycling to work increased from 31% to 36%. [ 33 ]
In the Netherlands, between 1980 and 2005, and cyclist fatalities decreased by 58% and cycling increased by 45%. [ 34 ]
During 7 years of the 1980s, admissions to hospital of cyclists declined by 5% and cycling in Western Australia increased by 82%. [ 35 ] | https://en.wikipedia.org/wiki/Safety_in_numbers |
In functional safety a safety instrumented system ( SIS ) is an engineered set of hardware and software controls which provides a protection layer that shuts down a chemical, nuclear, electrical, or mechanical system, or part of it, if a hazardous condition is detected. [ 1 ]
An SIS performs a safety instrumented function (SIF) . The SIS is credited with a certain measure of reliability depending on its safety integrity level (SIL) . The required SIL is determined from a quantitative process hazard analysis (PHA), such as a Layers of Protection Analysis (LOPA). The SIL requirements are verified during the design, construction, installation, and operation of the SIS. The required functionality may be verified by design reviews, factory acceptance testing, site acceptance testing, and regular functional testing. The PHA is in turn based on a hazard identification exercise. In the process industries (oil and gas production, refineries , chemical plants , etc.), this exercise is usually a hazard and operability study (HAZOP). The HAZOP usually identifies not only the process hazards of a plant (such as release of hazardous materials due to the process operating outside the safe limits of the plant) but also the SIFs protecting the plant from such excursions. [ 1 ] [ 2 ]
An SIS is intended to perform specific control functions to prevent unsafe process operations when unacceptable or dangerous conditions occur. Because of its criticality, safety instrumented systems must be independent from all other control systems that control the same equipment, in order to ensure SIS functionality is not compromised. An SIS is composed of the same types of control elements (including sensors , logic solvers , actuators and other control equipment) as a Basic Process Control System (BPCS). However, all of the control elements in an SIS are dedicated solely to the proper functioning of the SIS.
The essential characteristic of an SIS is that it must include instruments, which detect that process variables (flow, temperature, pressure etc. in the case of a processing facility) are exceeding preset limits ( sensors ), a logic solver which processes this information and makes appropriate decisions based on the nature of the signal(s), and final elements which receive the output of the logic solver and take necessary action on the process to achieve a safe state. All these components must function properly for the SIS to perform its SIF. The logic solver may use electrical, electronic or programmable electronic equipment, such as relays , trip amplifiers , or programmable logic controllers . Support systems, such as power, instrument air, and communications, are generally required for SIS operation. The support systems should be designed to provide the required integrity and reliability . One example of SIS is a temperature sensor that provides a signal to a controller, which compares the sensed process temperature to the desired temperature setpoint and sends a signal to an emergency on-off valve actuator which stops the flow of heating fluid to the process if the process temperature is exceeded by an unsafe margin.
SIFs are implemented as part of an overall risk reduction strategy which is intended to minimize the likelihood of a previously identified accident that could range from minor equipment damage up to the uncontrolled catastrophic release of energy or materials.
The safe state must be achieved in a sufficiently short amount of time (known as process safety time ) to prevent the accident. [ 1 ] [ 2 ]
International standard IEC 61511 was published in 2003 to provide guidance to end-users on the application of Safety Instrumented Systems in the process industries . This standard is based on IEC 61508 , a generic standard for functional safety including aspects on design, construction, and operation of electrical/electronic/programmable electronic systems. Other industry sectors may also have standards that are based on IEC 61508, such as IEC 62061 (machinery systems), IEC 62425 (for railway signalling systems), IEC 61513 (for nuclear systems), and ISO 26262 (for road vehicles).
Other terms often used in conjunction with and/or to describe safety instrumented systems include: | https://en.wikipedia.org/wiki/Safety_instrumented_system |
A safety lamp is any of several types of lamp that provides illumination in places such as coal mines where the air may carry coal dust or a build-up of flammable gases, which may explode if ignited, possibly by an electric spark. Until the development of effective electric lamps in the early 1900s, miners used flame lamps to provide illumination. Open flame lamps could ignite flammable gases which collected in mines, causing explosions; safety lamps were developed to enclose the flame to prevent it from igniting the explosive gases. Flame safety lamps have been replaced for lighting in mining with sealed explosion-proof electric lights, but continue to be used to detect gases.
Miners have traditionally referred to the various gases encountered during mining as damps , from the Middle Low German word dampf (meaning " vapour "). [ 1 ] Damps are variable mixtures and are historic terms.
Before the invention of safety lamps, miners used candles with open flames. This gave rise to frequent explosions . For example, at one colliery (Killingworth) in the north east of England, 10 miners were killed in 1806 and 12 in 1809. In 1812, 90 men and boys were suffocated or burnt to death in the Felling Pit near Gateshead and 22 in the following year. [ 2 ]
Wood 1853 describes the testing of a mine for firedamp. A candle is prepared by being trimmed and excess fat removed. It is held at arm's length at floor level in one hand, the other hand shielding out all except the tip of the flame. As the candle is raised the tip is observed and if unchanged the atmosphere is safe. If however the tip turns bluish-gray increasing in height to a thin extended point becoming a deeper blue, then firedamp is present. [ 3 ] Upon detecting firedamp the candle is lowered and arrangements made for the ventilating of the area or the deliberate firing of the firedamp after the end of a shift. [ 4 ] To fire the gas, a man edged forward with a lit candle on the end of a stick. He kept his head down to allow the explosion to pass over him, but as soon as the explosion had occurred stood as upright as possible to avoid the afterdamp. Officially known as a fireman, he was also referred to as a penitent or monk from the hooded garb he wore as protection. The protective clothing was made of well-dampened wool or leather. This was a job with risk of injury, or to life. [ 4 ]
When they came into regular use, barometers were used to tell if atmospheric pressure was low, which could lead to more firedamp seeping out of the coal seams into the mine galleries. This continued to be essential information even after the introduction of safety lamps; at Trimdon Grange there was an accident involving pressure.
The lack of good lighting was a major cause of the eye affliction nystagmus . Miners working in thin seams or when undercutting the coal had to lie on their side in cramped conditions. The pick was swung horizontally to a point beyond the top of their head. In order to see where they were aiming (and accurate blows were needed), the eyes needed to be straining in what would normally be the upwards and slightly to one side direction. [ 5 ] This straining led first to temporary nystagmus and then to a permanent disability. Mild nystagmus would self-correct if a miner ceased to perform this work, but if left untreated would force a man to give up mining. [ 6 ] The lower levels of light emitted by safety lamps caused an increase in the incidence of nystagmus. [ 7 ]
In Europe and Britain dried fish skins which emitted a faint bioluminescence (often called phosphorescence) were used. [ 4 ] [ 8 ] [ 9 ]
Flint and steel mills introduced by Carlisle Spedding (1696–1755) before 1733 [ 10 ] had been tried with limited success. [ 11 ] An example of a Spedding steel mill may be seen in the museum at Whitehaven where Spedding was manager of the collieries of Sir James Lowther, 4th Baronet . [ 12 ] A steel disk was rotated at high speed by a crank mechanism. Pressing a flint against the disk produced a shower of sparks and dim illumination. [ 12 ] These mills were troublesome to use and were often worked by a boy, whose only task was to provide light for a group of miners. It was assumed that the sparks had insufficient energy to ignite firedamp until a series of explosions at Wallsend colliery in 1784; a further explosion in June 1785, which the operator of the mill survived, showed that ignition was possible. [ 13 ]
The first safety lamp made by William Reid Clanny used a pair of bellows to pump air through water to a candle burning in a metal case with a glass window. Exhaust gases passed out through water. The lamp was intrinsically safe provided it was kept upright, but gave out only a weak light. It was heavy and ungainly and required a man to pump it continuously. It was not a practical success, and Clanny subsequently changed the basis of operation of later lamps in the light of the Davy and Stephenson lamps. [ 11 ]
Safety lamps have to address the following issues:
Fire requires three elements to burn: fuel, oxidant and heat; the triangle of fire . Remove one element of this triangle and the burning will stop. A safety lamp has to ensure that the triangle of fire is maintained inside the lamp, but cannot pass to the outside.
Since any breathable atmosphere contains oxygen, and a safety lamp's raison d'être is to operate in an atmosphere also containing fuel (firedamp or coal dust), the element which must be blocked is heat. The key to manufacturing a successful safety lamp is to control the transfer of heat while still allowing air (the necessary oxidant) to enter and leave the lamp.
There are three main paths by which heat must be prevented from leaving the lamp:
In the Geordie lamp , the inlet and exhausts are kept separate. Restrictions in the inlet ensure that only just enough air for combustion passes through the lamp. A tall chimney contains the spent gases above the flame. If the percentage of firedamp starts to rise, less oxygen is available in the air and combustion is diminished or extinguished. Early Geordie lamps had a simple pierced copper cap over the chimney to further restrict the flow and to ensure that the vital spent gas did not escape too quickly. Later designs used metal mesh or gauze for the same purpose, and also as a barrier in itself. The inlet is through a number of fine tubes (early) or through a gallery (later). In the case of the gallery system air passes through a number of small holes into the gallery and through wire gauze to the lamp. The tubes both restrict the flow and ensure that any back flow is cooled. The flame front travels more slowly in narrow tubes (a key Stephenson observation) and allows the tubes to effectively stop such a flow.
In the Davy system, a metal gauze surrounds the flame and extends for a distance above forming a cage; flames do not pass through a fine enough mesh. All except the very earliest Davy lamps have a double layer at the top of the cage. Rising hot gases are cooled by the gauze, the metal conducting the heat away and being itself cooled by the incoming air. There is no restriction on the air entering the lamp; if firedamp is present it will get through the mesh and burn within the lamp itself, but without igniting gas outside. As the lamp burns brighter in dangerous atmospheres it acts as a warning to miners of rising firedamp levels. The Clanny configuration uses a short glass section around the flame with a gauze cylinder above it. Air is drawn in and descends just inside the glass, passing up through the flame in the centre of the lamp.
The outer casings of lamps are made of materials such as brass or tinned steel, which do not make a spark if they strike rock. [ 14 ]
Within months of Clanny's demonstration of his first lamp, two improved designs had been announced: one by George Stephenson , which later became the Geordie lamp , and the Davy lamp , invented by Sir Humphry Davy . Subsequently, Clanny incorporated aspects of both lamps and produced the ancestor of all modern oil safety lamps.
George Stephenson came from a mining family and by 1804 had secured the post of brakesman at Killingworth colliery. He was present at both the 1806 and 1809 explosions in the pit. By 1810, he was engineman and responsible for machinery both above and below ground. [ 15 ] The pit was a gassy pit and Stephenson took the lead in work to extinguish a fire in 1814. For some years prior to 1815 he had been experimenting on the blowers or fissures from which gas erupted. He reasoned that a lamp in a chimney could create a sufficient updraft that firedamp would not penetrate down the chimney. Further observations of the speed of flame fronts in fissures and passageways led him to design a lamp with fine tubes admitting the air.
Sir Humphry Davy was asked to consider the problems of a safety lamp following the Felling explosion. Previous experimenters had used coal gas (chiefly carbon monoxide) incorrectly, believing it to be the same as firedamp. Davy, however, performed his experiments with samples of firedamp collected from pits. As an experimental chemist, he was familiar with the inability of flames to pass through mesh; his experiments enabled him to determine the correct size and fineness for a miner's lamp.
Davy was awarded the Rumford Medal and £1,000 by the Royal Society in 1816 and a £2,000 prize by the country's colliery owners, [ 16 ] who also awarded 100 guineas (£105) to Stephenson. The Newcastle committee also awarded Stephenson a £1,000 prize collected by subscription. [ 17 ] Clanny was awarded a medal by the Royal Society of Arts in 1816. [ 11 ]
Both the Davy and Stephenson lamps were fragile. The gauze in the Davy lamp rusted in the damp air of a coal pit and became unsafe, while the glass in the Stephenson lamp was easily broken, and allowed the flame to ignite firedamp in the mine; later Stephenson designs also incorporated a gauze screen as a protection against glass breakage. [ 18 ] Developments, including the Gray, Mueseler and Marsaut lamps, tried to overcome these problems by using multiple gauze cylinders, but glass remained a problem until toughened glass became available. [ 19 ]
Improper use of safety lamps defeated the purpose of the safety lamp and caused risk. When the flame went out in a lamp there was a temptation for the collier to open and relight it. Some opened the lamps to light tobacco pipes underground. [ 20 ] Both of these practices were strictly forbidden. The miner was expected to return to the shaft, a round trip of up to a few miles, to relight an extinguished lamp. For men on piece work paid for what they produced, a relighting could cost them perhaps 10% of their day's pay, encouraging them to take the risk. Miners would also damage the mesh to make the lamp brighter. [ 21 ] To prevent dangerous relighting (or opening the lamp to light a pipe), from the mid-century onwards, and particularly after the 1872 act, lamps had to have a lock mechanism which prevented the miner opening the lamp. Two schemes existed: either a special tool was required which was kept at the pit head, or else opening the lamp extinguished the flame. The latter mechanism can be seen in the Mueseler, Landau, and Yates lamps below. Such a lamp was known as a protector lamp, a term picked up and used as a company name. [ 22 ] Only on the return to the bank could the lamp man open the lamp for refilling and service. Various different locking mechanisms were developed; miners tended to be ingenious in finding ways of circumventing them. A number of additional lit lamps were supposed to accompany each gang of men, but restricting the number was an obvious economy for the pit owners.
The light given out by these lamps was poor (particularly Davy's, obscured by the gauze); early lamps gave less light than candles. [ 23 ] This was not resolved until the introduction of electric lighting around 1900, and the introduction of battery-powered helmet lamps in 1930. The poor light provided yet another reason for miners to try to circumvent the locks.
The gauze in early lamps (the Davy, Geordie and Clanny) was exposed to air currents. It was quickly discovered that an air current could cause the flame, in effect, to pass through the gauze: the flame playing directly on the mesh heats it faster than the heat can be conducted away, increasing its temperature until sufficient to ignite the gas outside the lamp. [ 24 ]
The following data is compiled from Hunt 1879 , article: Safety lamps:
Following accidents such as Wallsend (1818), Trimdon Grange (1882) and the Bedford Colliery Disaster (1886), lamps had to be shielded against such currents. In the case of the Davy, a "Tin-can Davy" was developed which had a metal cylinder with perforations at the bottom and a glass window for the light from the gauze. Clanny derived lamps had a metal "bonnet" (typically of tinned iron) in the shape of a truncated cone covering the gauze above the glass cylinder. [ 25 ] The important point was that no direct current of air could impinge on the gauze itself. The shields had the disadvantage of not allowing the collier or the deputy to check that the gauze was in place and clean. Lamps were therefore made so that they could be inspected and then the bonnet placed on and locked.
Davy used a fine wire gauze with a mesh of 784 holes per square inch (28 mesh). The required fineness of the mesh was scrutinised by the Miners' Lamp Committee in 1924, 109 years after Davy's work, and a recommendation to use a coarser mesh of 400 holes/sq in (20 mesh) of 27 SWG wire was made. Lamps tested were as safe, and illumination increased, depending on lamp type, by between 16% and 32%. [ 26 ]
In the Davy lamp a standard oil lamp is surrounded by fine wire mesh or gauze, the top being closed by a double layer of gauze.
If firedamp is drawn into the flame it will burn more brightly and if the proportions are correct may even detonate. The flame on reaching the gauze fails to pass through and so the mine atmosphere is not ignited. However, if the flame is allowed to play on the gauze for a significant period, then it will heat up, sometimes as far as red heat. At this point it is effective, but in a dangerous state. Any further increase in temperature to white heat will ignite the external atmosphere. A sudden draught will case a localised hot spot and the flame will pass through. At a draught of between 4 and 6 feet per second the lamp becomes unsafe. [ 46 ] At Wallsend in 1818 lamps were burning red hot (indicating significant firedamp). A boy (Thomas Elliott) was employed to carry hot lamps to the fresh air and bring cool lamps back. For some reason he stumbled; the gauze was damaged and the damaged lamp triggered the explosion. [ 40 ] At Trimdon Grange (1882) a roof fall caused a sudden blast of air and the flame passed through the gauze with fatal results (69 killed). [ 45 ]
Poor copies and ill-advised "improvements" were known, but changing dimensions either reduced the illumination or the safety. [ 46 ] The poor light compared to either the Geordie or Clanny eventually led to the Davy being regarded as "not a lamp but a scientific instrument for detecting the presence of firedamp". [ 11 ] Some pits continued to use candles for illumination, relying on the Davy to warn men when to extinguish them.
In the earlier Geordie lamps an oil lamp is surrounded by glass. The top of the glass has a perforated copper cap with a metal gauze screen above that. The glass is surrounded by a perforated metal tube to protect it. Air ingress was via a series of tubes at the base.
Later versions used a metal gauze, instead of the perforated metal tube, to surround and protect the glass. Air intake was via an annular chamber around the base of the lamp (instead of previous tubes) into which air entered through small ( 1 ⁄ 20 ") holes then passed through gauze into the lamp. If the glass surrounding the lamp was broken, the Geordie became a Davy.
A strong enough current of air could travel through the tubes (later holes and gallery) and enlarge the flame, eventually leading to it becoming red-hot. [ 47 ] The lamp becomes unsafe in a current of from 8 to 12 feet per second, about twice that of the Davy. [ 47 ]
A development of the Geordie lamp was the Purdy. A galley with wire gauze provided the inlet, above the glass was a chimney with perforated copper cap and gauze outer. A brass tube protected the upper works, shielded them and kept them locked in position. A sprung pin locked the whole together. [ 48 ] The pin could only be released by applying a vacuum to a captive hollow screw; not something that a nicotine starved miner could do at the coal face [ citation needed ] .
Clanny abandoned his pumps and candles and developed a safety lamp which combined features of both the Davy and Geordie. The oil lamp was surrounded by a glass chimney with no ventilation from below. Above the chimney is a wire gauze cylinder with a double top. Air enters from the side and spent gases exit from the top. In the presence of firedamp the flame intensifies. The flame must be kept fairly high in normal use, a small flame permits the enclosed space to fill with firedamp/air mixture and the subsequent detonation may pass through the gauze. [ 49 ] A larger flame will keep the upper part full of burnt gas. The Clanny gives more light than the Davy and can be carried more easily in a draught. Lupton notes however it is superior in no other respect , particularly as a test instrument. [ 49 ]
The glass on a Clanny was secured by a large diameter brass ring which could be hard to tighten securely. If a splinter occurred at the end of a crack, or indeed any other unevenness, then the seal might be compromised. Such an incident occurred at Nicholson Pit in 1856 on a lamp being used by an overman to test for firedamp. The mines inspector recommended that only Stephenson lamps were used for illumination and Davys for testing. In particular "overmen ... whose lamps are mostly used to detect the presence gas [ sic ], should avoid such [Clanny] lamps". [ 18 ]
The lamp is a modified Clanny designed by the Belgian Mathieu-Louis Mueseler. The flame is surrounded by a glass tube surmounted by a wire gauze-capped cylinder. Air enters from the side above the glass and flows down to the flame before rising to exit at the top of the lamp. So far this is just a Clanny, but there is an internal chimney separating the rising combustion products from the incoming air. The chimney is supported by a gauze shelf through which incoming air must pass, forming a second barrier to back-propagating flames. [ 50 ] Some Mueseler lamps were fitted with a mechanism which locked the base of the lamp. Turning down the wick eventually released the base, but by then the flame was extinguished and therefore safe. [ 51 ]
The lamp was patented in 1840, and in 1864 the Belgian government made this type of lamp compulsory. [ 51 ]
In the presence of firedamp the explosive mixture is drawn through two gauzes (cylinder and shelf), burnt and then within the chimney are only burnt gases, not explosive mixture. Like a Clanny, and the Davy before it, it acts as an indicator of firedamp, burning more brightly in its presence. Later models had graduated shields by which the deputy could determine the concentration of firedamp from the heightening of the flame. Whilst the Clanny will continue to burn if laid on its side, potentially cracking the glass; the Mueseler will extinguish itself due to the stoppage of convection currents. The lamp is safe in currents up to 15 feet per second. [ 50 ]
The Marsaut lamp is a Clanny with multiple gauzes. Two or three gauzes are fitted inside each other, which improves the safety in a draught. Multiple gauzes, however, interfere with the air flow. The Marsaut was one of the first lamps to be fitted with a shield, in the illustration (right) the bonnet can be seen surrounding the gauzes. [ 52 ] A shielded Marsaut lamp can resist a current of 30 feet per second. [ 25 ]
The Bainbridge is a development of the Stephenson. A tapered glass cylinder surrounds the flame, and above that the body is a brass tube. The top of the tube is closed by a horizontal mesh attached to the body of the lamp by small bars to conduct heat away. Air enters through a series of small holes drilled in the lower brass ring supporting the glass. [ 24 ]
The lamp is in part a development of the Geordie. Air enters into a ring near the base which is protected by wire gauze or a perforated plate. The air passes down the side of the lamp passing through a series of gauze-covered holes, and enters the base through another yet another series of gauze-covered holes. Any attempt to unscrew the base causes the lever (shown at f in the illustration) to extinguish the flame. The gauze-covered holes and passageways restrict the flow to that required for combustion, so if any part of the oxygen is replaced by firedamp, then the flame is extinguished for want of oxidant. [ 24 ]
The upper portion of the lamp uses a chimney like in Mueseler and Morgan lamps. The rising gases pass up the chimney and through a gauze. At the top of the chimney a dished reflector diverts the gases out sideways through a number of holes in the chimney. The gases then start to rise up the intermediate chimney before exiting through another gauze. Gas finally passes down between the outermost chimney and the intermediate chimney, exiting a little above the glass. The outer chimney is therefore effectively a shield. [ 24 ]
The Yates lamp is a development of the Clanny. Air enters through the lower part of the gauze top and leaves through the upper part; there is no chimney. The lower glass part of the lamp has seen some development however. It is replaced by a silvered reflector having a strong lens or bull's-eye in it to allow the light out. The result was a claimed 20 fold improvement in lighting over the Davy. Yates claimed "the temptation to expose the flame to obtain more light is removed". [ 24 ]
The base also contained an interlocking mechanism to ensure that the wick was lowered and the lamp extinguished by any attempt to open it.
The lamp was "much more expensive than the forms of lamp now in general use, but Mr, Yates states that the saving of oil effected by its use will in one year pay the additional cost". [ 24 ]
The lamp devised and manufactured by Evan Thomas of Aberdare [ 53 ] is similar to a shielded Clanny, but there is a brass cylinder outside the gauze above the glass. It resists draughts well, but illumination is poor. [ 54 ]
The Morgan is a cross between the Mueseler and the Marsaut. It is a shielded lamp with a series of disks at the top to allow spent fumes out and a series of holes lower down the shield to allow air in. There is an inner and outer shield so that air cannot blow directly on the wire gauze but must first find its way through a slim chamber. There are multiple gauzes, like the Mersaut, and there is an internal chimney like the Mueseler. There is no "shelf" supporting the chimney, instead it hangs from an inverted gauze cone. [ 55 ]
The Morgan will resist air up to 53 feet per second and is "sufficiently safe for every practical purpose" . [ 55 ]
The Clifford also has a double shield, but with a plain flat top. The chimney is quite narrow with wire gauze covering the top. The bottom of the chimney has a glass bell covering the flame. The chimney is supported on a gauze shelf. Air enters through the lower part of the outer shield, through the passage and into the lamp through the inner shield. It is drawn down through the gauze, then passes the flame and ascends the chimney. At the top it leaves through gauze and the top of the double shield. The inner chimney is made of copper coated with a fusible metal: if the lamp gets too hot the metal melts and closes the air holes, extinguishing the lamp. [ 56 ]
The lamp has been tested and according to Lupton "successfully resisted every effort to explode it up to a velocity of more than 100 feet per second" . [ 56 ]
It was not until tungsten filaments replaced carbon that a portable electric light became a reality. [ citation needed ] An early pioneer was Joseph Swan who exhibited his first lamp in Newcastle upon Tyne in 1881 [ 44 ] and improved ones in subsequent years. The Royal Commission on Accidents in Mines set up in 1881 carried out extensive tests of all types of lamps and the final report in 1886 noted that there had been good progress made in producing electric lamps giving a light superior to that of oil lamps and expected economic and efficient lamps to become available soon. [ 57 ] This turned out not to be the case and progress was slow in attaining reliability and economy. The Sussmann lamp [ 58 ] was introduced into Britain in 1893 and following trials at Murton Colliery in Durham it became a widely used electric lamp with 3000 or so reported by the company in use in 1900 [ 59 ] However, by 1910 there were only 2055 electric lamps of all types in use – about 0.25% of all safety lamps. [ 60 ] In 1911, an anonymous colliery owner, through the British government, offered a prize of £1000 (equivalent to £129,000 in 2023 [ 37 ] ) for the best lamp to specified requirements. There were 195 entries. It was won by a German engineer with the CEAG lamp, [ 61 ] which was hand-held and delivered twice the illumination of oil lamps, with a battery life of 16 hours. [ 62 ] Awards were made to 8 other lamps that met the judges' criteria. [ 63 ] Clearly this stimulated development and over the next few years there was a marked increase in the use of electric lamps, especially the CEAG, Gray-Sussmann, and Oldham, so by 1922 there were 294,593 in use in Britain. [ 64 ]
In 1913, Thomas Edison won the Ratheman medal for inventing a lightweight storage battery that could be carried on the back, powering a parabolic reflector that could be mounted on the miner's helmet. [ 65 ] After extensive testing, 70,000 robust designs were in use in the US by 1916. [ 66 ]
Early electric lamps in Britain were hand-held as miners were used to this and helmet lamps became common much later than in countries like the US where helmet (cap) lamps had been the norm. [ 67 ]
Nowadays, safety lamps are mainly electric, and traditionally mounted on miners' helmets (such as the Wheat lamp or the Oldham headlamp [ 68 ] ), sealed to prevent gas penetrating the casing where it might be ignited by an electrical spark.
Although its use as a light source was superseded by electric lighting, the flame safety lamp has continued to be used in mines to detect methane and blackdamp , although many modern mines now use sophisticated electronic gas detectors for this purpose.
A newer light source, the light-emitting diode (LED), has advantages for safety lamps, mainly higher efficiency providing much longer illumination time from the same battery. Batteries too have improved and provide more energy per unit weight; LEDs in conjunction with batteries such as rechargeable lithium units provide much better performance in safety lamp applications. [ 69 ]
The Office of Mine Safety and Health (OMSHR), a part of the National Institute for Occupational Safety and Health (NIOSH) (itself part of Centers for Disease Control and Prevention) in the United States has been investigating the benefits of LED headlamps. A problem in mining is that the average age of miners is increasing (43.3 years in the US in 2013), and vision deteriorates with ages. [ 70 ] LED technology is physically robust compared to a filament light bulb, and has a longer life: 50,000 hours compared to 1,000 – 3,000. Extended life reduces light maintenance and failures; according to OMSHR an average of 28 accidents per year occur in US mines involving lighting. NIOSH has sponsored the development of cap lamp systems which they say improve the "ability of older subjects to detect moving hazards by 15% and trip hazards by 23.7%, and discomfort glare was reduced by 45%". [ 70 ] Conventional lights illuminate a narrow beam; NIOSH LED lamps are designed to produce a wider more diffuse beam which is claimed to improve the perception of objects by 79.5%. [ 70 ] | https://en.wikipedia.org/wiki/Safety_lamp |
The safety life cycle is the series of phases from initiation and specifications of safety requirements, covering design and development of safety features in a safety-critical system , and ending in decommissioning of that system. This article uses software as the context but the safety life cycle applies to other areas such as construction of buildings, for example. In software development, a process is used (software life cycle) and this process consists of a few phases, typically covering initiation, analysis, design, programming, testing and implementation. The focus is to build the software. Some software have safety concerns while others do not. For example, a Leave Application System does not have safety requirements. But we are concerned about safety if a software that is used to control the components in a plane fails. So for the latter, the question is how safety, being so important, should be managed within the software life cycle. [ 1 ]
The basic concept in building software safety, i.e. safety features in software, is that safety characteristics and behaviour of the software and system must be specified and designed into the system. [ 2 ]
The problem for any systems designer lies in reducing the risk to an acceptable level and of course, the risk tolerated will vary between applications. When a software application is to be used in a safety-related system, then this must be borne in mind at all stages in the software life cycle. The process of safety specification and assurance throughout the development and operational phases is sometimes called the ‘safety life cycle’.
The first stages of the life cycle involve assessing the potential system hazards and estimating the risk they pose. One such method is fault tree analysis .
This is followed by a safety requirements specification which is concerned with identifying safety-critical functions (functional requirements specification) and the safety integrity level for each of these functions. [ 3 ] The specification may either describe how the software should behave to minimize the risk or might require that the hazard should never arise.
A ‘normal’ process model is then followed with particular attention paid to the validation (inspection, testing etc.) of the system. Part of that validation should be an explicit safety validation activity.
Safety Life Cycle - Implementation Benefits and Impact on Field Devices (PDF) , ISA.org, archived from the original (PDF) on 31 March 2012 | https://en.wikipedia.org/wiki/Safety_life_cycle |
Safety pharmacology is a branch of pharmacology specialising in detecting and investigating potential undesirable pharmacodynamic effects of new chemical entities (NCEs) on physiological functions in relation to exposure in the therapeutic range and above. [ 1 ]
Primary organ systems (so-called core battery systems) are:
Secondary organ systems of interest are:
Safety pharmacology studies are required to be completed prior to human exposure (i.e., Phase I clinical trials), and regulatory guidance is provided in ICH S7A and other documents. [ 2 ] [ 3 ]
The aims of nonclinical safety pharmacology evaluations are three-fold:
The following key issues have to be considered within safety pharmacology: [ 4 ]
The first appearance of the term ‘safety pharmacology’ in the published literature dates back to 1980. [ 5 ] The term was certainly in common usage in the 1980s within the pharmaceutical industry to describe nonclinical pharmacological evaluation of unintended effects of candidate drugs for regulatory submissions. [ 6 ] Back then, it was part of a wider ‘general pharmacology’ assessment, which addressed actions of a drug candidate beyond the therapeutically intended effects. The only detailed guidelines indicating the requirements from drug regulatory authorities for general pharmacology studies were from the Ministry of Health, Labour, and Welfare . Nowadays, the term ‘general pharmacology’ is no longer used, and the ICH S7A guidelines [ 7 ] distinguish between primary pharmacodynamics (“studies on the mode of action and/or effects of a substance in relation to its desired therapeutic target”), secondary pharmacodynamics (“studies on the mode of action and/or effects of a substance not related to its desired therapeutic target”) and safety pharmacology (“studies that investigate the potential undesirable pharmacodynamic effects of a substance on physiological functions in relation to exposure in the therapeutic range and above.”).
A major stimulus to the discipline of safety pharmacology was the release in 1996 of a draft ‘Points to Consider’ document on QT prolongation by the European Medicines Agency's Committee for Proprietary Medicinal Products (CPMP), issued in final form the following year. [ 8 ] This initiative had been prompted by growing concern of sudden death caused by drug-induced torsade de pointes, a potentially lethal cardiac tachyarrhythmia. Later, in 2005, this concern was addressed by issue of the ICH S7B guidelines. [ 9 ]
Preclinical safety pharmacology integrates in silico , in vitro , and in vivo approaches. [ 10 ] In vitro safety pharmacology studies are focused on early hazard identification and subsequent compound profiling in order to guide preclinical in vivo safety and toxicity studies. Early compound profiling can flag for receptor-, enzyme-, transporter-, and ion channel-related liabilities of NCEs (e.g., inhibition of the human ether-a-go-go related gene protein ( hERG )). Classically, in vivo investigations comprise the use of young adult conscious animals.
Safety pharmacology studies have to be designed for defining the dose-response relationship of the adverse effect observed. Justification should be provided for the selection of the particular animal model or test system. The time course (e.g., onset and duration of response) of the adverse effect is investigated through selected time points for the measurements based on pharmacodynamic and pharmacokinetic considerations. Generally, the doses eliciting the adverse effect have to be compared to the doses eliciting the primary pharmacodynamic effect in the test species or the proposed therapeutic effect in humans.
The primary reference document for safety pharmacology is ICH S7A, followed by many key regulatory documents which either focus on or mention safety pharmacology: | https://en.wikipedia.org/wiki/Safety_pharmacology |
A safety sign is a sign designed to warn of hazards, indicate mandatory actions or required use of personal protective equipment , prohibit actions or objects, identify the location of firefighting or safety equipment , or marking of exit routes .
In addition to being encountered in industrial facilities; safety signs are also found in public places and communities, at electrical pylons and electrical substations , cliffs, beaches, bodies of water, on motorized equipment, such as lawn mowers, and areas closed for construction or demolition.
One of the earliest attempts to standardize safety signage in the United States was the
1914 Universal Safety Standards . [ 1 ] The signs were fairly simple in nature, consisting of an illuminated board with "DANGER" in white letters on a red field. [ 1 ] An arrow was added to draw attention to the danger if it was less obvious. Signs indicating exits, first aid kits consisted of a green board, with white letters. The goal with signs was to inform briefly. [ 1 ] The next major standards to follow were ASA [ a ] Z35.1 in 1941, revised in 1959, 1968, and 1972. [ 2 ] [ 3 ] [ 4 ] [ 5 ] The Occupational Safety and Health Administration devised their requirements from ASA Z35.1-1968 in the development of their rules, OSHA §1910.145 for the usage of safety signage in workplaces. [ 6 ]
In the 1980s, American National Standards Institute formed a committee to update the Z53 [ b ] and Z35 standards. In 1991, ANSI Z535 was introduced, which was intended to modernize signage through increased use of symbols, the introduction of a new header, 'Warning' and requiring that wording not just state the hazard, but also the possible harm the hazard could inflict and how to avoid the hazard. [ 7 ] Until 2013, OSHA regulations [ 8 ] technically required usage of signage prescribed in OSHA §1910.145, based on the standard ASA Z35.1-1968. Regulation changes and clarification of the law now allow usage of signs complying with either OSHA §1910.145 or ANSI Z535 designs. [ 9 ]
Prior to widespread globalization and adoption of standards from the ISO, most countries developed their own standards for safety signage. Text only signs were common prior to introduction of European Council Directive 77/576/EEC on 25 July 1977, which required member states to have policies in place to ensure that "safety signs at all places of work conform to the principles laid down in Annex I", which required color coding and symbols.
In 1992, the European Council Directive 92/58/EEC replaced EEC 77/576/EEC. The new directive included improved information on how to utilize safety signage effectively. Beyond safety signs, EEC Directive 92/58/EEC standardize markings for fire equipment, acoustic signals, verbal and hand signals for vehicle movements. [ 10 ] In 2013, the European Union adopted ISO 7010 to replace the symbols provided previously, adopting them as European Norm (EN) ISO 7010, standardizing symbols among the EU countries. Prior to this, while symbols were provided, symbols were permitted to vary in appearance "provided that they convey the same meaning and that no difference or adaptation obscures the meaning". [ 10 ]
Australian safety signage started in 1952 as CZ4-1952: Safety signs for the occupational environment . It was revised and redesignated as AS1319-1972 in 1972, with further revisions taking place in 1979, 1983 and 1994. [ 11 ] In August 2018, AS1319-1994 was reconfirmed as still being valid and not in need of major revisions. [ 11 ]
Japanese safety signage is notable for its clear visual differences from international norms, such as use of square 'no symbols', vertical formatting of sign text. Safety sign standards are regulated by Japanese Industrial Standards through standards JIS Z9101 (Workplace and public area safety signs) JIS Z 9103 (Safety sign colors) and JIS Z 9104 (Safety signs - General specifications). While design trends have been moving towards international norms of ISO standards, differences are still present such as the use of symbols unique to the JIS standards, using colors differently from ISO standards. [ d ] In addition to typical safety sign standards, Japan introduced JIS Z 9098 in 2016 specifically addressing emergency management needs: informing people of areas susceptible to natural disasters, evacuation routes and safe shelters from disasters. The standard's unique aspect is the usage of maps and diagrams to provide more detailed information about the area's hazards, shelters and evacuation routes. [ 12 ]
Chinese safety signage is regulated by Standardization Administration of China using GB standards 2893-2008 and 2894-2008, [ 13 ] [ 14 ] which all safety signs are legally required to comply with. [ 15 ] Designs are similar to ISO 3864 and uses older ISO 7010:2003 symbols, while adding several additional symbols covering a wider range of prohibitions and hazards. [ 14 ]
Modern signage design typically consists of a symbol, warning text, and in the United States, [ 6 ] [ 7 ] Canada, Australia [ 11 ] a header consisting of a signal word .
North American and some Australian safety signage utilize distinctive headers to draw attention to the risk of harm from a hazard. Headers have guidelines for usage, where conditions must be met to dictate which header must be used for a sign.
The 2007 revisions to ANSI Z353.4 allowed for the ' safety alert symbol ' found on 'Danger', Warning' and 'Caution' headers to be replaced with the ISO 7010 " W001 - General warning " symbol to enable compliance with ISO 3864-1 for signs used in international situations or equipment being exported abroad.
Additional headers designs exist, Z53.1-1968 prescribed a magenta and yellow 'Radiation' header for radiation hazards. Other headers have been created by sign manufacturers for various situations not covered by the Z53.1 standard, such as "Security Notice", "Biohazard", "Restricted Area".
As a means of overcoming language and literacy barriers, symbols depicting the hazards, required action or equipment, prohibited actions or items and safety equipment were introduced to safety signage during the 1990s. Globalization and increased international trade helped push this development, as a means of reducing costs associated with needing signage in multiple languages. [ 7 ] Increasingly, countries are adopting symbols used by ISO 7010 and UN Globally Harmonized System of Classification and Labelling of Chemicals , that harmonizes symbols internationally to reduce confusion, and bring themselves into compliance with international standards.
For temporary situations such as wet floors, portable signs are used. They are designed to be self supporting and relatively easy to move once the task is complete. The 1914 Universal Safety Standards [ 1 ] provided for a portable 'Danger' sign suitable for both hard floors and soft dirt. Portable signs can take a variety of forms, from a traffic cone with stick on letters, plastic a-frame signs, to safety signs mounted on poles with bases that enable movement. [ 16 ]
Wet floor signs are also intended to avoid legal liability from injury due to failing to warn of an unsafe condition. [ 17 ] They are usually yellow. [ 18 ] The warning is sometimes enhanced with new technology to provide audible warnings. [ 19 ] Robotic cleaning equipment can use wet floor signs with sonar gadgetry to know when its job is finished. [ 20 ]
Since the late 1980s, more emphasis has been put on testing signage for clarity and to eliminate possible misunderstandings. Researchers have examined the impacts of using different signal words, inclusion of borders and color contrast with text and symbols against sign backgrounds. [ 21 ] In 1999, a group of designers were tasked with creating standardized warning labels for personal watercraft . The group devised several versions of the same warning label using different symbols, wording and emphasis of key phrases through use of underlining, bold fonts and capitalizing. The label designs were reviewed by the United States Coast Guard , United States Power Squadron , industry representatives and subjected to ease of comprehension and readability tests. Results of these reviews and tests led to further revisions of words and redesigning of some symbols. [ 22 ] The resulting labels are still applied to personal watercraft nearly 20 years after their initial design. [ 23 ]
Placement of signs also affects the effectiveness of signs. A 1993 study tested compliance with a warning against loading the top drawer of a filing cabinet first. The warning was least effective when it was only placed on the shipping box, but most effective when placed as part of a removable cardboard sleeve that physically obstructed the top drawer, interfering with adding files to the drawer. [ 24 ]
Sign effectiveness can be reduced by a number of factors, including information overload , where the sheer amount of information is presented in a manner that a reader is unable to process adequately, such as being confronted by a sign consisting of dozens of words with no paragraph breaks, or excessive amounts of unnecessary information. [ e ] This can be prevented through simplifying warnings down to their key points, with supplementary manuals or training covering the more nuanced and minor information. Overwarning is a related problem, where warnings are overlooked by people due to the sheer number of warnings, such as placing many safety signs together, redundant or obvious warnings. [ 21 ] Effectiveness can be reduced through conditions such as poor maintenance, placing a sign too high or too low, or in a way that requires excessive effort to read. [ f ] [ 21 ] [ 10 ] | https://en.wikipedia.org/wiki/Safety_sign |
The safety testing of explosives involves the determination of various properties of the different energetic materials that are used in commercial, mining, and military applications. It is highly desirable to measure the conditions under which explosives can be set off for several reasons, including: safety in handling, safety in storage, and
safety in use.
It would be very difficult to provide an absolute scale for sensitivity with respect to the different properties of explosives . Therefore, it is generally required that one or more compounds be considered a standard for comparison to those compounds being tested. For example, PETN is considered to be a primary explosive by some individuals, and a secondary explosive by others. As a general rule, PETN is considered to be either a relatively insensitive primary explosive, or one of the most sensitive secondary explosives. PETN may be detonated by striking with a hammer on a hard steel surface (a very dangerous thing to do), and is generally considered the least sensitive explosive with which this may be done. For these facts and other reasons, PETN is considered one standard by which other explosives are gauged.
Another explosive that is used as a calibration standard is TNT , which was afforded the arbitrary Figure of Insensitivity of 100. Other explosives could then be compared against this standard.
Because there are different ways to set off explosives, there are several different components to the safety testing of explosives:
Used together, these numbers may be used to determine the potential threats afforded by energetic materials when employed in the field. It cannot be stressed enough that these figures are relative; when we determine that impact sensitivity of an explosive is lower for that of a tested explosive than PETN, for example, the number produced in the impact test is dimensionless, but it means that it is expected that it would take a greater impact to detonate it than PETN. Therefore, an experienced ordnance technician who works with raw PETN will know that the new explosive is not as sensitive with regards to impact. However, it could be more sensitive to friction, spark, or thermal issues. These conditions must be taken into account before any compound is to be stored, handled, or used in the field.
In the Netherlands , the Netherlands Organisation for Applied Scientific Research tests the safety of fireworks . [ 1 ] According to a 2017 report by the Dutch Safety Board , 25% of all fireworks tested failed to meet safety standards and were banned from sale. [ 2 ] Since 2010, safety testing of fireworks is required in the entire European Union , but companies are allowed to test their products in one member state before importing and selling them in another. [ 1 ] | https://en.wikipedia.org/wiki/Safety_testing_of_explosives |
A safety valve is a valve that acts as a fail-safe . An example of safety valve is a pressure relief valve (PRV), which automatically releases a substance from a boiler , pressure vessel , or other system , when the pressure or temperature exceeds preset limits. Pilot-operated relief valves are a specialized type of pressure safety valve. A leak tight, lower cost, single emergency use option would be a rupture disk .
Safety valves were first developed for use on steam boilers during the Industrial Revolution . Early boilers operating without them were prone to explosion unless carefully operated.
Vacuum safety valves (or combined pressure/vacuum safety valves) are used to prevent a tank from collapsing while it is being emptied, or when cold rinse water is used after hot CIP (clean-in-place) or SIP (sterilization-in-place) procedures. When sizing a vacuum safety valve, the calculation method is not defined in any norm, particularly in the hot CIP / cold water scenario, but some manufacturers [ 1 ] have developed sizing simulations.
The term safety valve is also used metaphorically .
The earliest and simplest safety valve was used on a 1679 steam digester and utilized a weight to retain the steam pressure (this design is still commonly used on pressure cookers ); however, these were easily tampered with or accidentally released. On the Stockton and Darlington Railway , the safety valve tended to go off when the engine hit a bump in the track. A valve less sensitive to sudden accelerations used a spring to contain the steam pressure, but these (based on a Salter spring balance ) could still be screwed down to increase the pressure beyond design limits. This dangerous practice was sometimes used to marginally increase the performance of a steam engine.
In 1856, John Ramsbottom invented a tamper-proof spring safety valve that became universal on railways. The Ramsbottom valve consisted of two plug-type valves connected to each other by a spring-laden pivoting arm, with one valve element on either side of the pivot. Any adjustment made to one of valves in an attempt to increase its operating pressure would cause the other valve to be lifted off its seat, regardless of how the adjustment was attempted. The pivot point on the arm was not symmetrically located between the valves, so any tightening of the spring would cause one of the valves to lift.
Only by removing and disassembling the entire valve assembly could its operating pressure be adjusted, making impromptu "tying down" of the valve by locomotive crews in search of more power impossible. The pivoting arm was commonly extended into a handle shape and fed back into the locomotive cab, allowing crews to 'rock' both valves off their seats to confirm that they were set and operating correctly.
Safety valves also evolved to protect equipment such as pressure vessels (fired or not) and heat exchangers . The term safety valve should be limited to compressible fluid applications (gas, vapour, or steam).
The two general types of protection encountered in industry are thermal protection and flow protection .
For liquid-packed vessels, thermal relief valves are generally characterized by the relatively small size of the valve necessary to provide protection from excess pressure caused by thermal expansion. In this case a small valve is adequate because most liquids are nearly incompressible, and so a relatively small amount of fluid discharged through the relief valve will produce a substantial reduction in pressure.
Flow protection is characterized by safety valves that are considerably larger than those mounted for thermal protection. They are generally sized for use in situations where significant quantities of gas or high volumes of liquid must be quickly discharged in order to protect the integrity of the vessel or pipeline. This protection can alternatively be achieved by installing a high integrity pressure protection system (HIPPS).
In the petroleum refining , petrochemical , chemical manufacturing , natural gas processing , power generation , food, drinks, cosmetics and pharmaceuticals industries, the term safety valve is associated with the terms pressure relief valve (PRV), pressure safety valve (PSV) and relief valve .
The generic term is Pressure relief valve (PRV) or pressure safety valve (PSV). PRVs and PSVs are not the same thing, despite what many people think; the difference is that PSVs have a manual lever to open the valve in case of emergency.
RV, SV and SRV are spring-operated (even spring-loaded). LPSV and VPSV are spring-operated or weight-loaded.
In most countries, industries are legally required to protect pressure vessels and other equipment by using relief valves. Also, in most countries, equipment design codes such as those provided by the ASME , API and other organizations like ISO (ISO 4126) must be complied with. These codes include design standards for relief valves and schedules for periodic inspection and testing after valves have been removed by the company engineer. [ 3 ] [ 4 ]
Today, the food, drinks, cosmetics, pharmaceuticals and fine chemicals industries call for hygienic safety valves, fully drainable and Cleanable-In-Place. Most are made of stainless steel; the hygienic norms are mainly 3A in the US and EHEDG in Europe.
The first safety valve was invented by Denis Papin for his steam digester , an early pressure cooker rather than an engine. [ 5 ] A weight acting through a lever held down a circular plug valve in the steam vessel. By using a " steelyard " lever a smaller weight was required, also the pressure could easily be regulated by sliding the same weight back and forth along the lever arm. Papin retained the same design for his 1707 steam pump. [ 6 ] [ 7 ]
Early safety valves were regarded as one of the engineman's controls and required continuous attention, according to the load on the engine. In a famous early explosion at Greenwich in 1803, one of Trevithick 's high-pressure stationary engines exploded when the boy trained to operate the engine left it to catch eels in the river, without first releasing the safety valve from its working load. [ 8 ] By 1806, Trevithick was fitting pairs of safety valves, one external valve for the driver's adjustment and one sealed inside the boiler with a fixed weight. This was unadjustable and released at a higher pressure, intended as a guarantee of safety. [ 9 ]
When used on locomotives, these valves would rattle and leak, releasing near-continuous puffs of waste steam.
Although the lever safety valve was convenient, it was too sensitive to the motion of a steam locomotive. Early steam locomotives therefore used a simpler arrangement of weights stacked directly upon the valve. This required a smaller valve area, so as to keep the weight manageable, which sometimes proved inadequate to vent the pressure of an unattended boiler, leading to explosions . An even greater hazard was the ease with which such a valve could be tied down, so as to increase the pressure and thus power of the engine, at further risk of explosion. [ 10 ]
Although deadweight safety valves had a short lifetime on steam locomotives, they remained in use on stationary boilers for as long as steam power remained. [ 11 ]
Weighted valves were sensitive to bouncing from the rough riding of early locomotives. One solution was to use a lightweight spring rather than a weight. This was the invention of Timothy Hackworth on his Royal George of 1828. [ 12 ] Owing to the limited metallurgy of the period, Hackworth's first spring valves used an accordion-like stack of multiple leaf springs . [ 13 ]
These direct-acting spring valves could be adjusted by tightening the nuts retaining the spring. To avoid tampering, they were often shrouded in tall brass casings which also vented the steam away from the locomotive crew.
The Salter coil spring spring balance for weighing, was first made in Britain by around 1770. [ 14 ] This used the newly developed spring steels to make a powerful but compact spring in one piece. Once again by using the lever mechanism, such a spring balance could be applied to the considerable force of a boiler safety valve.
The spring balance valve also acted as a pressure gauge. This was useful as previous pressure gauges were unwieldy mercury manometers and the Bourdon gauge had yet to be invented. [ 15 ]
The risk of firemen tying down the safety valve remained. [ 16 ] [ 17 ] This was encouraged by them being fitted with easily adjustable wing nuts, the practice of adjusting the boiler's working pressure via the safety valve being an accepted behaviour well into the 1850s. [ 18 ] [ 19 ] It was later common with Salter valves for them to be fitted in pairs, one adjustable and often calibrated for use as a gauge, the other sealed inside a locked cover to prevent tampering.
Paired valves were often adjusted to slightly different pressures too, a small valve as a control measure and the lockable valve made larger and permanently set to a higher pressure, as a safeguard. [ 12 ] [ 20 ] Some designs, such as one by Sinclair for the Eastern Counties Railway in 1859, had the valve spring with pressure scale behind the dome, facing the cab, and the locked valve ahead of the dome, out of reach of interference. [ 21 ]
In 1855, John Ramsbottom , later locomotive superintendent of the LNWR , described a new form of safety valve intended to improve reliability and especially to be tamper-resistant. A pair of plug valves were used, held down by a common spring-loaded lever between them with a single central spring. This lever was characteristically extended rearwards, often reaching into the cab on early locomotives.
Rather than discouraging the use of the spring lever by the fireman, Ramsbottom's valve encouraged this. Rocking the lever freed up the valves alternately and checked that neither was sticking in its seat. [ 22 ] Even if the fireman held the lever down and increased the force on the rear valve, there was a corresponding reduction of force on the forward valve. [ 12 ] [ 23 ]
Various forms of Ramsbottom valve were produced. Some were separate fittings to the boiler, through separate penetrations. [ 23 ] Others were contained in a U-shaped housing fastened to a single opening in the boiler shell. As boiler diameter increased, some forms were even set inside the boiler shell, with the springs housed in a recess inside and only the valves and balance lever protruding outside. [ 23 ] These had obvious drawbacks for easy maintenance. [ 24 ]
A drawback to the Ramsbottom type was its complexity. Poor maintenance or mis-assembly of the linkage between the spring and the valves could lead to a valve that no longer opened correctly under pressure. The valves could be held against their seats and fail to open or, even worse, to allow the valve to open but insufficiently to vent steam at an adequate rate and so not being an obvious and noticeable fault. [ 25 ] Mis-assembly of just this nature led to a fatal boiler explosion in 1909 at Cardiff on the Rhymney Railway , even though the boiler was almost new, at only eight months old. [ 26 ]
Naylor valve s were introduced around 1866. A bellcrank arrangement reduced the strain (percentage extension) of the spring, thus maintaining a more constant force. [ note 1 ] They were used by the L&Y and NER . [ 27 ]
All of the preceding safety valve designs opened gradually and had a tendency to leak a "feather" of steam as they approached "blowing-off", even though this was below the pressure. When they opened they also did so partially at first and did not vent steam quickly until the boiler was well over pressure. [ 12 ]
The quick-opening "pop" valve was a solution to this. Their construction was simple: the existing circular plug valve was changed to an inverted "top hat" shape, with an enlarged upper diameter. They fitted into a stepped seat of two matching diameters. When closed, the steam pressure acted only on the crown of the top hat, and was balanced by the spring force. Once the valve opened a little, steam could pass the lower seat and began to act on the larger brim. This greater area overwhelmed the spring force and the valve flew completely open with a "pop". Escaping steam on this larger diameter also held the valve open until pressure had dropped below that at which it originally opened, providing hysteresis . [ 12 ]
These valves coincided with a change in firing behaviour. Instead of letting steam reach a feather at the valve, firemen (stokers) now tried to avoid noisy blowing off, especially at platforms or under the large roof of a major station. This was mostly at the behest of stationmasters, but also because firemen realised that any blowing off through a pop valve wasted boiler pressure. In one case, this was estimated at 20 psi (140 kPa) lost corresponding to the burning of 16 lb (7.3 kg) or more of shovelled coal. [ note 2 ] [ 12 ]
Pop valves derived from Adams's patent design of 1873, with an extended lip. R. L. Ross's valves were patented in 1902 and 1904. They were more popular in America at first, but widespread from the 1920s on. [ 28 ]
Although polished brass safety valve coverings had been an early feature of steam locomotives, the only railway to maintain this tradition after pop valves were introduced was the Great Western Railway , with their distinctive tapered brass safety valve bonnets and copper-capped chimneys.
Developments in high-pressure water-tube boilers for marine use placed more demands on safety valves. Valves of greater capacity were required, to vent safely the high steam-generating capacity of these large boilers. [ 29 ] As the force on their valves increased, the issue of the spring's increasing stiffness as its load increased (like the Naylor valve ) became more critical. [ 30 ] The need to reduced valve feathering became even more important with high-pressure boilers, as this represented both a loss of distilled feedwater and also a scouring of the valve seats, leading to wear. [ 29 ]
High-lift safety valves are direct-loaded spring types, although the spring does not bear directly on the valve, but on a guide-rod valve stem. The valve is beneath the base of the stem, the spring rests on a flange some height above this. The increased space between the valve itself and the spring seat allows the valve to lift higher, further clear of the seat. This gives a steam flow through the valve equivalent to a valve one and a half or twice as large (depending on detail design). [ 30 ]
The Cockburn Improved High Lift design has similar features to the Ross pop type. The exhaust steam is partially trapped on its way out and acts on the base of the spring seat, increasing the lift force on the valve and holding the valve further open. [ 30 ]
To optimise the flow through a given diameter of valve, the full-bore design is used. This has a servo action, where steam through a narrow control passage is allowed through if it passes a small control valve. This steam is then not exhausted, but is passed to a piston that is used to open the main valve. [ 29 ]
There are safety valves known as PSV's and can be connected to pressure gauges (usually with a 1/2" BSP fitting). These allow a resistance of pressure to be applied to limit the pressure forced on the gauge tube, resulting in prevention of over pressurisation. the matter that has been injected into the gauge, if over pressurised, will be diverted through a pipe in the safety valve, and shall be driven away from the gauge.
There is a wide range of safety valves having many different applications and performance criteria in different areas. In addition, national standards are set for many kinds of safety valves.
Safety valves are required on water heaters , where they prevent disaster in certain configurations in the event that a thermostat should fail. Such a valve is sometimes referred to as a "T&P valve" (Temperature and Pressure valve). There are still occasional, spectacular failures of older water heaters that lack this equipment. Houses can be leveled by the force of the blast. [ 33 ]
Pressure cookers are cooking pots with a pressure-proof lid. Cooking at pressure allows the temperature to rise above the normal boiling point of water (100 degrees Celsius at sea level ), which speeds up the cooking and makes it more thorough.
Pressure cookers usually have two safety valves to prevent explosions. On older designs, one is a nozzle upon which a weight sits. The other is a sealed rubber grommet which is ejected in a controlled explosion if the first valve gets blocked. On newer generation pressure cookers, if the steam vent gets blocked, a safety spring will eject excess
pressure and if that fails, the gasket will expand and release excess pressure downwards between the lid and the pan.
Newer generation pressure cookers have a safety interlock which locks the lid when internal pressure exceeds atmospheric pressure, to prevent accidents from a sudden release of very hot steam, food and liquid, which would happen if the lid were to be removed when the pan is still slightly pressurised inside (however, the lid will be very hard or impossible to open when the pot is still pressurised). | https://en.wikipedia.org/wiki/Safety_valve |
The Saffman–Delbrück model describes a lipid membrane as a thin layer of viscous fluid , surrounded by a less viscous bulk liquid. This picture was originally proposed to determine the diffusion coefficient of membrane proteins, but has also been used to describe the dynamics of fluid domains within lipid membranes. The Saffman–Delbrück formula is often applied to determine the size of an object embedded in a membrane from its observed diffusion coefficient , and is characterized by the weak logarithmic dependence of diffusion constant on object radius.
In a three-dimensional highly viscous liquid, a spherical object of radius a has diffusion coefficient
by the well-known Stokes–Einstein relation . By contrast, the diffusion coefficient of a circular object embedded in a two-dimensional fluid diverges; this is Stokes' paradox . In a real lipid membrane, the diffusion coefficient may be limited by:
Philip Saffman and Max Delbrück calculated the diffusion coefficient for these three cases, and showed that Case 3 was the relevant effect. [ 1 ]
The diffusion coefficient of a cylindrical inclusion of radius a {\displaystyle a} in a membrane with thickness h {\displaystyle h} and viscosity η m {\displaystyle \eta _{m}} , surrounded by bulk fluid with viscosity η f {\displaystyle \eta _{f}} is:
where the Saffman–Delbrück length L s d = h η m 2 η f {\displaystyle L_{sd}={\frac {h\eta _{m}}{2\eta _{f}}}} and γ ≈ 0.577 {\displaystyle \gamma \approx 0.577} is the Euler–Mascheroni constant . Typical values of L s d {\displaystyle L_{sd}} are 0.1 to 10 micrometres. [ 2 ] This result is an approximation applicable for radii a ≪ L s d {\displaystyle a\ll L_{sd}} , which is appropriate for proteins ( a ≈ {\displaystyle a\approx } nm), but not for micrometre-scale lipid domains.
The Saffman–Delbrück formula predicts that diffusion coefficients D s d {\displaystyle D_{sd}} will only depend weakly on the size of the embedded object; for example, if L s d = 1 μ m {\displaystyle L_{sd}=1\mu m} , changing a {\displaystyle a} from 1 nm to 10 nm only reduces the diffusion coefficient D s d {\displaystyle D_{sd}} by 30%.
Hughes, Pailthorpe, and White extended the theory of Saffman and Delbrück to inclusions with any radii a {\displaystyle a} ; [ 3 ] for a ≫ L s d {\displaystyle a\gg L_{sd}} ,
A useful formula that produces the correct diffusion coefficients between these two limits is [ 2 ]
where ϵ = a / L s d {\displaystyle \epsilon =a/L_{sd}} , b 1 = 2.74819 {\displaystyle b_{1}=2.74819} , b 2 = 0.51465 {\displaystyle b_{2}=0.51465} , c 1 = 0.73761 {\displaystyle c_{1}=0.73761} , and c 2 = 0.52119 {\displaystyle c_{2}=0.52119} . Please note that the original version of [ 2 ] has a typo in b 2 {\displaystyle b_{2}} ; the value in the correction [ 4 ] to that article should be used.
Though the Saffman–Delbruck formula is commonly used to infer the sizes of nanometer-scale objects, recent controversial [ 5 ] experiments on proteins have suggested that the diffusion coefficient's dependence on radius a {\displaystyle a} should be a − 1 {\displaystyle a^{-1}} instead of ln ( a ) {\displaystyle \ln(a)} . [ 6 ] However, for larger objects (such as micrometre-scale lipid domains ), the Saffman–Delbruck model (with the extensions above) is well-established [ 2 ] [ 7 ] [ 8 ]
The Saffman–Delbrück approach has also been extended in recent works for modeling hydrodynamic interactions between proteins embedded within curved lipid bilayer membranes, such as in vesicles and other structures. [ 9 ] [ 10 ] [ 11 ] [ 12 ] These works use related formulations to study the roles of the membrane hydrodynamic coupling and curvature in the collective drift-diffusion dynamics of proteins within bilayer membranes. Various models of the protein inclusions within curved membranes have been developed, including models based on series truncations, [ 9 ] immersed boundary methods , [ 11 ] and fluctuating hydrodynamics. [ 12 ] | https://en.wikipedia.org/wiki/Saffman–Delbrück_model |
The Saffman–Taylor instability , also known as viscous fingering , is the formation of patterns in a morphologically unstable interface between two fluids in a porous medium or in a Hele-Shaw cell , described mathematically by Philip Saffman and G. I. Taylor in a paper of 1958. [ 1 ] [ 2 ] This situation is most often encountered during drainage processes through media such as soils. [ 3 ] It occurs when a less viscous fluid is injected, displacing a more viscous fluid; in the inverse situation, with the more viscous displacing the other, the interface is stable and no instability is seen. Essentially the same effect occurs driven by gravity (without injection) if the interface is horizontal and separates two fluids of different densities, the heavier one being above the other: this is known as the Rayleigh–Taylor instability . In the rectangular configuration the system evolves until a single finger (the Saffman–Taylor finger) forms, whilst in the radial configuration the pattern grows forming fingers by successive tip-splitting. [ 4 ]
Most experimental research on viscous fingering has been performed on Hele-Shaw cells, which consist of two closely spaced, parallel sheets of glass containing a viscous fluid. The two most common set-ups are the channel configuration, in which the less viscous fluid is injected at one end of the channel, and the radial configuration, in which the less viscous fluid is injected at the centre of the cell. Instabilities analogous to viscous fingering can also be self-generated in biological systems. [ 5 ]
The simplest case of the instability arises at a planar interface within a porous medium or Hele-Shaw cell, and was treated by Saffman and Taylor [ 1 ] but also earlier by other authors. [ 6 ] A fluid of viscosity μ 1 {\displaystyle \mu _{1}} is driven in the x {\displaystyle x} -direction into another fluid of viscosity μ 2 {\displaystyle \mu _{2}} at some velocity V {\displaystyle V} . Denoting the permeability of the porous medium as a constant, isotropic, Π {\displaystyle \Pi } , Darcy's law gives the unperturbed pressure fields in the two fluids i = 1 , 2 {\displaystyle i=1,\,2} to be p i ( 0 ) = p int − V μ i Π x , {\displaystyle p_{i}^{(0)}=p_{\text{int}}-{\frac {V\mu _{i}}{\Pi }}x,} where p int {\displaystyle p_{\text{int}}} is the pressure at the planar interface, working in a frame where this interface is instantaneously given by x = 0 {\displaystyle x=0} . Perturbing this interface to x = η 0 exp ( i k y + σ t ) {\displaystyle x=\eta _{0}\exp {\left(\mathrm {i} ky+\sigma t\right)}} (decomposing into normal modes in the x − y {\displaystyle x-y} plane, and taking | η 0 | ≪ 1 {\displaystyle \left|\eta _{0}\right|\ll 1} ), the pressure fields become p i = p i ( 0 ) + p ~ i ( x ) exp ( i k y + σ t ) . {\displaystyle p_{i}=p_{i}^{(0)}+{\tilde {p}}_{i}\left(x\right)\exp {\left(\mathrm {i} ky+\sigma t\right)}.} As a consequence of the incompressibility of the flow and Darcy's law, the pressure fields must be harmonic , which, coupled with the requirement that the perturbation decay as x → ± ∞ {\displaystyle x\to \pm \infty } , fixes p ~ 1 = p ~ 1 e k x {\displaystyle {\tilde {p}}_{1}={\tilde {p}}_{1}e^{kx}} and p ~ 2 = p ~ 2 e − k x {\displaystyle {\tilde {p}}_{2}={\tilde {p}}_{2}e^{-kx}} , with the constants p ~ {\displaystyle {\tilde {p}}} to be determined by continuity of pressure. Upon linearization , the kinematic boundary condition at the interface (that fluid velocity in the x {\displaystyle x} direction must match the velocity of the fluid interface), coupled with Darcy's law, gives − Π μ i ∂ p ~ i ∂ x | x = 0 = σ η 0 , {\displaystyle -{\frac {\Pi }{\mu _{i}}}\left.{\frac {\partial {\tilde {p}}_{i}}{\partial x}}\right|_{x=0}=\sigma \eta _{0},} and thus that p ~ 1 = − σ η 0 μ 1 Π k {\displaystyle {\tilde {p}}_{1}=-{\frac {\sigma \eta _{0}\mu _{1}}{\Pi k}}} and p ~ 2 = σ η 0 μ 2 Π k {\displaystyle {\tilde {p}}_{2}={\frac {\sigma \eta _{0}\mu _{2}}{\Pi k}}} . Matching the pressure fields at the interface gives − V μ 1 − σ μ 1 k = − V μ 2 + σ μ 2 k , {\displaystyle -V\mu _{1}-{\frac {\sigma \mu _{1}}{k}}=-V\mu _{2}+{\frac {\sigma \mu _{2}}{k}},} and so σ = k V ( μ 2 − μ 1 ) / ( μ 1 + μ 2 ) {\displaystyle \sigma =kV\left(\mu _{2}-\mu _{1}\right)/\left(\mu _{1}+\mu _{2}\right)} , leading to growth of the perturbation when μ 2 > μ 1 {\displaystyle \mu _{2}>\mu _{1}} - i.e. when the injected fluid is less viscous than the ambient fluid. There are problems with this basic case: namely that the most unstable mode has infinite wavenumber k {\displaystyle k} and grows at an infinitely fast rate, which can be rectified by the introduction of surface tension [ 7 ] (which provides a jump condition in pressures across the fluid interface through the Young–Laplace equation ), which has the effect of modifying the growth rate to
σ = k V ( μ 2 − μ 1 ) − γ H f k 3 μ 1 + μ 2 , {\displaystyle \sigma ={\frac {kV\left(\mu _{2}-\mu _{1}\right)-\gamma H_{f}k^{3}}{\mu _{1}+\mu _{2}}},}
with surface tension γ {\displaystyle \gamma } and H f {\displaystyle H_{f}} the mean curvature . This suppresses small-wavelength (high-wavenumber) disturbances, and we would expect to see instabilities with wavenumber k {\displaystyle k} close to the value of k {\displaystyle k} which results in the maximal value of σ {\displaystyle \sigma } ; in this case with surface tension, there is a unique maximal value.
The Saffman–Taylor instability is usually seen in an axisymmetric context as opposed to the simple planar case derived above. [ 8 ] [ 9 ] The mechanisms for the instability remain the same in this case, and the selection of the most unstable wavenumber in this case corresponds to a given number of fingers (an integer). | https://en.wikipedia.org/wiki/Saffman–Taylor_instability |
Safranin ( Safranin O or basic red 2 ) is a biological stain used in histology and cytology . Safranin is used as a counterstain in some staining protocols, colouring cell nuclei red. This is the classic counterstain in both Gram stains and endospore staining . It can also be used for the detection of cartilage , [ 2 ] mucin and mast cell granules.
Safranin typically has the chemical structure shown at right (sometimes described as dimethyl safranin ). There is also trimethyl safranin , which has an added methyl group in the ortho- position (see Arene substitution pattern ) of the lower ring. Both compounds behave essentially identically in biological staining applications, and most manufacturers of safranin do not distinguish between the two. Commercial safranin preparations often contain a blend of both types.
Safranin is also used as redox indicator in analytical chemistry .
Safranines are the azonium compounds of symmetrical 2,8-dimethyl-3,7-diaminophenazine. They are obtained by the joint oxidation of one molecule of a para -diamine with two molecules of a primary amine ; by the condensation of para -aminoazo compounds with primary amines, and by the action of para -nitrosodialkylanilines with secondary bases such as diphenylmetaphenylenediamine. They are crystalline solids showing a characteristic green metallic lustre ; they are readily soluble in water and dye red or violet. They are strong bases and form stable monacid salts . Their alcoholic solution shows a yellow-red fluorescence . [ 3 ]
Phenosafranine is not very stable in the free state [ citation needed ] ; its chloride forms green plates [ clarification needed ] . It can be readily diazotized, and the diazonium salt when boiled with alcohol yields aposafranine or benzene induline, C 18 H 12 N 3 . Friedrich Kehrmann showed that aposafranine could be diazotized in the presence of cold concentrated sulfuric acid , and the diazonium salt on boiling with alcohol yielded phenylphenazonium salts. Aposafranone, C 18 H 12 N 2 O, is formed by heating aposafranine with concentrated hydrochloric acid . These three compounds are perhaps to be represented as ortho - or as para - quinones . The "safranine" of commerce is an ortho -tolusafranine. The first aniline dye-stuff to be prepared on a manufacturing scale was mauveine , which was obtained by Sir William Henry Perkin by heating crude aniline with potassium dichromate and sulfuric acid. [ 3 ]
Mauveine was converted to parasafranine (1,8-dimethylsafranine) by Perkin in 1878 by oxidative / reductive loss of the 7 N - para -tolyl group. [ 4 ] Another well known safranin is phenosafranine (C.I. 50200, 3,7-diamino-5-phenylphenazinium chloride) widely used as a histological dye, photosensitizer and redox probe. [ 5 ] | https://en.wikipedia.org/wiki/Safranin |
Paint and other coatings that are on slanted or vertical surfaces tend to sag when first applied. The thickness of the coating as well as the composition and viscosity will affect the overall sagging and conversely the sag resistance. In order to find the sag resistance of a coating a simple test is used. A metal applicator bar is used along with a Drawdown card .
The applicator is U-shaped and is manufactured with a set of 1/4 inch (6.4 mm) wide notches. The notches are spaced 1/16 inch (1.6 mm) apart. The applicator bar is 5 inches (127 mm) wide and
leaves 3 3/8 inches (86 mm) of applied coating behind after use. After the bar is drawn down the card with the coating, a series of parallel stripes with varying film thickness will be formed. The card is then placed on a vertical surface with the thickest of the stripes at the bottom. The coating will then sag downward and the clearance of the gap that produces the thickest film stripe, not sagging completely to the stripe below, is the anti-sag index of the coating. [ 1 ]
https://www.tqc.eu/en/product/filmapplicator-for-sag-and-levelling-en/ | https://en.wikipedia.org/wiki/Sag_resistance_test |
SageMath (previously Sage or SAGE , "System for Algebra and Geometry Experimentation" [ 3 ] ) is a computer algebra system (CAS) with features covering many aspects of mathematics , including algebra , combinatorics , graph theory , group theory , differentiable manifolds , numerical analysis , number theory , calculus and statistics .
The first version of SageMath was released on 24 February 2005 as free and open-source software under the terms of the GNU General Public License version 2, with the initial goals of creating an "open source alternative to Magma , Maple , Mathematica , and MATLAB ". [ 4 ] The originator and leader of the SageMath project, William Stein , was a mathematician at the University of Washington .
SageMath uses a syntax resembling Python 's, [ 5 ] supporting procedural , functional and object-oriented constructs.
Stein realized when designing Sage that there were many open-source mathematics software packages already written in different languages , namely C , C++ , Common Lisp , Fortran and Python .
Rather than reinventing the wheel , Sage (which is written mostly in Python and Cython ) integrates many specialized CAS software packages into a common interface, for which a user needs to know only Python. However, Sage contains hundreds of thousands of unique lines of code adding new functions and creating the interfaces among its components. [ 6 ]
SageMath uses both students and professionals for development. The development of SageMath is supported by both volunteer work and grants . [ 7 ] However, it was not until 2016 that the first full-time Sage developer was hired (funded by an EU grant). [ 8 ] The same year, Stein described his disappointment with a lack of academic funding and credentials for software development, citing it as the reason for his decision to leave his tenured academic position to work full-time on the project in a newly founded company, SageMath, Inc. [ 8 ]
Both binaries and source code are available for SageMath from the download page. If SageMath is built from source code, many of the included libraries such as OpenBLAS , FLINT , GAP (computer algebra system) , and NTL will be tuned and optimized for that computer, taking into account the number of processors , the size of their caches , whether there is hardware support for SSE instructions, etc.
Cython can increase the speed of SageMath programs, as the Python code is converted into C . [ 12 ]
SageMath is free software , distributed under the terms of the GNU General Public License version 3. [ 2 ]
SageMath 10.0 (May 2023) requires Windows Subsystem for Linux in version 2, [ 13 ] which in turn requires Windows to run as a Hyper-V client. SageMath 8.0 (July 2017), with development funded by the OpenDreamKit project, [ 8 ] successfully built on Cygwin , and a binary installer for 64-bit versions of Windows was available. [ 14 ] Although Microsoft was sponsoring a Windows version of SageMath, prior to 2016 users of Windows had to use virtualization technology such as VirtualBox to run SageMath. [ 15 ]
SageMath is available as a package in some Linux distributions , including Arch Linux , Debian , Ubuntu and NixOS . In Gentoo , it is available via layman in the "sage-on-gentoo" [ 16 ] overlay. The package used by NixOS is available for use on other distributions, due to the distribution-agnostic nature of its package manager, Nix .
Gentoo prefix also provides Sage on other operating systems.
The philosophy of SageMath is to use existing open-source libraries wherever they exist. Therefore, it uses many libraries from other projects. | https://en.wikipedia.org/wiki/SageMath |
SageManifolds (following the styling of SageMath) is an extension fully integrated into SageMath , to be used as a package for differential geometry and tensor calculus . The official page for the project is sagemanifolds.obspm.fr . It can be used on CoCalc .
SageManifolds deals with differentiable manifolds of arbitrary dimension. The basic objects are tensor fields and not tensor components in a given vector frame or coordinate chart. In other words, various charts and frames can be introduced on the manifold and a given tensor field can have representations in each of them.
An important class of treated manifolds is that of pseudo-Riemannian manifolds , among which Riemannian manifolds and Lorentzian manifolds , with applications to General Relativity . In particular, SageManifolds implements the computation of the Riemann curvature tensor and associated objects ( Ricci tensor , Weyl tensor ). SageManifolds can also deal with generic affine connections , not necessarily Levi-Civita ones.
This release propagates further code changes related to the integration of SageManifolds into SageMath (cf. the metaticket#18528); it also adds a few new functionalities.
New functionalities:
Syntactic changes:
More internal changes:
Syntactic changes:
Internal changes:
Other changes:
More documentation is on doc.sagemath.org/html/en/reference/manifolds/ .
As SageMath is, SageManifolds is a free and open source software based on the Python programming language. It is released under the GNU General Public License . To download and install SageManifolds, see here . It is more specifically GPL v2+ (meaning that a user may elect to use a licence higher than GPL version 2.)
Much of the source is on tickets at trac.sagemath.org .
There are GitHub repositories at github.com/sagemanifolds/SageManifolds .
Other links are provided at sagemanifolds.obspm.fr/contact.html . | https://en.wikipedia.org/wiki/Sage_Manifolds |
In geometry , the sagitta (sometimes abbreviated as sag [ 1 ] ) of a circular arc is the distance from the midpoint of the arc to the midpoint of its chord . [ 2 ] It is used extensively in architecture when calculating the arc necessary to span a certain height and distance and also in optics where it is used to find the depth of a spherical mirror or lens. The name comes directly from Latin sagitta , meaning an " arrow ".
In the following equations, s {\displaystyle s} denotes the sagitta (the depth or height of the arc), r {\displaystyle r} equals the radius of the circle , and l {\displaystyle l} the length of the chord spanning the base of the arc. As 1 2 l {\displaystyle {\tfrac {1}{2}}l} and r − s {\displaystyle r-s} are two sides of a right triangle with r {\displaystyle r} as the hypotenuse , the Pythagorean theorem gives us
This may be rearranged to give any of the other three:
The sagitta may also be calculated from the versine function, for an arc that spans an angle of Δ = 2 θ , and coincides with the versine for unit circles
When the sagitta is small in comparison to the radius, it may be approximated by the formula [ 2 ]
Alternatively, if the sagitta is small and the sagitta, radius, and chord length are known, they may be used to estimate the arc length by the formula
where a is the length of the arc ; this formula was known to the Chinese mathematician Shen Kuo , and a more accurate formula [ clarification needed ] also involving the sagitta was developed two centuries later by Guo Shoujing . [ 3 ]
Architects, engineers, and contractors use these equations to create "flattened" arcs that are used in curved walls, arched ceilings, bridges, and numerous other applications.
The sagitta also has uses in physics where it is used, along with chord length, to calculate the radius of curvature of an accelerated particle. This is used especially in bubble chamber experiments where it is used to determine the momenta of decay particles. Likewise historically the sagitta is also utilised as a parameter in the calculation of moving bodies in a centripetal system. This method is utilised in Newton's Principia . | https://en.wikipedia.org/wiki/Sagitta_(geometry) |
The Sagnac effect , also called Sagnac interference , named after French physicist Georges Sagnac , is a phenomenon encountered in interferometry that is elicited by rotation . The Sagnac effect manifests itself in a setup called a ring interferometer or Sagnac interferometer . A beam of light is split and the two beams are made to follow the same path but in opposite directions. On return to the point of entry the two light beams are allowed to exit the ring and undergo interference . The relative phases of the two exiting beams, and thus the position of the interference fringes, are shifted according to the angular velocity of the apparatus. In other words, when the interferometer is at rest with respect to a nonrotating frame , the light takes the same amount of time to traverse the ring in either direction. However, when the interferometer system is spun, one beam of light has a longer path to travel than the other in order to complete one circuit of the mechanical frame, and so takes longer, resulting in a phase difference between the two beams. Georges Sagnac set up this experiment in 1913 in an attempt to prove the existence of the aether that Einstein's theory of special relativity makes superfluous. [ 1 ] [ 2 ]
A gimbal mounted mechanical gyroscope remains pointing in the same direction after spinning up, and thus can be used as a rotational reference for an inertial navigation system . With the development of so-called laser gyroscopes and fiber optic gyroscopes based on the Sagnac effect, bulky mechanical gyroscopes can be replaced by those with no moving parts in many modern inertial navigation systems. A conventional gyroscope relies on the principle of conservation of angular momentum whereas the sensitivity of the ring interferometer to rotation arises from the invariance of the speed of light for all inertial frames of reference .
Typically three or more mirrors are used, so that counter-propagating light beams follow a closed path such as a triangle or square (Fig. 1). Alternatively fiber optics can be employed to guide the light through a closed path (Fig. 2). If the platform on which the ring interferometer is mounted is rotating, the interference fringes are displaced compared to their position when the platform is not rotating. The amount of displacement is proportional to the angular velocity of the rotating platform. The axis of rotation does not have to be inside the enclosed area. The phase shift of the interference fringes is proportional to the platform's angular frequency ω {\displaystyle {\boldsymbol {\omega }}} and is given by a formula originally derived by Sagnac: Δ ϕ ≈ 8 π λ c ω ⋅ A {\displaystyle \Delta \phi \approx {\frac {8\pi }{\lambda c}}{\boldsymbol {\omega }}\cdot \mathbf {A} } where A {\displaystyle \mathbf {A} } is the oriented area of the loop and λ {\displaystyle \lambda } the wavelength of light.
The effect is a consequence of the different times it takes right and left moving light beams to complete a full round trip in the interferometer ring. The difference in travel times, when multiplied by the optical frequency c / λ , {\displaystyle c/\lambda ,} determines the phase difference Δ ϕ . {\displaystyle \Delta \phi .}
The rotation thus measured is an absolute rotation , that is, the platform's rotation with respect to an inertial reference frame .
The Michelson–Morley experiment of 1887 had suggested that the hypothetical luminiferous aether , if it existed, was completely dragged by the Earth . To test this hypothesis, Oliver Lodge in 1897 proposed that a giant ring interferometer be constructed to measure the rotation of the Earth; a similar suggestion was made by Albert Abraham Michelson in 1904. They hoped that with such an interferometer, it would be possible to decide between a stationary aether, versus aethers which are partially or completely dragged by the Earth. That is, if the hypothetical aether were carried along by the Earth (or by the interferometer) the result would be negative, while a stationary aether would give a positive result. [ 3 ] [ 4 ] [ 5 ]
The first description of the Sagnac effect in the framework of special relativity was done by Max von Laue in 1911, [ 6 ] [ 7 ] two years before Sagnac conducted his experiment. By continuing the theoretical work of Michelson (1904), von Laue confined himself to an inertial frame of reference (which he called a "valid" reference frame), and in a footnote he wrote "a system which rotates in respect to a valid system K 0 {\displaystyle K^{0}} is not valid". [ 6 ] Assuming constant light speed c {\displaystyle c} , and setting the rotational velocity as ω {\displaystyle \omega } , he computed the propagation time τ + {\displaystyle \tau _{+}} of one ray and τ − {\displaystyle \tau _{-}} of the counter-propagating ray, and consequently obtained the time difference Δ τ = τ + − τ − {\displaystyle \Delta \tau =\tau _{+}-\tau _{-}} . He concluded that this interferometer experiment would indeed produce (when restricted to terms of first order in v / c {\displaystyle v/c} ) the same positive result for both special relativity and the stationary aether (the latter he called "absolute theory" in reference to the 1895-theory of Lorentz ). He also concluded that only complete-aether-drag models (such as the ones of Stokes or Hertz ) would give a negative result. [ 6 ]
The first interferometry experiment aimed at observing the correlation of angular velocity and phase-shift was performed by the French scientist Georges Sagnac in 1913. Its purpose was to detect "the effect of the relative motion of the ether". [ 1 ] [ 2 ] Sagnac believed that his results constituted proof of the existence of a stationary aether. However, as explained above, von Laue already showed in 1911 that this effect is consistent with special relativity. [ 6 ] [ 7 ] Unlike the carefully prepared Michelson–Morley experiment which was set up to prove an aether wind caused by earth drag, the Sagnac experiment could not prove this type of aether wind because a universal aether would affect all parts of the rotating light equally.
Einstein was aware of the phenomenon of the Sagnac effect through the earlier experiments of Franz Harress [ 8 ] in 1911. [ 9 ] Harress' experiment had been aimed at making measurements of the Fresnel drag of light propagating through moving glass. Not aware of the Sagnac effect, Harress had realized the presence of an "unexpected bias" in his measurements, but was unable to explain its cause. [ 10 ] Harress' analysis of the results contained an error, and they were reanalyzed in 1914 by Paul Harzer , who claimed the results were at odds with special relativity. [ 11 ] [ 12 ] This was rebutted by Einstein. [ 13 ] [ 14 ] Harress himself died during the First World War, and his results were not publicly available until von Laue persuaded Otto Knopf, [ 15 ] whose assistant Harress had been, to publish them in 1920. [ 16 ] [ 17 ]
Harress' results were published together with an analysis by von Laue, who showed the role of the Sagnac effect in the experiment. [ 10 ] Laue said that in the Harress experiment there was a calculable difference in time due to both the dragging of light (which follows from the relativistic velocity addition in moving media , i.e. in moving glass) and "the fact that every part of the rotating apparatus runs away from one ray, while it approaches the other one", i.e. the Sagnac effect. He acknowledged that this latter effect alone could cause the time variance and, therefore, "the accelerations connected with the rotation in no way influence the speed of light". [ 10 ]
While Laue's explanation is based on inertial frames, Paul Langevin (1921, 1937) and others described the same effect when viewed from rotating reference frames (in both special and general relativity, see Born coordinates ). So when the Sagnac effect should be described from the viewpoint of a corotating frame, one can use ordinary rotating cylindrical coordinates and apply them to the Minkowski metric , which results into the so-called Born metric or Langevin metric. [ 18 ] [ 19 ] [ 20 ] From these coordinates, one can derive the different arrival times of counter-propagating rays, an effect which was shown by Paul Langevin (1921). [ 21 ] Or when these coordinates are used to compute the global speed of light in rotating frames, different apparent light speeds are derived depending on the orientation, an effect which was shown by Langevin in another paper (1937). [ 22 ]
This does not contradict special relativity and the above explanation by von Laue that the speed of light is not affected by accelerations. Because this apparent variable light speed in rotating frames only arises if rotating coordinates are used, whereas if the Sagnac effect is described from the viewpoint of an external inertial coordinate frame the speed of light of course remains constant – so the Sagnac effect arises no matter whether one uses inertial coordinates (see the formulas in section § Theories below) or rotating coordinates (see the formulas in section § Reference frames below). That is, special relativity in its original formulation was adapted to inertial coordinate frames, not rotating frames. Albert Einstein in his paper introducing special relativity stated, "light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body". [ 23 ] Einstein specifically stated that light speed is only constant in the vacuum of empty space, using equations that only held in linear and parallel inertial frames. However, when Einstein started to investigate accelerated reference frames, he noticed that "the principle of the constancy of light must be modified" for accelerating frames of reference. [ 24 ]
Max von Laue in his 1920 paper gave serious consideration to the effect of General Relativity on the Sagnac effect stating, "General relativity would of course be capable of giving some statements about it, and we want to show at first that no noticeable influences of acceleration are expected according to it." He makes a footnote regarding discussions with German physicist, Wilhelm Wien . [ 10 ] The reason for looking at General Relativity is because Einstein's Theory of General Relativity predicted that light would slow down in a gravitational field which is why it could predict the curvature of light around a massive body. Under General Relativity, there is the equivalence principle which states that gravity and acceleration are equivalent. Spinning or accelerating an interferometer creates a gravitational effect. "There are, however, two different types of such [non-inertial] motion; it may for instance be acceleration in a straight line, or circular motion with constant speed." [ 25 ] Also, Irwin Shapiro in 1964 explained General Relativity saying, "the speed of a light wave depends on the strength of the gravitational potential along its path". This is called the Shapiro delay . [ 26 ] However, since the gravitational field would have to be significant, Laue (1920) concluded it is more likely that the effect is a result of changing the distance of the path by its movement through space. [ 10 ] "The beam traveling around the loop in the direction of rotation will have farther to go than the beam traveling counter to the direction of rotation, because during the period of travel the mirrors and detector will all move (slightly) toward the counter-rotating beam and away from the co-rotating beam. Consequently the beams will reach the detector at slightly different times, and slightly out of phase, producing optical interference 'fringes' that can be observed and measured." [ 27 ]
In 1926, an ambitious ring interferometry experiment was set up by Albert Michelson and Henry Gale . The aim was to find out whether the rotation of the Earth has an effect on the propagation of light in the vicinity of the Earth. The Michelson–Gale–Pearson experiment was a very large ring interferometer, (a perimeter of 1.9 kilometer), large enough to detect the angular velocity of the Earth. The outcome of the experiment was that the angular velocity of the Earth as measured by astronomy was confirmed to within measuring accuracy. The ring interferometer of the Michelson–Gale experiment was not calibrated by comparison with an outside reference (which was not possible, because the setup was fixed to the Earth). From its design it could be deduced where the central interference fringe ought to be if there would be zero shift. The measured shift was 230 parts in 1000, with an accuracy of 5 parts in 1000. The predicted shift was 237 parts in 1000. [ 28 ]
The Sagnac effect has stimulated a century long debate on its meaning and interpretation, [ 29 ] [ 30 ] [ 31 ] much of this debate being surprising since the effect is perfectly well understood in the context of special relativity.
The shift in interference fringes in a ring interferometer can be viewed intuitively as a consequence of the different distances that light travels due to the rotation of the ring.(Fig. 3) [ 32 ] The simplest derivation is for a circular ring of radius R, with a refractive index of one, rotating at an angular velocity of ω {\displaystyle \omega } , but the result is general for loop geometries with other shapes. If a light source emits in both directions from one point on the rotating ring, light traveling in the same direction as the rotation direction needs to travel more than one circumference around the ring before it catches up with the light source from behind. The time t 1 {\displaystyle t_{1}} that it takes to catch up with the light source is given by:
Δ L {\displaystyle \Delta L} is the distance (black bold arrow in Fig. 3) that the mirror has moved in that same time:
Eliminating Δ L {\displaystyle \Delta L} from the two equations above we get:
Likewise, the light traveling in the opposite direction of the rotation will travel less than one circumference before hitting the light source on the front side. So the time for this direction of light to reach the moving source again is:
The time difference is
For R ω = v ≪ c {\displaystyle R\omega =v\ll c} , this reduces to
where A is the area of the ring.
Although this simple derivation is for a circular ring with an index of refraction of one, the result holds true for any shape of rotating loop with area A .(Fig. 4)
For more complicated shapes, or other refractive index values, the same result can be derived by calculating the optical phase shift in each direction using Fermat's principle and taking into account the different phase velocities for the different propagation directions in an inertial laboratory frame, which can be calculated using relativistic addition of velocities. [ 33 ]
We imagine a screen for viewing fringes placed at the light source (or we use a beamsplitter to send light from the source point to the screen). Given a steady light source, interference fringes will form on the screen with a fringe displacement proportional to the time differences required for the two counter-rotating beams to traverse the circuit. The phase shift is Δ ϕ = 2 π c Δ t λ {\displaystyle \Delta \phi ={\frac {2\pi c\,\Delta t}{\lambda }}} , which causes fringes to shift in proportion to A {\displaystyle A} and ω {\displaystyle \omega } .
At non-relativistic speeds, the Sagnac effect is a simple consequence of the source independence of the speed of light. In other words, the Sagnac experiment does not distinguish between pre-relativistic physics and relativistic physics. [ 32 ]
When light propagates in fibre optic cable, the setup is effectively a combination of a Sagnac experiment and the Fizeau experiment . In glass the speed of light is slower than in vacuum, and the optical cable is the moving medium. In that case the relativistic velocity addition rule applies. Pre-relativistic theories of light propagation cannot account for the Fizeau effect. (By 1900 Lorentz could account for the Fizeau effect, but by that time his theory had evolved to a form where in effect it was mathematically equivalent to special relativity.)
Since emitter and detector are traveling at the same speeds, Doppler effects cancel out, so the Sagnac effect does not involve the Doppler effect. In the case of ring laser interferometry, it is important to be aware of this. When the ring laser setup is rotating, the counterpropagating beams undergo frequency shifts in opposite directions. This frequency shift is not a Doppler shift, but is rather an optical cavity resonance effect, as explained below in Ring lasers .
The Sagnac effect is well understood in the context of special relativity where from the rotating light source's point of view the phase difference is due to the line of simultaneity along the light path not forming a closed loop in spacetime. [ 34 ]
Modified versions of the experiment have been proposed [ 35 ] with the light source allowed to move along a (not necessarily circular) light path. This configuration introduces another reason for the phase difference: according to the light source the two signals now follow different paths in space. Some authors refer to this effect as Sagnac effect [ 31 ] [ 36 ] although in this case the discrepancy need not be due to the lines of simultaneity not forming closed loops.
An example of the modified configuration is shown in Fig. 5, the measured phase difference in both a standard fibre optic gyroscope, shown on the left, and a modified fibre optic conveyor, shown on the right, conform to the equation Δ t = 2 vL / c 2 , whose derivation is based on the constant speed of light. It is evident from this formula that the total time delay is equal to the cumulative time delays along the entire length of fibre, regardless whether the fibre is in a rotating section of the conveyor, or a straight section.
This equation is invalid, however, if the light source's path in space does not follow that of the light signals, for example in the standard rotating platform case (FOG) but with a non-circular light path. In this case the phase difference formula necessarily involves the area enclosed by the light path due to Stokes' theorem . [ 34 ]
Consider a ring interferometer where two counter-propagating light beams share a common optical path determined by a loop of an optical fiber, see Figure 4. The loop may have an arbitrary shape, and can move arbitrarily in space. The only restriction is that it is not allowed to stretch. (The case of a circular ring interferometer rotating about its center in free space is recovered by taking the index of refraction of the fiber to be 1.)
Consider a small segment of the fiber, whose length in its rest frame is d ℓ ′ {\displaystyle d\ell '} . The time intervals, d t ± ′ {\displaystyle dt'_{\pm }} , it takes the left and right moving light rays to traverse the segment in the rest frame coincide and are given by d t ± ′ = n c d ℓ ′ {\displaystyle dt'_{\pm }={n \over c}d\ell '} Let d ℓ = | d x | {\textstyle d\ell =|d\mathbf {x} |} be the length of this small segment in the lab frame. By the relativistic length contraction formula, d ℓ ′ = γ d ℓ ≈ d ℓ {\textstyle d\ell '=\gamma d\ell \approx d\ell } correct to first order in the velocity v {\displaystyle \mathbf {v} } of the segment. The time intervals d t ± {\displaystyle dt_{\pm }} for traversing the segment in the lab frame are given by Lorentz transformation as: d t ± = γ ( d t ′ ± v ⋅ d x ′ c 2 ) ≈ n c d ℓ ± v c 2 ⋅ d x {\displaystyle dt_{\pm }=\gamma \left(dt'\pm {\frac {\mathbf {v} \cdot d\mathbf {x} '}{c^{2}}}\right)\approx {\frac {n}{c}}d\ell \pm {\frac {\mathbf {v} }{c^{2}}}\cdot d\mathbf {x} } correct to first order in the velocity v {\displaystyle \mathbf {v} } . In general, the two beams will visit a given segment at slightly different times, but, in the absence of stretching, the length d ℓ {\textstyle d\ell } is the same for both beams.
It follows that the time difference for completing a cycle for the two beams is Δ T = ∫ ( d t + − d t − ) ≈ 2 c 2 ∮ v ⋅ d x {\displaystyle \Delta T=\int \left(dt_{+}-dt_{-}\right)\approx {\frac {2}{c^{2}}}\oint \mathbf {v} \cdot d\mathbf {x} } Remarkably, the time difference is independent of the refraction index n {\displaystyle n} and the velocity of light in the fiber.
Imagine a screen for viewing fringes placed at the light source (alternatively, use a beamsplitter to send light from the source point to the screen). Given a steady light source, interference fringes will form on the screen with a fringe displacement given by Δ ϕ ≈ 2 π c λ Δ T {\textstyle \Delta \phi \approx {\frac {2\pi c}{\lambda }}\Delta T} where the first factor is the frequency of light. This gives the generalized Sagnac formula [ 37 ] Δ ϕ ≈ 4 π λ c ∮ v ⋅ d x {\displaystyle \Delta \phi \approx {\frac {4\pi }{\lambda c}}\oint \mathbf {v} \cdot d\mathbf {x} } In the special case that the fiber moves like a rigid body with angular frequency ω {\displaystyle {\boldsymbol {\omega }}} , the velocity is v = ω × x {\textstyle \mathbf {v} ={\boldsymbol {\omega }}\times \mathbf {x} } and the line integral can be computed in terms of the area of the loop: ∮ v ⋅ d x = ∮ ω × x ⋅ d x = ∮ ω ⋅ x × d x = 2 ∮ ω ⋅ d A = 2 ω ⋅ A {\displaystyle \oint \mathbf {v} \cdot d\mathbf {x} =\oint {\boldsymbol {\omega }}\times \mathbf {x} \cdot d\mathbf {x} =\oint {\boldsymbol {\omega }}\cdot \mathbf {x} \times d\mathbf {x} =2\oint {\boldsymbol {\omega }}\cdot d\mathbf {A} =2{\boldsymbol {\omega }}\cdot \mathbf {A} } This gives Sagnac formula for ring interferometers of arbitrary shape and geometry Δ ϕ ≈ 8 π λ c ω ⋅ A {\displaystyle \Delta \phi \approx {\frac {8\pi }{\lambda c}}{\boldsymbol {\omega }}\cdot \mathbf {A} } If one also allows for stretching one recovers the Fizeau interference formula. [ 37 ]
A relay of pulses that circumnavigates the Earth, verifying precise synchronization, is also recognized as a case requiring correction for the Sagnac effect. In 1984 a verification was set up that involved three ground stations and several GPS satellites, with relays of signals both going eastward and westward around the world. [ 38 ] In the case of a Sagnac interferometer a measure of difference in arrival time is obtained by producing interference fringes, and observing the fringe shift. In the case of a relay of pulses around the world the difference in arrival time is obtained directly from the actual arrival time of the pulses. In both cases the mechanism of the difference in arrival time is the same: the Sagnac effect.
The Hafele–Keating experiment is also recognized as a counterpart to Sagnac effect physics. [ 38 ] In the actual Hafele–Keating experiment [ 39 ] the mode of transport (long-distance flights) gave rise to time dilation effects of its own, and calculations were needed to separate the various contributions. For the (theoretical) case of clocks that are transported so slowly that time dilation effects arising from the transport are negligible the amount of time difference between the clocks when they arrive back at the starting point will be equal to the time difference that is found for a relay of pulses that travels around the world: 207 nanoseconds.
The Sagnac effect is employed in current technology. One use is in inertial guidance systems . Ring laser gyroscopes are extremely sensitive to rotations, which need to be accounted for if an inertial guidance system is to return accurate results. The ring laser also can detect the sidereal day , which can also be termed "mode 1".
Global navigation satellite systems (GNSSs) – such as GPS , GLONASS , COMPASS or Galileo – need to take the rotation of the Earth into account in the procedures of using radio signals to synchronize clocks. [ 40 ]
Fibre optic gyroscopes are sometimes referred to as 'passive ring interferometers'. A passive ring interferometer uses light entering the setup from outside. The interference pattern that is obtained is a fringe pattern, and what is measured is a phase shift.
It is also possible to construct a ring interferometer that is self-contained, based on a completely different arrangement. This is called a ring laser or ring laser gyroscope . The light is generated and sustained by incorporating laser excitation in the path of the light.
To understand what happens in a ring laser cavity, it is helpful to discuss the physics of the laser process in a laser setup with continuous generation of light. As the laser excitation is started, the molecules inside the cavity emit photons, but since the molecules have a thermal velocity, the light inside the laser cavity is at first a range of frequencies, corresponding to the statistical distribution of velocities. The process of stimulated emission makes one frequency quickly outcompete other frequencies, and after that the light is very close to monochromatic.
For the sake of simplicity, assume that all emitted photons are emitted in a direction parallel to the ring. Fig. 7 illustrates the effect of the ring laser's rotation. In a linear laser, an integer multiple of the wavelength fits the length of the laser cavity. This means that in traveling back and forth the laser light goes through an integer number of cycles of its frequency. In the case of a ring laser the same applies: the number of cycles of the laser light's frequency is the same in both directions. This quality of the same number of cycles in both directions is preserved when the ring laser setup is rotating. The image illustrates that there is wavelength shift (hence a frequency shift) in such a way that the number of cycles is the same in both directions of propagation.
By bringing the two frequencies of laser light to interference a beat frequency can be obtained; the beat frequency is the difference between the two frequencies. This beat frequency can be thought of as an interference pattern in time. (The more familiar interference fringes of interferometry are a spatial pattern). The period of this beat frequency is linearly proportional to the angular velocity of the ring laser with respect to inertial space. This is the principle of the ring laser gyroscope , widely used in modern inertial navigation systems .
In passive ring interferometers, the fringe displacement is proportional to the first derivative of angular position; careful calibration is required to determine the fringe displacement that corresponds to zero angular velocity of the ring interferometer setup. On the other hand, ring laser interferometers do not require calibration to determine the output that corresponds to zero angular velocity. Ring laser interferometers are self-calibrating. The beat frequency will be zero if and only if the ring laser setup is non-rotating with respect to inertial space.
Fig. 8 illustrates the physical property that makes the ring laser interferometer self-calibrating. The grey dots represent molecules in the laser cavity that act as resonators. Along every section of the ring cavity, the speed of light is the same in both directions. When the ring laser device is rotating, then it rotates with respect to that background. In other words: invariance of the speed of light provides the reference for the self-calibrating property of the ring laser interferometer.
Ring laser gyroscopes suffer from an effect known as "lock-in" at low rotation rates (less than 100°/h). At very low rotation rates, the frequencies of the counter-propagating laser modes become almost identical. In this case, crosstalk between the counter-propagating beams can result in injection locking , so that the standing wave "gets stuck" in a preferred phase, locking the frequency of each beam to each other rather than responding to gradual rotation. By rotationally dithering the laser cavity back and forth through a small angle at a rapid rate (hundreds of hertz ), lock-in will only occur during the brief instances where the rotational velocity is close to zero; the errors thereby induced approximately cancel each other between alternating dead periods.
Fibre optic gyros (FOGs) and ring laser gyros (RLGs) both operate by monitoring the difference in propagation time between beams of light traveling in clockwise and counterclockwise directions about a closed optical path. They differ considerably in various cost, reliability, size, weight, power, and other performance characteristics that need to be considered when evaluating these distinct technologies for a particular application.
RLGs require accurate machining, use of precision mirrors, and assembly under clean room conditions. Their mechanical dithering assemblies add somewhat to their weight but not appreciably. [ citation needed ] RLGs are capable of logging in excess of 100,000 hours of operation in near-room temperature conditions. [ citation needed ] Their lasers have relatively high power requirements. [ 41 ]
Interferometric FOGs are purely solid-state, require no mechanical dithering components, do not require precision machining, have a flexible geometry, and can be made very small. They use many standard components from the telecom industry. In addition, the major optical components of FOGs have proven performance in the telecom industry, with lifespans measured in decades. [ 42 ] However, the assembly of multiple optical components into a precision gyro instrument is costly. Analog FOGs offer the lowest possible cost but are limited in performance; digital FOGs offer the wide dynamic ranges and accurate scale factor corrections required for stringent applications. [ 43 ] Use of longer and larger coils increases sensitivity at the cost of greater sensitivity to temperature variations and vibrations.
The Sagnac topology was actually first described by Michelson in 1886, [ 44 ] who employed an even-reflection variant of this interferometer in a repetition of the Fizeau experiment . [ 45 ] Michelson noted the extreme stability of the fringes produced by this form of interferometer: White-light fringes were observed immediately upon alignment of the mirrors. In dual-path interferometers, white-light fringes are difficult to obtain since the two path lengths must be matched to within a couple of micrometers (the coherence length of the white light). However, being a common-path interferometer , the Sagnac configuration inherently matches the two path lengths. Likewise Michelson observed that the fringe pattern would remain stable even while holding a lighted match below the optical path; in most interferometers the fringes would shift wildly due to the refractive index fluctuations from the warm air above the match. Sagnac interferometers are almost completely insensitive to displacements of the mirrors or beam-splitter. [ 46 ] This characteristic of the Sagnac topology has led to their use in applications requiring exceptionally high stability.
The fringe shift in a Sagnac interferometer due to rotation has a magnitude proportional to the enclosed area of the light path, and this area must be specified in relation to the axis of rotation. Thus the sign of the area of a loop is reversed when the loop is wound in the opposite direction (clockwise or anti-clockwise). A light path that includes loops in both directions, therefore, has a net area given by the difference between the areas of the clockwise and anti-clockwise loops. The special case of two equal but opposite loops is called a zero-area Sagnac interferometer. The result is an interferometer that exhibits the stability of the Sagnac topology while being insensitive to rotation. [ 47 ]
The Laser Interferometer Gravitational-Wave Observatory (LIGO) consisted of two 4-km Michelson–Fabry–Pérot interferometers , and operated at a power level of about 100 watts of laser power at the beam splitter. After an upgrade to Advanced LIGO several kilowatts of laser power are required.
A variety of competing optical systems are being explored for third generation enhancements beyond Advanced LIGO. [ 48 ] One of these competing proposals is based on the zero-area Sagnac design. With a light path consisting of two loops of the same area, but in opposite directions, an effective area of zero is obtained thus canceling the Sagnac effect in its usual sense. Although insensitive to low frequency mirror drift, laser frequency variation, reflectivity imbalance between the arms, and thermally induced birefringence, this configuration is nevertheless sensitive to passing gravitational waves at frequencies of astronomical interest. [ 47 ] However, many considerations are involved in the choice of an optical system, and despite the zero-area Sagnac's superiority in certain areas, there is as yet no consensus choice of optical system for third generation LIGO. [ 49 ] [ 50 ] | https://en.wikipedia.org/wiki/Sagnac_effect |
The Sahara Forest Project aims to provide fresh water, food and renewable energy in hot, arid regions as well as re-vegetating areas of uninhabited desert . [ 1 ] [ 2 ] The founding team was composed of Seawater Greenhouse Ltd, Exploration Architecture, Max Fordham Consulting Engineers and the Bellona Foundation .
The proposed technology combines saltwater-cooled greenhouses with solar power technologies, either directly using photovoltaic (PV) or indirectly using concentrated solar power and technologies for desert revegetation. It is claimed that these technologies together will create a sustainable and profitable source of energy, food, vegetation and water. The scale of the proposed project is such that very large quantities of seawater would be evaporated. By using locations below sea level , pumping costs would be eliminated. A project in Qatar has been completed, and pilot projects in Jordan and Tunisia have been initiated. [ 3 ] [ 4 ] [ 5 ] [ 6 ]
Sahara Forest Project's first pilot facility was built in Qatar and officially opened on 16 December 2012 by the then Heir Apparent Sheikh Tamim bin Hamad Al Thani . [ 7 ] [ 4 ] [ 5 ] [ 6 ] The results were better than expected. [ 8 ] [ 9 ] The results have guided next steps, namely a test and demonstration center providing the first commercial-scale of the full Sahara Forest Project value chain.
On 22 June 2014, the Sahara Forest Project signed an agreement with the Norwegian Embassy in Amman for establishing a Sahara Forest Project Launch Station and related activities in Jordan . [ 10 ] The Launch Station will be the first step towards a full-scale Sahara Forest Project Centre in Aqaba , Jordan. The Launch Station will contain a saltwater-cooled greenhouse in combination with solar power technologies and facilities for outdoor cultivation and revegetation. The Qatar plant was dismantled in 2016, and is expected to be operational in Jordan in 2017 after being shipped. [ 11 ]
Not all reports on the project are optimistic. Hydroponics projects globally tend to be overly optimistic but there are downsides to producing expensive crops in a population that cannot afford to buy them. [ 12 ] | https://en.wikipedia.org/wiki/Sahara_Forest_Project |
The Sahara Sea was the name of a hypothetical macro-engineering project which proposed flooding endorheic basins in the Sahara with waters from the Atlantic Ocean or Mediterranean Sea . The goal of this unrealised project was to create an inland sea that would cover the substantial areas of the Sahara which lie below sea level , bringing humid air, rain, and agriculture deep into the desert.
The possibility of such a project was raised several times by different scientists and engineers during the late 19th century and early 20th century. The concept of a flooded Sahara was also featured in novels of the time. [ 1 ]
In 1877 the Scottish entrepreneur and abolitionist Donald Mackenzie was the first to propose the creation of a Sahara Sea. Mackenzie's idea was to cut a channel from one of the sand-barred lagoons north of Cape Juby , south to a large plain which Arab traders had identified to him as El Djouf . [ 2 ] [ 3 ] Mackenzie believed this vast region was up to 61 metres (200 ft) below sea level and that flooding it would create an inland sea of 155,400 square kilometres (60,000 sq mi) suited to commercial navigation and even agriculture. He further believed that geological evidence suggested this basin had once been connected to the Atlantic via a channel near the Saguia el-Hamra . He proposed that this inland sea, if augmented with a canal, could provide access to the Niger River and the markets and rich resources of West Africa. [ 3 ]
There are several small depressions in the vicinity of Cape Juby; at 55 m below sea level, the Sebkha Tah [ 4 ] is the lowest and largest. But it covers less than 250 km² and is 500 km north of the geographical area identified as El Djouf (also known as the Majabat al-Koubra [ 5 ] ) which has an average elevation of 320m.
Mackenzie never travelled in this area but had read of other sub-sea level desert basins in present-day Tunisia , Algeria , and Egypt similar to those found near Cape Juby. [ 3 ] These basins contain seasonally dry salt lakes , known as chotts or sebkhas .
François Elie Roudaire , a French geographer, and Ferdinand de Lesseps , a diplomat influential in the creation of the Suez Canal , proposed this area for the creation of an inland sea in 1878. Roudaire and de Lesseps proposed that a channel be cut from the Gulf of Gabès in the Mediterranean to the Chott el Fejej [ 6 ] which would allow the sea to drain into these basins. They were not specific in the area such a sea would cover (although subsequent analyses suggested that it would be considerably smaller than Mackenzie's proposal at only 8,000 square kilometres (3,100 sq mi) in area), but argued that the new inland sea would improve the quality of weather on the European continent. [ 7 ] [ 8 ] [ 9 ] The estimated cost of the Roudaire project was $30,000,000 at the time. [ 9 ]
While Roudaire and de Lesseps were optimistic about the weather effects that such an inland sea would produce in Europe, others were not as hopeful. Alexander William Mitchinson argued that flooding substantial areas would create disease-ridden swamps. [ 7 ] [ 10 ] Others were critical of the feasibility of the project or the proposal to join the sea at El Djouf with the sea in what is now Tunisia and Algeria. [ 7 ] The project was ultimately rejected by the French Government and funding was withdrawn when surveys revealed that many areas were not below sea level as had been believed. [ 8 ] [ 11 ]
The proposal to create a Sahara Sea was revived in the early 1900s by French professor Edmund Etchegoyen . Around 1910, Etchegoyen proposed that a longer and deeper channel could be constructed. He argued that such a sea could be a boon for colonisation and could potentially produce an inland sea half the size of the Mediterranean. [ 12 ] This proposal was considered by the French government but also rejected. Critics noted that, while some parts of the Sahara were indeed below sea level, much of the Sahara was above sea level. This, they said, would produce an irregular sea of bays and coves; it would also be considerably smaller than estimates by Etchegoyen suggested. [ 7 ]
A proposal similar to that of Roudaire and de Lesseps was raised by members of Operation Plowshare , an American idea to use nuclear explosives in civil engineering projects such as the Qattara Depression Project . [ 13 ]
It was also suggested that nuclear explosives might be detonated to create a channel from the Mediterranean to the chotts of Tunisia. [ 11 ] [ 14 ] This proposal was abandoned, [ 11 ] however, with the signing of various treaties prohibiting peaceful nuclear explosions . [ 13 ]
The project regained steam in the mid 2010s with the creation of the association Cooperation Road [ 15 ] which in 2018 obtained the approval of the Tunisian government. [ 16 ]
The notion of a Sahara Sea has been featured several times in literature, most notably in Jules Verne 's last novel, Invasion of the Sea , which directly referred to the plan of Roudaire and de Lesseps. [ 1 ] The idea of a flooded Sahara also occurs in The Secret People by John Wyndham .
In the 2018 film Aquaman , the Sahara was once a sea inhabited by an Atlantean tribe.
Since the late 19th century there have been proposals to connect Lake Eyre in the South Australian desert to the ocean via canal. [ 17 ]
In 1905, engineers working on an irrigation canal in southern California accidentally released the waters of the Colorado River into a formerly dry basin, creating a large saline lake known as the Salton Sea . Although the lake has shrunk considerably since its creation, it remains the largest lake in the state of California. | https://en.wikipedia.org/wiki/Sahara_Sea |
Sahati Suharto (10 March 1932 – 14 April 2020) was an Indonesian chemist and academic administrator from the University of Indonesia who became the dean of the university's Faculty of Math and Natural Sciences from 1984 to 1988.
Born on 10 March 1932 in Jakarta, [ 1 ] Sahati received her bachelor's degree in chemistry from the Bandung Institute of Technology in 1963. [ 2 ] Sahati taught inorganic chemistry at the university and translated several textbooks on the subject. She was appointed as the chair of the chemistry department from 1975 until 1976. Around November 1976, Sahati conducted a two-week trip to Japan, where she visited universities and chemical facilities. [ 3 ] Two years later, she was appointed by dean of the Faculty of Exact Sciences and Natural Sciences Soekarja Somadikarta to serve as his deputy for academic, research, and community service. [ 4 ] She served in this position until 19 November 1984. [ 1 ]
On 19 November 1984, Sahati became the dean of University of Indonesia's Faculty of Math and Natural Science. [ 4 ] She was the second woman to hold this position. [ 1 ] During her tenure, she was sued by one of her students, whom she expelled due to bad grades. Sahati had previously offered him a chance to re-apply but was refused. [ 5 ] She served in the position until she was replaced by Parangtopo Sutokusumo on 1 March 1988. [ 6 ] Sahati continued teaching chemistry at the university until her retirement and supported efforts to introduce chemistry to high school students, urging students not to fear chemistry. [ 7 ]
Sahati died on 14 April 2020 at her residence in Bandung, West Java. [ 1 ] | https://en.wikipedia.org/wiki/Sahati_Suharto |
SahysMod is a computer program for the prediction of the salinity of soil moisture, groundwater and drainage water, the depth of the watertable , and the drain discharge in irrigated agricultural lands, using different hydrogeologic and aquifer conditions, varying water management options, including the use of ground water for irrigation, and several crop rotation schedules, whereby the spatial variations are accounted for through a network of polygons. [ 1 ]
There is a need for a computer program that is easier to operate and that requires a simpler data structure then most currently available models. Therefore, the SahysMod program was designed keeping in mind a relative simplicity of operation to facilitate the use by field technicians, engineers and project planners instead of specialized geo-hydrologists . It aims at using input data that are generally available, or that can be estimated with reasonable accuracy, or that can be measured with relative ease. Although the calculations are done numerically and have to be repeated many times, the final results can be checked by hand using the formulas in this manual. [ 2 ]
SahysMod's objective is to predict the long-term hydro- salinity in terms of general trends , not to arrive at exact predictions of how, for example, the situation would be on the first of April in ten years from now. Further, SahysMod gives the option of the re-use of drainage and well water (e.g. for irrigation ) and it can account for farmers ' responses to waterlogging , soil salinity , water scarcity and over-pumping from the aquifer . Also it offers the possibility to introduce subsurface drainage systems at varying depths and with varying capacities so that they can be optimized .
Other features of SahysMod are found in the next section.
The model calculates the ground water levels and the incoming and outgoing ground water flows between the polygons by a numerical solution of the well-known Boussinesq equation . The levels and flows influence each other mutually.
The ground water situation is further determined by the vertical groundwater recharge that is calculated from the agronomic water balance . These depend again on the levels of the ground water .
When semi-confined aquifers are present, the resistance to vertical flow in the slowly permeable top-layer and the overpressure in the aquifer, if any, are taken into account. [ 3 ]
Hydraulic boundary conditions are given as hydraulic heads in the external nodes in combination with the hydraulic conductivity between internal and external nodes. If one wishes to impose a zero flow condition at the external nodes, the conductivity can be set at zero.
Further, aquifer flow conditions can be given for the internal nodes. These are required when a geological fault is present at the bottom of the aquifer or when flow occurs between the main aquifer and a deeper aquifer separated by a semi-confining layer.
The depth of the water table , the rainfall and salt concentrations of the deeper layers are assumed to be the same over the whole polygon. Other parameters can very within the polygons according to type of crops and cropping rotation schedule.
The model is based on seasonal input data and returns seasonal outputs. The number of seasons per year can be chosen between a minimum of one and a maximum of four. One can distinguish for example dry, wet, cold, hot, irrigation or fallow seasons. Reasons of not using smaller input/output periods are:
Many water balance factors depend on the level of the water table , which again depends on some of the water-balance factors. Due to these mutual influences there can be non-linear changes throughout the season. Therefore, the computer program performs daily calculations. For this purpose, the seasonal water-balance factors given with the inpu] are reduced automatically to daily values. The calculated seasonal water-balance factors, as given in the output, are obtained by summations of the daily calculated values. Groundwater levels and soil salinity (the state variables ) at the end of the season are found by accumulating the daily changes of water and salt storage.
In some cases the program may detect that the time step must be taken less than 1 day for better accuracy. The necessary adjustments are made automatically. [ 5 ]
The model permits a maximum of 240 internal and 120 external polygons with a minimum of 3 and a maximum of 6 sides each. The subdivision of the area into polygons, based on nodal points with known coordinates , should be governed by the characteristics of the distribution of the cropping , irrigation , drainage and groundwater characteristics over the study area.
The nodes must be numbered, which can be done at will. With an index one indicates whether the node is internal or external. Nodes can be added and removed at will or changed from internal to external or vice versa. Through another index one indicates whether the internal nodes have an unconfined or semi-confined aquifer. This can also be changed at will.
Nodal network relations are to be given indicating the neighboring polygon numbers of each node. The program then calculates the surface area of each polygon, the distance between the nodes and the length of the sides between them using the Thiessen principle.
The hydraulic conductivity can vary for each side of the polygons.
The depth of the water table , the rainfall and salt concentrations of the deeper layers are assumed to be the same over the whole polygon. Other parameters can very within the polygons according to type of crops and cropping rotation schedule. [ 6 ]
The method uses seasonal water balance components as input data. These are related to the surface hydrology (like rainfall, potential evaporation , irrigation , use of drain and well water for irrigation, runoff ), and the aquifer hydrology (e.g., pumping from wells ). The other water balance components (like actual evaporation, downward percolation , upward capillary rise , subsurface drainage , groundwater flow ) are given as output.
The quantity of drainage water, as output, is determined by two drainage intensity factors for drainage above and below drain level respectively (to be given with the input data) and the height of the water table above the given drain level. This height results from the computed water balance Further, a drainage reduction factor can be applied to simulate a limited operation of the drainage system. Variation of the drainage intensity factors and the drainage reduction factor gives the opportunity to simulate the effect of different drainage options.
To obtain accuracy in the computations of the ground water flow (sect. 2.8), the actual evaporation and the capillary rise, the computer calculations are done on a daily basis. For this purpose, the seasonal hydrological data are divided by the number of days per season to obtain daily values. The daily values are added to yield seasonal values. [ 7 ]
The input data on irrigation, evaporation, and surface runoff are to be specified per season for three kinds of agricultural practices, which can be chosen at the discretion of the user:
The groups, expressed in fractions of the total area, may consist of combinations of crops or just of a single kind of crop. For example, as the A-type crops one may specify the lightly irrigated cultures, and as the B type the more heavily irrigated ones, such as sugarcane and rice . But one can also take A as rice and B as sugar cane, or perhaps trees and orchards . A, B and/or U crops can be taken differently in different seasons, e.g. A= wheat plus barley in winter and A= maize in summer while B= vegetables in winter and B= cotton in summer. Non-irrigated land can be specified in two ways: (1) as U = 1−A−B and (2) as A and/or B with zero irrigation. A combination can also be made.
Further, a specification must be given of the seasonal rotation of the different land uses over the total area, e.g. full rotation, no rotation at all, or incomplete rotation. This occurs with a rotation index. The rotations are taken over the seasons within the year. To obtain rotations over the years it is advisable to introduce annual input changes as explained
When a fraction A1, B1 and/or U1 differs from the fraction A2, B2 and/or U2 in another season, because the irrigation regime changes in the different seasons, the program will detect that a certain rotation occurs. If one wishes to avoid this, one may specify the same fractions in all seasons (A2=A1, B2=B1, U2=U1) but the crops and irrigation quantities may be different and may need to be proportionally adjusted. One may even specify irrigated land (A or B) with zero irrigation, which is the same as un-irrigated land (U).
Cropping rotation schedules vary widely in different parts of the world. Creative combinations of area fractions, rotation indexes, irrigation quantities and annual input changes can accommodate many types of agricultural practices. [ 8 ]
Variation of the area fractions and/or the rotational schedule gives the opportunity to simulate the effect of different agricultural practices on the water and salt balance. [ 9 ]
SahysMod accepts four different reservoirs of which three are in the soil profile:
The upper soil reservoir is defined by the soil depth, from which water can evaporate or be taken up by plant roots. It can be taken equal to the root zone. It can be saturated, unsaturated, or partly saturated, depending on the water balance. All water movements in this zone are vertical, either upward or downward, depending on the water balance. (In a future version of Sahysmod, the upper soil reservoir may be divided into two equal parts to detect the trend in the vertical salinity distribution.)
The transition zone can also be saturated, unsaturated or partly saturated. All flows in this zone are horizontal, except the flow to subsurface drains, which is radial.
If a horizontal subsurface drainage system is present, this must be placed in the transition zone, which is then divided into two parts: an upper transition zone (above drain level) and a lower transition zone (below drain level).
If one wishes to distinguish an upper and lower part of the transition zone in the absence of a subsurface drainage system, one may specify in the input data a drainage system with zero intensity. [ 10 ]
The aquifer has mainly horizontal flow. Pumped wells , if present, receive their water from the aquifer only. The flow in the aquifer is determined in dependence of spatially varying depths of the aquifer, levels of the water table, and hydraulic conductivity .
SahysMod permits the introduction of phreatic ( unconfined ) and semi-confined aquifers. The latter may develop a hydraulic over or under pressure below the slowly permeable top-layer ( aquitard ).
The agricultural water balances are calculated for each soil reservoir separately as shown in the article Hydrology (agriculture) . The excess water leaving one reservoir is converted into incoming water for the next reservoir. The three soil reservoirs can be assigned different thickness and storage coefficients, to be given as input data. When, in a particular situation the transition zone or the aquifer is not present, they must be given a minimum thickness of 0.1 m.
The depth of the water table at the end of the previous time step, calculated from the water balances , is assumed to be the same within each polygon . If this assumption is not acceptable, the area must be divided into a larger number of polygons.
Under certain conditions, the height of the water table influences the water-balance components. For example, a rise of the water table towards the soil surface may lead to an increase of capillary rise, actual evaporation, and subsurface drainage, or a decrease of percolation losses. This, in turn, leads to a change of the water-balance, which again influences the height of the water table, etc. This chain of reactions is one of the reasons why Sahysmod has been developed into a computer program , in which the computations are made day by day to account for the chain of reactions with a sufficient degree of accuracy .
The sub-surface drainage can be accomplished through drains or pumped wells.
The subsurface drains, if any, are characterized by drain depth and drainage capacity . The drains are located in the transition zone. The subsurface drainage facility can be applied to natural or artificial drainage systems. The functioning of an artificial drainage system can be regulated through a drainage control factor.
By installing a drainage system with zero capacity one obtains the opportunity to have separate water and salt balances in the transition above and below drain level.
The pumped wells , if any, are located in the aquifer. Their functioning is characterized by the well discharge .
The drain and well water can be used for irrigation through a (re)use factor . This may affect the water and salt balance and on the irrigation efficiency or sufficiency.
The salt balances are calculated for each soil reservoir separately. They are based on their water balances , using the salt concentrations of the incoming and outgoing water. Some concentrations must be given as input data, like the initial salt concentrations of the water in the different soil reservoirs, of the irrigation water and of the incoming groundwater in the aquifer. The concentrations are expressed in terms of electric conductivity (EC in dS/m). When the concentrations are known in terms of g salt/L water, the rule of thumb: 1 g/L -> 1.7 dS/m can be used. Usually, salt concentrations of the soil are expressed in ECe, the electric conductivity of an extract of a saturated soil paste. In Sahysmod, the salt concentration is expressed as the EC of the soil moisture when saturated under field conditions. As a rule, one can use the conversion rate EC : ECe = 2 : 1. The principles used are correspond to those described in the article soil salinity control .
Salt concentrations of outgoing water (either from one reservoir into the other or by subsurface drainage) are computed on the basis of salt balances, using different leaching or salt mixing efficiencies to be given with the input data. The effects of different leaching efficiencies can be simulated varying their input value.
If drain or well water is used for irrigation, the method computes the salt concentration of the mixed irrigation water in the course of the time and the subsequent effect on the soil and ground water salinity, which again influences the salt concentration of the drain and well water. By varying the fraction of used drain or well water (through the input), the long-term effect of different fractions can be simulated.
The dissolution of solid soil minerals or the chemical precipitation of poorly soluble salts is not included in the computation method. However, but to some extent, it can be accounted for through the input data, e.g. increasing or decreasing the salt concentration of the irrigation water or of the incoming water in the aquifer . In a future version, the precipitation of gypsum may be introduced.
If required, farmers' responses to waterlogging and soil salinity can be automatically accounted for. The method can gradually decrease:
The farmers' responses influence the water and salt balances, which, in turn, slows down the process of water logging and salinization. Ultimately a new equilibrium situation will arise.
The user can also introduce farmers' responses by manually changing the relevant input data. Perhaps it will be useful first to study the automatic farmers' responses and their effect first and thereafter decide what the farmers' responses will be in the view of the user.
The program runs either with fixed input data for the number of years determined by the user. This option can be used to predict future developments based on long-term average input values, e.g. rainfall, as it will be difficult to assess the future values of the input data year by year.
The program also offers the possibility to follow historic records with annually changing input values (e.g. rainfall, irrigation, cropping rotations), the calculations must be made year by year. If this possibility is chosen, the program creates a transfer file by which the final conditions of the previous year (e.g. water table and salinity) are automatically used as the initial conditions for the subsequent period. This facility makes it also possible to use various generated rainfall sequences drawn randomly from a known rainfall probability distribution and to obtain a stochastic prediction of the resulting output parameters.
Some input parameters should not be changed, like the nodal network relations, the system geometry , the thickness of the soil layers, and the total porosity , otherwise illogical jumps occur in the water and salt balances. These parameters are also stored in the transfer file, so that any impermissible change is overruled by the transfer data. In some cases of incorrect changes, the program will stop and request the user to adjust the input. [ 11 ]
The output is given for each season of any year during any number of years, as specified with the input data. The output data comprise hydrological and salinity aspects. As the soil salinity is very variable from place to place (figure left) SahysMod includes frequency distributions in the output. The figure was made with the CumFreq program. [ 12 ] [ 13 ] The output data are filed in the form of tables that can be inspected directly, through the user menu, that calls selected groups of data either for a certain polygon over time, or for a certain season over the polygons. The model includes mapping facilities of output data. Also, the program has the facility to store the selected data in a spreadsheet format for further analysis and for import into a GIS program. Different users may wish to establish different cause-effect relationships. The program offers only a limited number of standard graphics , as it is not possible to foresee all different uses that may be made. This is the reason why the possibility for further analysis through spreadsheet programs was created. Although the computations need many iterations , all the results can be checked by hand using the equations presented in the manual. [ 14 ] | https://en.wikipedia.org/wiki/SahysMod |
Saiful Islam (born 14 August 1963) is a British chemist and professor of materials modelling at the Department of Materials, University of Oxford . Saiful is a Fellow of the Royal Society of Chemistry (FRSC), and received the Royal Society 's Wolfson Research Merit Award and Hughes Medal , and the American Chemical Society Award for Energy Chemistry for his major contributions to the fundamental atomistic understanding of new materials for lithium batteries and perovskite solar cells .
Saiful is an atheist [ 1 ] who refused the Order of the British Empire citing discomfort with the phrase " British Empire " and its link to colonialism. [ 2 ]
Saiful was born in 1963 in Karachi , Pakistan to ethnically Bengali parents. [ 3 ] The family moved to London in 1964 and he grew up in Crouch End , north London. There he went to Stationers' Company's School , a state comprehensive. He received both a BSc degree in chemistry and a PhD (1988) from University College London , where he studied under Professor Richard Catlow . Subsequently, he held a postdoctoral fellowship at the Eastman Kodak laboratories in Rochester, New York , working on oxide superconductors . [ 4 ]
Saiful returned to the UK in 1990 to become a lecturer, then reader, at the University of Surrey . In January 2006 he was appointed professor of Materials Chemistry at the University of Bath. [ 5 ] [ 6 ] His group applies computational methods combined with structural techniques to study fundamental atomistic properties such as ion conduction, defect chemistry and surface structures. [ 7 ] [ 8 ] In January 2022, he joined the Department of Materials, University of Oxford as a professor of materials modelling . [ 9 ]
Saiful has been a member of the editorial board of the Journal of Materials Chemistry , and sits on the advisory board of the RSC journal Energy and Environmental Science . [ 10 ] He is Principal Investigator of the Faraday Institution 's 'CATMAT' project on Next-generation Lithium-Ion Cathode Materials. [ 11 ]
Saiful presented the 2016 Royal Institution Christmas Lectures , entitled "Supercharged: Fuelling the Future" on the theme of energy , a commemorative lecture series for the BBC which celebrated 80 years since the Christmas Lectures [ 12 ] were first broadcast on television in 1936. [ 13 ] The lectures were broadcast on BBC Four , and achieved over 3.5 million interactions through the BBC broadcasts and social media. Saiful was interviewed before these lectures for articles in The Guardian . [ 14 ] [ 15 ] [ 16 ] A demonstration in these lectures led to a Guinness World Record for the highest voltage (1,275 Volts) produced by a fruit battery using more than 1,000 lemons. [ 17 ] Saiful later broke that record in 2021 after using 2,923 lemons to produce 2,307.8 Volts. [ 18 ]
Saiful has served on the Diversity Committee of the Royal Society , and was selected for the Royal Society's 'Inspiring Scientists' [ 19 ] project that recorded the life stories of British scientists with minority ethnic heritage in partnership with National Life Stories at the British Library . His outreach activities include talks on energy materials to student audiences using 3D glasses organised by the TTP Education in Action at the UCL Institute of Education, London. [ 20 ] He was interviewed for The Life Scientific programme on BBC Radio 4 in October 2019. [ 21 ]
On 23 November 2022, Saiful was an invited speaker at the Brian Cox & Robin Ince 's Compendium of Reason charity event, which was at the Royal Albert Hall . [ 22 ] [ 23 ]
As of 2021, Saiful lives in Bath with his wife, Gita Sunthankar (a local GP), and their two children, Yasmin and Zak. [ 24 ]
Saiful is an atheist and Patron of Humanists UK . [ 1 ]
Saiful is a Fellow of the Royal Society of Chemistry (FRSC) since 2008 [ 4 ] and the Institute of Materials, Minerals and Mining (FIMMM), as well as Honorary Fellow of the British Science Association . [ 25 ]
Saiful has received several RSC research awards including 2008 Francis Bacon Medal for Fuel Cell Science, [ 26 ] 2011 Materials Chemistry Division Lecturer Award, 2013 Sustainable Energy Award, [ 27 ] 2013 Wolfson Research Merit Award from the Royal Society , [ 4 ] [ 28 ] [ 29 ] [ 3 ] 2017 Peter Day Award for Materials Chemistry, 2020 Storch Award in Energy Chemistry from the American Chemical Society , [ 30 ] 2022 Hughes Medal from the Royal society, [ 31 ] [ 32 ] and the Robert Perrin Award from Institute of Materials, Minerals and Mining . [ 9 ]
In 2019, he declined a New Year Honours Award of an Order of the British Empire , because he is "never been comfortable with the words ‘British Empire’ in this award and the links to empire, colonialism, and slavery". [ 2 ] | https://en.wikipedia.org/wiki/Saiful_Islam_(chemist) |
SailTimer is a technology for sailboat navigation, which calculates optimal tacking angles, distances and times.
Seafarers have had a dilemma for as long as sailboats could use lift to sail upwind. [ 1 ] [ 2 ] Should you head off the wind more, to get more speed (but at a longer distance)? Or should you sail upwind more, to lessen the distance (but at slower speed)?
Different sailboats have varying capabilities for sailing upwind [ 3 ] because of the condition of their sails, the type of rigging, and the ability to track in the water based on their keel or centerboard design. That means there is not a single rule for everyone; each vessel has its own individual polar plot of boat speed for all of the possible wind angles. [ 4 ] [ 5 ] The mathematical calculations for determining the tacking angles and times with polar plots would not be practical to do mentally.
Civilian access to GPS navigation became available circa 1989. Estimated time of arrival (ETA) is a standard GPS chartplotter parameter, based on the assumption that the route will be a straight line to the destination. However, sailboats typically tack back and forth, creating a longer distance than a straight line. [ 6 ]
SailTimer evaluates tacking distances and boat speeds on different points of sail to determine optimal tacking headings. During the original development of the SailTimer software in 2005–2006, [ 7 ] the term TTD (tm) was coined for "Tacking Time to Destination".
Sailboats can be pushed downwind by the wind, or can use lift to move across or into the wind. [ 8 ] However, for most sailboats the boat speed drops if sailing closer than 45 degrees to the wind. [ 9 ] The highest speed for most sailboats is reaching with the wind from the side or the aft quarter (a beam reach or a broad reach). [ 10 ]
If the destination is upwind but the sailboat goes fastest heading away from this direction, this poses a significant problem: how to choose tack headings with the best tradeoff between maximimizing speed and minimizing distance. The ability to define an efficient tacking route is an important issue in sailboat racing, and for recreational sailing. It is also an important issue of navigational safety, so that the sailboat is able to arrive before dark. Being able to accurately calculate the Tacking Time to Destination also allows a skipper to select a course that avoids bad weather or shipping traffic.
Given the widespread growth of smartphones , a version of SailTimer [ 11 ] is available from the App Store (iOS) for iPhone, iPod and iPad tablets. [ 12 ]
SailTimer also runs on a dedicated handheld device called The Sailing GPS. [ 13 ] An artificial intelligence algorithm allows it to learn the polar plots for an individual sailboat, which it then uses for making decisions on the optimal tacking route and Tacking Time to Destination. | https://en.wikipedia.org/wiki/SailTimer |
The sail area-displacement ratio ( SA/D ) is a calculation used to express how much sail a boat carries relative to its weight . [ 1 ]
In the first equation, the denominator in pounds is divided by 64 to convert it to cubic feet (because 1 cubic foot of salt water weights 64 pounds). The denominator is taken to the 2/3 power to make the entire metric unit-less (without this, the denominator is in cubic feet, and the numerator is in square feet).
It is an indicator of the performance of a boat. [ 2 ] The higher the SA/D, the more lively the boat's sailing performance: [ 3 ]
The SA/D, however, does not provide information about a boat behavior in a storm or upwind. A polar diagram from a velocity prediction program gives a more precise view. [ 4 ]
This article related to shipbuilding is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Sail_area-displacement_ratio |
Sailfish OS is a paid Linux-based operating system based on free software , and open source projects such as Mer as well as including a closed source UI . The project is being developed by the Finnish company Jolla .
The OS first shipped with the original Jolla Phone in 2013; while its sale stopped in 2016, it was supplied with software updates until the end of 2020. It also shipped with Jolla Tablet in 2015 [ 6 ] and from other vendors licensing the OS. [ 7 ] The OS is ported by community enthusiasts to third-party mobile devices including smartphones [ 8 ] and tablet computers . [ 9 ] Sailfish OS can be used for many kinds of devices.
The OS is an evolved continuation of the Linux MeeGo OS previously developed by alliance of Nokia and Intel which itself relies on combined Maemo and Moblin . The MeeGo legacy is contained in the Mer core in about 80% of its code; the Mer name thus expands to ME ego R econstructed. This base is extended by Jolla with a custom user interface and default applications. Jolla and MERproject.org follow a meritocratic system to avoid the mistakes that led to the MeeGo project's then-unanticipated discontinuation. [ 10 ]
The main elements for Sailfish OS 2.0 include:
The Sailfish OS and the Sailfish software development kit (SDK) are based on the Linux kernel and Mer . [ 11 ] [ 12 ] [ 13 ] Sailfish OS includes a multi-tasking graphical shell called "Lipstick" built with Qt by Jolla on top of the Wayland display server protocol . [ 14 ] Jolla uses free and open-source graphics device drivers but the Hybris library allows use of proprietary drivers for Android . [ 15 ] [ 16 ] Jolla fuzzily stated in 2015 that their goal for Sailfish is to become open source eventually, [ 2 ] [ needs update? ] but some key components of Sailfish OS have been licensed proprietary by Jolla from the start and ever since (as of Sailfish OS 4.5.0.24 in September 2023). [ 17 ]
Sailfish OS can run some Android applications through a proprietary compatibility layer. [ 18 ]
Sailfish is targeted at mobile devices. [ citation needed ] Since it inherited around 80% of MeeGo code, Sailfish can be used as a complete general-purpose Linux OS on devices including in vehicle infotainment (IVI), navigation, smart TV, desktops and notebooks, yachts, automotive, e-commerce, home appliances, measuring and control equipment, smart building equipment, etc. See use cases of original MeeGo to compare, [ citation needed ] and the Devices section for devices that run the Sailfish OS .
The Sailfish OS SDK was announced at the Slush Helsinki conference in 2012, and the alpha was published in February 2013. [ 19 ] The SDK, installation and coding tutorials are available for free download from the Sailfish OS website despite the overall license not being open source. [ 1 ]
Sailfish SDK uses Qt with VirtualBox for development, compiling and emulation purposes, in contrast to the simulation method. [ citation needed ] This technique allows compilation on the Sailfish OS and full testing of developed software in the virtual machine , emulating – not simulating – the whole Sailfish OS . [ citation needed ] This also separates development activities and side effects from everything else running on the host computer, leaving it undisturbed by developments and tests. [ 20 ] According to Jolla, development with Sailfish SDK is development on Sailfish OS itself; there are no differences between developed software appearance and behaviour in the SDK and on a device running Sailfish OS . [ citation needed ]
The availability of source code to the SDK allows shaping and rebuilding to companies' or developers' specific needs, [ citation needed ] creating a context-specific environment that is set once and needs no preparation when the device is booted. The SDK runs on the operating systems Android , 32- and 64-bit versions of Linux , 64-bit versions of OS X , and Microsoft Windows . [ 21 ] It can be used for compiling software for Sailfish OS devices from Linux sources. Its general console/terminal mode follows a commonly used standard. Compatible binaries or libraries can also be used. [ citation needed ]
Sailfish OS uses open source Qt APIs (Qt 5, QtQuick 2 etc.) and a proprietary Sailfish Silica for the UI. Standard Linux APIs are provided by the Mer Core. [ 22 ]
Sailfish, Ubuntu and Plasma Active have been cooperating to share common APIs. When successful, this will make the platforms compatible on the API level. [ 23 ]
Sailfish Browser is the default web browser based on Gecko and using embedlite (also known as IPCLiteAPI), a lite-weight embedding API from Mozilla. Uses proprietary components. [ 24 ]
Officially Jolla declares supporting the following 14 languages for the user interface: Danish , German , English (UK) , Spanish , French , Italian , Norwegian , Polish , Portuguese , Finnish , Swedish , Russian , Chinese (mainland) , and Chinese (Hong Kong) . For each of them, the OS has a dedicated keyboard. There are a few more languages which are unofficially supported by community freelancers not under control by Jolla, hence more than 20 languages are supported in total. Additional languages can be installed by skilled users due to the Linux architecture. [ 25 ]
After positive experiences with pushing early updates to a small group of opt-in users for Sailfish Update 9 and for the connectivity hotfix, Jolla has allowed all interested parties to try a new version of Sailfish OS about 1–2 weeks before official release, in a program called "Early access". It is expected to be useful for developers and technically minded users, and a step towards more community integration into the Sailfish release process, including improvement of quality by identifying critical issues which only show up in certain environments or device setups, before rolling the update out to the wider user audience. As an added bonus, it provides a window for developers to test their applications on new releases of Sailfish OS .
In the long term it will help Jolla to establish a developer program with early release candidate access for registered developers, and to have more community involvement in platform development. The first detail Jolla is hoping to learn from this is how it can gather feedback from a large audience in a reasonable way.
Basic details about the early access update:
Sailfish OS has three naming conventions: version number, update number and version name.
When updating an installed Sailfish OS from an earlier release, for example after device factory reset, there are several stop releases [ 38 ] which must not be skipped and have to be installed before continuing on the path to subsequent releases. These releases provide new functionality that is not compatible with previous releases and have to be traversed in order not to put the Sailfish OS installation into an unstable state.
The Sailfish website publishes [ 42 ] an online compendium of knowledge, links and instructions on porting issues.
In addition to its native applications, Sailfish can run some Android applications by installing them from an application store or directly through an APK file . Supported Android versions are 4.1.2 "Jelly Bean" on the original Jolla phone ; 4.4.4 "Kit-Kat" on the Jolla C, Jolla tablet and Xperia X ; 8.1.0 "Oreo", 9 "Pie" and 10 (depending on the Sailfish OS release) on Xperia XA2 , Xperia 10 and Xperia 10 II . [ 43 ] Problems can arise if these applications were built without following Android standards about controls, which might not display correctly and so become unusable.
Sailfish OS uses Alien Dalvik , a proprietary Android compatibility layer. It does not emulate Android, but instead implements its APIs by adapting the Android Open Source Project (AOSP) code to run as an application. Android applications can thus run at native speed without any perceivable slow-down . Sailfish can run both native Sailfish and Android software simultaneously, with the user switching between them on the fly. [ 44 ]
Starting with Alien Dalvik 8.1 (also called "Android App Support" since then), it uses LXC [ 45 ] to improve security by better isolation, in the same way the open source Android compatibility layer Anbox is doing.
Sailfish OS can be used on any hardware with Linux-kernel support and compatible with the middleware utilising the Mer core . Community enthusiasts have ported Sailfish OS to a number of devices this way. [ 46 ] Instead of designation to a specific reference hardware platform, a VirtualBox implementation with the Sailfish SDK is available for development on Linux, OS X and Windows operating systems. This virtual machine implementation contains the whole Sailfish OS isolated from local resources and the local OS to enable convenient evaluation of the behaviour and performance of coded or ported software before deployment on real devices. [ 47 ] [ 48 ]
Manufacturers can provide mobile equipment with a licensed Sailfish OS , or as open source, or combining both and including their own or the operator's modifications and branding for specific markets or purposes.
Due to the relative ease of porting and the open source license, Sailfish OS has also been unofficially ported [ 54 ] to other 3rd-party devices. The Hardware Adaptation Development Kit for porters has been published and is free. [ 55 ] These ports are mostly published on the Maemo and XDA Developers forums, and in the Mer wiki a list of the ports is compiled. [ 56 ] Due to license restrictions, proprietary parts or extensions such as the Alien Dalvik compatibility layer for Android apps are not included. However they can be added, e.g. when a manufacturer or distributor turns it from the community version into an officially supported version for a particular device. From the originally more than 80 ports, there are about 19 ports that are still in active development – as of March 2019 – meaning they have been updated to Sailfish 3:
To display the ease of porting Sailfish OS to other devices, Jolla showed created ports and community ports at events like the Mobile World Congress , Slush and FOSDEM :
Sailfish OS is promoted by Jolla and supported by the open Sailfish Alliance established in 2011, a group established to unite OEM and ODM manufacturers, chipset providers, operators, application developers and retailers. [ 86 ] On 16 August 2012, the user interface was reported to be ready for release. Jolla's CEO Jussi Hurmola stated in a ZDNet interview, " ... Our UI is ready now, we haven't released it yet, we will save it for the product launch and the platform is getting up now so the project looks pretty nice". [ 87 ]
The next day, Jolla's CEO Marc Dillon said on social networking website Twitter that the company had reached the first development target. Sailfish was debuted by the Jolla team, including a worldwide internet stream, as a demo of the OS, and the UI and SDK during the Slush event in Helsinki , Finland, on 21–22 November 2012. The alpha stage of Sailfish OS SDK was published at the end of February 2013 and was made available for free download.
On 16 September 2013, Jolla announced that its OS had been made compatible with Android applications and hardware. [ 88 ] The first telephone to use it was launched on 27 November 2013 at a pop-up DNA Kauppa shop in Helsinki. The first 450 telephones were sold at this event, while the rest of the preordered devices were shipped shortly after. [ 89 ]
In August 2015, version 1.1.9 "Eineheminlampi" was released, which added the main elements of the revamped Sailfish OS 2.0 user interface.
Sailfish OS 2.0.0 was launched with the Jolla Tablet, and existing devices, both smartphones and tablets, from Jolla's official distribution channels are supported with upgrade to Sailfish OS 2.0.0 and following updates.
In May 2016 Jolla announced the Sailfish Community Device Program, supporting developers and members of Sailfish OS community. [ 90 ]
Jolla staff met with members of the Russian technology community to break ground on the new software and promote Sailfish OS , as part of Jolla's BRICS strategy. As a result of those efforts, on 18 May 2015 the Russian minister of communications Nikolai Nikiforov announced plans to replace Apple's iOS and Google's Android platforms with new software based on Sailfish. He intends it to cover 50% of Russian needs in this area during next ten years, in comparison to the 95% currently covered with western technology. [ 91 ] [ 92 ] The Russian version is currently being developed under the brand name Mobile OS "Aurora" (мобильная ОС «Аврора») , [ 93 ] before 2019 as "Sailfish Mobile OS RUS". [ 94 ] [ 95 ] The Chinese multinational technology company Huawei was in talks with the Russian Ministry of Communications to install Aurora OS on tablets for Russia’s population census by August 2020. [ 96 ] Jolla has cut business ties with Russia in 2021. [ 97 ]
Sailfish Alliance is the open alliance established in 2011 by Jolla company to support the MeeGo ecosystem with new products, services and business opportunities around or using Sailfish OS, a Linux operating system combining Mer with proprietary components from Jolla and other parties, for various purposes and mobile devices.
The alliance is seen as a competitor to other groups like Android 's Open Handset Alliance . [ 98 ]
In 2011 some of the MeeGo team working at Nokia left, and were funded by Nokia though their "Bridge" program to fund spin-out projects by ex-employees. [ 99 ] [ 100 ] [ 101 ] The Sailfish Alliance has sought to collaborate between the Finnish software developers, and overseas handset manufacturers, some of which are in China. [ 102 ] [ 103 ] The news media reports that a number of manufacturers in China and India want an alternative to Android . [ 98 ] [ 104 ] [ 105 ]
The Alliance aims to "unite OEM and ODM manufacturers, chipset providers, operators, application developers and retailers." [ 106 ]
The aim of the Alliance is to offer unique differentiation opportunities and sustainable competitive advantage for OEM and ODM manufacturers, chipset providers, operators, application developers, retailers and other interested in sides. [ 107 ]
Sailfish Secure is an open and secure mobile phone platform, based on Sailfish OS. It was introduced publicly in Barcelona, Spain at the Mobile World Congress on 2 March 2015 where plans for Sailfish Secure were presented.
It is based on a security-hardened version of Sailfish OS and SSH's communication encryption and key management platform. It is developed by Jolla (the Sailfish OS designer and developer) together with SSH Communications Security (the inventor of Secure Shell SSH protocol) in collaboration with the Sailfish Alliance .
Sailfish Secure is marketed as having a hardware platform independent approach that allows concept adaptation to local needs, and collaboration with other security partners. End customers like governments or large corporations are able to adapt the product to their preferred or used hardware platform, as it is not tied to a specific hardware or configuration. [ 108 ] [ 109 ] | https://en.wikipedia.org/wiki/Sailfish_OS |
The Saint-Petersburg International Mercantile Exchange ( SPIMEX ) is a Russian commodity exchange [ ru ] incorporated in 2008. It has offices in Moscow , Saint Petersburg and Irkutsk .
SPIMEX offers a wide range of products in exchange-traded refined products , crude oil , natural gas , coal , timber and construction materials as well as commodity derivatives . Its Refined Products Section focuses on spot contracts for all types of domestically traded refined products delivered from a great variety of designated locations executed under the uniform rules. The SPIMEX Derivatives Section focuses on cash-settled futures on the SPIMEX indices for exchange-traded refined products, physically settled futures on refined products and physically settled SPIMEX Urals Crude Futures.
The clearing organization associated with SPIMEX is Nonbank financial institution – central counterparty «RDC» (previously – SDCO).
SPIMEX calculates price indices for domestic exchange-traded and OTC-traded refined products.
In 2022, the volume traded at the SPIMEX Refined Products Section (gasoline, diesel, jet fuel, fuel oil and petrochemicals) was equal to 29.13 million tonnes ; at the SPIMEX Derivatives Section – RUB 13.9 bn and at the SPIMEX Natural Gas Section – 5.7 bcm. [ 1 ]
The total turnover of all trading sections of the Exchange in 2021 increased by 39.5% year-on-year (yoy) to RUB 1.494 trillion, in 2022 it slightly decreased to RUB 1.467 trillion. [ 1 ] The volume traded in the SPIMEX Refined Products Section in 2022 amounted to 29.127 million tonnes (MMT) rising by 7.8% YoY, while the turnover stood at RUB 1.404 trillion ($17.78 bln) enjoying a 3.1% rise YoY. [ 1 ] [ 2 ] [ 3 ]
In March 2022, the Association of European Energy Exchanges (Europex) excluded SPIMEX from its membership due to Russia's invasion of Ukraine . [ 4 ]
Until 2022, the requirements of the Russian government for oil companies to sell part of their products through SPIMEX were in effect. According to these requirements, 11% of gasoline production, 7.5% of diesel fuel, 11% of jet fuel, 3% of residual fuel oil production and 7.5% of LPG were subject to sale through the exchange. [ 5 ]
SPIMEX has been trading:
SPIMEX — the primary trading venue for exchange-traded refined products in Russia.
In 2016, the volume of refined products and petrochemicals traded on SPIMEX amounted to 17.16 million tonnes. The number of trading participants exceeded 1,900 including all Russian majors; the list of SPIMEX designated delivery points include all key domestic refineries; the list of commodities accepted to trading includes all types of domestic refined products.
By 2021, the trade in petroleum products has grown to 27.03 million tons (+ 16.6% compared to 2020), by 2022 to 29.13 million tons (+ 7.8% compared to 2021). [ 3 ] [ 8 ] [ 1 ]
Territorial indices
The average price for refined products at large Russian refineries located in European Russia, the Urals & Western Siberia and Eastern Siberia & the Russian Far East.
Regional indices
The average price for refined products at 9 large domestic demand centers.
Composite index
A unified indicator of Russian domestic refined products which measures price performance of an average tonne of exchange-traded light refined products.
National indices
The average price for refined products at large refineries located all over Russia.
SPIMEX launched trading in crude oil in 2013. In 2022, the volume traded at the SPIMEX Crude Oil Section stood at 519,400 tonnes (+ 164,4% y-o-y) with the turnover amounting to RUB 16.974 bn. [ 1 ]
SPIMEX offers a variety of futures contracts (at present there are more than 20 instruments available). The volume traded at the SPIMEX Derivatives Section in 2022 reached 69,326 futures contracts in the total amount of RUB 13.9 bn. [ 1 ]
More than 10 products are currently offered by the SPIMEX Derivatives Section, including, in particular:
Underlying commodities: crude oil; diesel; Gasoline Regular 92; Gasoline Premium 95 and the SPIMEX indices for exchange-traded petroleum products. Physical delivery is a distinctive feature of SPIMEX commodity-based futures.
Risk Management System (RMS)
Performance of the obligations under futures contracts is guaranteed by the Clearing House.
On 24 October 2014, SPIMEX launched trading in natural gas . [ 9 ]
SPIMEX designated balancing points (located around compressor stations) are as follows: Nadym, Lokosovo and Parabel. Trading Participants include largest domestic natural gas producers and end-users (utilities, fertilizer and metallurgy companies). [ 9 ]
In October 2015 SPIMEX launched a day-ahead contracts trades and in October 2016 - trades for delivery on national holidays and weekends. [ 9 ]
In 2016, the volume traded at the SPIMEX Natural Gas Section amounted to 16.812 bcm (+119.8% y-o-y), in 2021 – 6.691 bcm (-58.3% y-o-y) [ 3 ] and in 2022 – 5.700 bcm (-14.8% y-o-y). [ 1 ]
Active development of the market continues. The first stage of commercial balancing of natural gas traded on the Exchange has been implemented. Buyers are now able to sell on the Exchange volumes of natural gas that were purchased earlier, but were not drawn by the end of the day. [ 1 ]
On 11 July 2014, SPIMEX launched trading in timber . Deliveries of conifer timber traded on SPIMEX originate in the Irkutsk Region of Russia. The Exchange brings together over 60 entities, including major logging companies, forest leaseholders and timber processing businesses. SPIMEX plans to add new trading instruments, to expand geographic reach and in the long run to launch a cross-border delivery mechanism.
In 2022, the volume traded at the SPIMEX Timber & Construction Materials Section amounted to 4,012 million cubic meters. The number of trades made stood at 2,617. [ 1 ]
SPIMEX is authorized to register OTC transactions in the following exchange-traded commodities:
Data on such OTC transactions is used for calculation of the relevant SPIMEX indices. In 2022, volumes set in the relevant OTC contacts and the number of registered OTC transactions were broken down by product as follows:
In 2022, the number of companies which registered their OTC transactions with SPIMEX grew up to 1141. | https://en.wikipedia.org/wiki/Saint-Petersburg_International_Mercantile_Exchange |
In the mathematical theory of elasticity , Saint-Venant's compatibility condition defines the relationship between the strain ε {\displaystyle \varepsilon } and a displacement field u {\displaystyle \ u} by
where 1 ≤ i , j ≤ 3 {\displaystyle 1\leq i,j\leq 3} . Barré de Saint-Venant derived the compatibility condition for an arbitrary symmetric second rank tensor field to be of this form, this has now been generalized to higher rank symmetric tensor fields on spaces of dimension n ≥ 2 {\displaystyle n\geq 2}
For a symmetric rank 2 tensor field F {\displaystyle F} in n-dimensional Euclidean space ( n ≥ 2 {\displaystyle n\geq 2} ) the integrability condition takes the form of the vanishing of the Saint-Venant's tensor W ( F ) {\displaystyle W(F)} [ 1 ] defined by
The result that, on a simply connected domain W=0 implies that strain is the symmetric derivative of some vector field, was first described by Barré de Saint-Venant in 1860 [ 2 ] and proved rigorously by Beltrami in 1886. [ 3 ] For non-simply connected domains there are finite dimensional spaces of symmetric tensors with vanishing Saint-Venant's tensor that are not the symmetric derivative of a vector field. The situation is analogous to de Rham cohomology [ 4 ]
The Saint-Venant tensor W {\displaystyle W} is closely related to the Riemann curvature tensor R i j k l {\displaystyle R_{ijkl}} . Indeed the first variation R {\displaystyle R} about the Euclidean metric with a perturbation in the metric F {\displaystyle F} is precisely W {\displaystyle W} . [ 5 ] Consequently the number of independent components of W {\displaystyle W} is the same as R {\displaystyle R} [ 6 ] specifically n 2 ( n 2 − 1 ) 12 {\displaystyle {\frac {n^{2}(n^{2}-1)}{12}}} for dimension n. [ 7 ] Specifically for n = 2 {\displaystyle n=2} , W {\displaystyle W} has only one independent component where as for n = 3 {\displaystyle n=3} there are six.
In its simplest form of course the components of F {\displaystyle F} must be assumed twice continuously differentiable, but more recent work [ 3 ] proves the result in a much more general case.
The relation between Saint-Venant's compatibility condition and Poincaré's lemma can be understood more clearly using a reduced form of W {\displaystyle W} the Kröner tensor [ 6 ]
where ϵ {\displaystyle \epsilon } is the permutation symbol . For n = 3 {\displaystyle n=3} , K {\displaystyle K} is a symmetric rank 2 tensor field. The vanishing of K {\displaystyle K} is equivalent to the vanishing of W {\displaystyle W} and this also shows that there are six independent components for the important case of three dimensions. While this still involves two derivatives rather than the one in the Poincaré lemma, it is possible to reduce to a problem involving first derivatives by introducing more variables and it has been shown that the resulting 'elasticity complex' is equivalent to the de Rham complex . [ 8 ]
In differential geometry the symmetrized derivative of a vector field appears also as the Lie derivative of the metric tensor g with respect to the vector field.
where indices following a semicolon indicate covariant differentiation. The vanishing of W ( T ) {\displaystyle W(T)} is thus the integrability condition for local existence of U {\displaystyle U} in the Euclidean case. As noted above this coincides with the vanishing of the linearization of the Riemann curvature tensor about the Euclidean metric.
Saint-Venant's compatibility condition can be thought of as an analogue, for symmetric tensor fields, of Poincaré's lemma for skew-symmetric tensor fields ( differential forms ). The result can be generalized to higher rank symmetric tensor fields. [ 9 ] [ 10 ] .Let F be a symmetric rank-k tensor field on an open set in n-dimensional Euclidean space , then the symmetric derivative is the rank k+1 tensor field defined by
where we use the classical notation that indices following a comma indicate differentiation and groups of indices enclosed in brackets indicate symmetrization over those indices. The Saint-Venant tensor W {\displaystyle W} of a symmetric rank-k tensor field T {\displaystyle T} is defined by
with
On a simply connected domain in Euclidean space W = 0 {\displaystyle W=0} implies that T = d F {\displaystyle T=dF} for some rank k-1 symmetric tensor field F {\displaystyle F} .
Denisjuk [ 11 ] gives an invariant form of the generalized Saint-Venant tensor as a section of the bundle S k ( Λ 2 T ∗ R n ) {\displaystyle S^{k}(\Lambda ^{2}T^{*}\mathbb {R} ^{n})} . That is the k-th symmetric power of the second skew symmetric power of the cotangent bundle. He defines W {\displaystyle W} as the alternation of the m-th partial derivatives of T {\displaystyle T} , and observes that for $m=1$ it reduces simply to the exterior derivative. This work, and Sharafutdinov's, stem from the study of the longitudinal ray transform , of symmetric tensor fields. Here the null space is exactly symmetric derivatives of tensor fields one rank lower, and the Saint-Venant tensor can be recovered by an explicit reconstruction formula. | https://en.wikipedia.org/wiki/Saint-Venant's_compatibility_condition |
In solid mechanics , it is common to analyze the properties of beams with constant cross section. Saint-Venant's theorem states that the simply connected cross section with maximal torsional rigidity is a circle. [ 1 ] It is named after the French mathematician Adhémar Jean Claude Barré de Saint-Venant .
Given a simply connected domain D in the plane with area A , ρ {\displaystyle \rho } the radius and σ {\displaystyle \sigma } the area of its greatest inscribed circle, the torsional rigidity P of D is defined by
Here the supremum is taken over all the continuously differentiable functions vanishing on the boundary of D . The existence of this supremum is a consequence of Poincaré inequality .
Saint-Venant [ 2 ] conjectured in 1856 that
of all domains D of equal area A the circular one has the greatest torsional rigidity, that is
A rigorous proof of this inequality was not given until 1948 by Pólya . [ 3 ] Another proof was given by Davenport and reported in. [ 4 ] A more general proof and an estimate
is given by Makai. [ 1 ] | https://en.wikipedia.org/wiki/Saint-Venant's_theorem |
The Sakaguchi test is a chemical test used to detect presence of arginine in proteins. It is named after the Japanese food scientist and organic chemist, Shoyo Sakaguchi (1900–1995) who described the test in 1925. [ 1 ] The Sakaguchi reagent used in the test consists of 1-Naphthol and a drop of sodium hypobromite . The guanidino (–C group in arginine reacts with the Sakaguchi reagent to form a red-coloured complex. [ 2 ] [ 3 ] [ 4 ] [ 5 ]
This article about analytical chemistry is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Sakaguchi_test |
In physics , the Sakuma–Hattori equation is a mathematical model for predicting the amount of thermal radiation , radiometric flux or radiometric power emitted from a perfect blackbody or received by a thermal radiation detector.
The Sakuma–Hattori equation was first proposed by Fumihiro Sakuma, Akira Ono and Susumu Hattori in 1982. [ 1 ] In 1996, a study investigated the usefulness of various forms of the Sakuma–Hattori equation. This study showed the Planckian form to provide the best fit for most applications. [ 2 ] This study was done for 10 different forms of the Sakuma–Hattori equation containing not more than three fitting variables. In 2008, BIPM CCT-WG5 recommended its use for radiation thermometry measurement uncertainty budgets below 960 °C. [ 3 ]
The Sakuma–Hattori equation gives the electromagnetic signal from thermal radiation based on an object's temperature . The signal can be electromagnetic flux or signal produced by a detector measuring this radiation. It has been suggested that below the silver point, [ a ] a method using the Sakuma–Hattori equation be used. [ 1 ] In its general form it looks like [ 3 ] S ( T ) = C exp ( c 2 λ x T ) − 1 , {\displaystyle S(T)={\frac {C}{\exp \left({\frac {c_{2}}{\lambda _{x}T}}\right)-1}},} where: [ clarification needed ]
The Planckian form is realized by the following substitution: λ x = A + B T {\displaystyle \lambda _{x}=A+{\frac {B}{T}}}
Making this substitution renders the following the Sakuma–Hattori equation in the Planckian form.
The Planckian form is recommended for use in calculating uncertainty budgets for radiation thermometry [ 3 ] and infrared thermometry . [ 7 ] It is also recommended for use in calibration of radiation thermometers below the silver point. [ 3 ]
The Planckian form resembles Planck's law .
S ( T ) = c 1 λ 5 [ exp ( c 2 λ T ) − 1 ] {\displaystyle S(T)={\frac {c_{1}}{\lambda ^{5}\left[\exp \left({\frac {c_{2}}{\lambda T}}\right)-1\right]}}}
However the Sakuma–Hattori equation becomes very useful when considering low-temperature, wide-band radiation thermometry. To use Planck's law over a wide spectral band, an integral like the following would have to be considered:
S ( T ) = ∫ λ 1 λ 2 c 1 λ 5 [ exp ( c 2 λ T ) − 1 ] d λ {\displaystyle S(T)=\int _{\lambda _{1}}^{\lambda _{2}}{\frac {c_{1}}{\lambda ^{5}\left[\exp \left({\frac {c_{2}}{\lambda T}}\right)-1\right]}}d\lambda }
This integral yields an incomplete polylogarithm function, which can make its use very cumbersome.
The standard numerical treatment expands the incomplete integral in a geometric series of the exponential ∫ 0 λ 2 c 1 λ 5 [ exp ( c 2 λ T ) − 1 ] d λ = c 1 ( T c 2 ) 4 ∫ c 2 / ( λ 2 T ) ∞ x 3 e x − 1 d x {\displaystyle \int _{0}^{\lambda _{2}}{\frac {c_{1}}{\lambda ^{5}\left[\exp \left({\frac {c_{2}}{\lambda T}}\right)-1\right]}}d\lambda =c_{1}\left({\frac {T}{c_{2}}}\right)^{4}\int _{c_{2}/(\lambda _{2}T)}^{\infty }{\frac {x^{3}}{e^{x}-1}}dx} after substituting λ = c 2 x T , d λ = − c 2 x 2 T d x . {\displaystyle \lambda ={\tfrac {c_{2}}{xT}},\ d\lambda ={\tfrac {-c_{2}}{x^{2}Tdx}}.} Then J ( c ) ≡ ∫ c ∞ x 3 e x − 1 d x = ∫ c ∞ x 3 e − x 1 − e − x d x = ∫ c ∞ ∑ n ≥ 1 x 3 e − n x d x = ∑ n ≥ 1 e − n c ( n c ) 3 + 3 ( n c ) 2 + 6 n c + 6 n 4 {\displaystyle {\begin{aligned}J(c)&\equiv \int _{c}^{\infty }{\frac {x^{3}}{e^{x}-1}}dx=\int _{c}^{\infty }{\frac {x^{3}e^{-x}}{1-e^{-x}}}dx\\[4pt]&=\int _{c}^{\infty }\sum _{n\geq 1}x^{3}e^{-nx}dx\\[4pt]&=\sum _{n\geq 1}e^{-nc}{\frac {(nc)^{3}+3(nc)^{2}+6nc+6}{n^{4}}}\end{aligned}}} provides an approximation if the sum is truncated at some order.
The Sakuma–Hattori equation shown above was found to provide the best curve-fit for interpolation of scales for radiation thermometers among a number of alternatives investigated. [ 2 ]
The inverse Sakuma–Hattori function can be used without iterative calculation. This is an additional advantage over integration of Planck's law.
The 1996 paper investigated 10 different forms. They are listed in the chart below in order of quality of curve-fit to actual radiometric data. [ 2 ] | https://en.wikipedia.org/wiki/Sakuma–Hattori_equation |
Sakura Editor is a free and open-source Japanese text editor for Microsoft Windows .
Sakura Editor was started by Take ( たけ ), the original author, around 1998 and the source code was made public around 2000. Development was carried out on SourceForge until May 2018, then it was moved to GitHub in June of the same year. [ 2 ]
Sakura Editor uses cream color as the default background. It supports keyword highlighting, outline analysis, and completion. In addition, it has basic functions such as multiple encodings , grep , and macros . [ 3 ] [ 4 ] It notably supports handling documents with mixed line breaks. It also supports various character encodings such as Shift_JIS , ISO-2022-JP , EUC-JP , UTF-16 , UTF-8 , and UTF-7 .
There are currently official 32-bit and alpha 64-bit versions.
Since v2.4.0, it has been distributed under the zlib license . [ 2 ]
This software article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Sakura_(text_editor) |
The Sakurai reaction (also known as the Hosomi–Sakurai reaction ) is the chemical reaction of carbon electrophiles (such as a ketone shown here) with allyltrimethylsilane catalyzed by strong Lewis acids . [ 1 ] [ 2 ] [ 3 ] The reaction achieves results similar to the addition of an allyl Grignard reagent to the carbonyl.
Strong Lewis acids such as titanium tetrachloride , boron trifluoride , tin tetrachloride , and AlCl(Et) 2 are all effective in promoting the Sakurai reaction. The reaction involves electrophilic allyl shift via a beta-silyl carbocationic intermediate, the beta-silicon effect . [ 4 ]
Allylation of a carbonyl ketone (compound containing a ketone group and two different functional groups) has been shown. In the given reaction, the electrophilic compound (carbon with a ketone group) is treated with titanium tetrachloride, a strong Lewis acid and allyltrimethylsilane. According to the general principle, the Lewis acid first activates the electrophilic carbon in presence of allyltrimethylsilane which then undergoes nucleophilic attack from electrons on the allylic silane. [ 5 ] The silicon plays the key role in stabilizing the carbocation of carbon at the β-position. The Sakurai reaction is also applicable for other functional groups such as enones , where conjugate addition is usually seen. In figure 2, the Sakurai reaction has been shown using a cinnamoyl ketone. This reaction follows the same mechanism as the previous reaction shown here.
As displayed in the scheme, the Sakurai reaction is proposed to give a secondary carbocation intermediate. Secondary carbocations are high in energy, however it is stabilized by the silicon substituent ("β-silicon effect", a form of silicon-hyperconjugation). | https://en.wikipedia.org/wiki/Sakurai_reaction |
Sala Nanyanzi Senkayi is an African environmental scientist at the United States Environmental Protection Agency . She was the first Ugandan -born woman to win the Presidential Early Career Award for Scientists and Engineers .
Senkayi is the daughter of Abu Senkayi and Sunajeh Senkayi. Her family are from Butambala District in Uganda. Her father was an environmental scientist and worked at Texas A&M University as a research scientist from 1977. [ 1 ] [ 2 ]
Senkayi obtained a bachelor's degree in biomedical sciences from Texas A&M University in College Station, Texas . She joined the University of Texas at Arlington , earning two more Bachelor's degrees in microbiology and biology . Later, she earned a master's degree (2010) and a PhD (2012) degrees in environmental and earth sciences from the same university. [ 3 ] Her PhD thesis considered the association between childhood leukaemia and proximity to airports in Texas. [ 4 ] She found that benzene emissions were a predictor for childhood leukaemia. [ 4 ] During her graduate studies Muwenda Mutebi II of Buganda and Sylvia Nnaginda visited her in Texas. [ 5 ]
Senkayi joined the United States Environmental Protection Agency in 2007. [ 6 ] She works with local children in schools and colleges talking about the environment. [ 5 ] She initiated the EPA Converses with Students webcast, an opportunity for children to speak to scientists who worked on environmental protection on Earth Day . [ 7 ] [ 8 ] Her research focuses on water quality protection and she is the Water Quality Division Quality Assurance Officer. [ 3 ] In 2017 Senkayi was awarded the Presidential Early Career Award for Scientists and Engineers for her "transformative" community outreach and research. [ 3 ] [ 9 ] | https://en.wikipedia.org/wiki/Sala_Senkayi |
A salad spinner , also known as a salad tosser , is a kitchen tool used to wash and remove excess water from salad greens . It uses centrifugal force to separate the water from the leaves, enabling salad dressing to stick to the leaves without dilution.
Salad spinners are usually made from plastic and include an outer bowl with an inner removable colander or strainer basket. A cover, which fits around the outside bowl, contains a spinning mechanism that when initiated causes the inside strainer to rotate rapidly. The water is driven through the slits in the basket into the outer bowl. There are a number of different mechanisms used to operate the device, including crank handles, push buttons and pull-cords. The salad spinner is generally easy to use, though its large and rigid shape has been criticized by food editor Leanne Kitchen and Herald-Journal reporter Mary Hunt. A salad spinner is often considered bulky and difficult to store.
Although devices used to wash, dry and spin salad have long been in existence, including one from the 19th century, the modern mechanism-operated spinner originated in the early 1970s. In 1974, the Mouli Manufacturing Co. introduced a crank-operated salad spinner to the American market; other companies were not far behind with their own patented variations. The product sold favorably and demand was high, with stores struggling to keep it in stock. Despite the product's popularity, however, it was not entirely without criticism; some were skeptical about the necessity of "another gourmet gadget". [ 1 ]
Although the invention of the salad spinner is considered to be modern, earlier devices, including one from the 19th century, did exist and performed similar functions. [ 2 ] When the salad spinner was introduced to the mass market in the 1970s, a number of other techniques and products were already available and employed for the drying of vegetables and salad. One such device was a wire basket dryer, in essence a collapsible colander, which could be shaken or spun to expel the excess water. This method has been criticized by some for its impracticalities and according to one writer, the process was "akin to standing near a dog that’s shaking himself dry." [ 3 ] [ 4 ] Another product was a wire lettuce dryer designed for use in the sink. A basket was fixed with suction cups to the bottom of the sink, and pushing a pump caused the basket to spin around a center post, often spraying expelled water on the operator. [ 3 ] Paper or fabric towels were also commonly used for drying salad and vegetables after washing, however the method was perceived as time-consuming and costly. [ 3 ]
In 1971, Jean Mantelet filed a patent for a "Salad Dryer," a hand-operated, centrifugally-driven device along with another called the "Household Drying Machine" which could also be used for salads. [ 5 ] [ 6 ] [ 7 ] Mantelet was a prominent designer of domestic appliances and the founder of the French company Moulinex . [ 8 ] He patented another salad dryer device in 1974. [ 9 ] Mantelet was particularly proud of his salad dryer design. [ 5 ] Of the new product, one user commented that, "it saves shaking my salad basket out of the kitchen window." [ 5 ]
Gilberte Fouineteau, another French inventor, has been credited as the creator of the modern salad spinner. He filed a patent for a device in 1973. It too used centrifugal force to dry and drain vegetables and salads. The patent describes its difference being the removable basket and a lack of a central post. [ 10 ] [ 11 ]
The Mouli Manufacturing Co., a kitchen supply brand, introduced the salad dryer to the American market in 1974. [ 1 ] [ 3 ] Others companies soon followed with their own, similar versions of the device. [ 3 ] The salad spinner proved to be an immediate success however it was not without some skepticism. [ 1 ] [ 3 ] The product received criticism for being “another gourmet gadget” and the latest piece of “kitchen junk” to add to the growing list of new appliances which included hot dog cookers , cookie shooters and electric potato peelers . [ 1 ]
“Salad spinner. Salad dryers. Lettuce spinners. Salad washers. Whatever they’re calling them, our group of paper towel diehards approached those plastic tubs with hesitance. Actually, for some, there was downright hostility.”
Despite reservations, the salad dryer was selling well in the American market. Over the five-year period since the product's introduction, sales of the dryer had quadrupled, with an estimated 500,000 units said to have been sold in 1978 alone. Cookware stores were unable to keep hold with demand and reported being out of stock of the device. [ 1 ] The product even appealed to skeptics and was thought to be a time saver compared to the “tedious hand method of patting dry each leaf” that was known for leaving "soggy linen" and towels. [ 1 ] A report at the time estimated that the money spent on a month's supply of paper towel reserved for drying lettuce could easily be enough to pay for a new salad dryer. [ 3 ]
Salad spinners are usually made from plastic. [ 12 ] The design is an outer bowl with an inner, removable colander or strainer basket. A cover, which fits around the outside bowl, contains a spinning mechanism which causes the inside strainer to rotate rapidly. [ 10 ] There are a number of different mechanisms used to operate the device, including the use of a crank handle, push button or pull-cord. [ 12 ]
Raw leaves in a salad need to be clean as well as dry. Salad which has not been properly washed can be potentially harmful, although generally the risk of illness is low. Listeria , E. coli , and other causes of food poisoning [ 17 ] [ 18 ] have been known to be present in unwashed salads. Costas Katsigris suggests that an increased rise in foodborne illness outbreaks has encouraged the use of salad washers and spinners. [ 16 ]
Drying the leaves for the salad is important as salad dressings and oils do not stick well to wet lettuce or salad leaves. Salad greens left in water for a long period of time will go limp, and fragile salad leaves can be easily damaged and bruised if handled harshly during the washing and drying process. [ 3 ] [ 16 ]
The greens are placed in the colander section of the spinner and the container is filled with water. The floating salad is spun and left to sit before the water is poured out. This process can be repeated until no visible traces of dirt or sand remain. Once drained, the greens are spun, which generates a centripetal force that drives the excess moisture, through the perforation in the central strainer, to the outer bowl. [ 10 ] [ 19 ]
Salad spinners are considered to be an easy product to use and operate, [ 12 ] but have been criticized for being bulky, space-consuming and difficult-to-store. [ 2 ] [ 12 ] | https://en.wikipedia.org/wiki/Salad_spinner |
A salamander (or deadman's foot, furnace sow or furnace bear) in metallurgy means all liquid and solidified
materials in the hearth of a blast furnace below the tap hole.
Salamander tapping is removing the remaining hot metal and slag, while still in a molten state, from the blast furnace to allow, for example, a safe and efficient intermediate repair. The salamander is tapped by drilling an upward-slanting outlet in the blast furnace hearth. Initially a metal drill is used, but to complete the process an oxygen lance is deployed.
If the salamander is allowed to cool it cannot easily be removed from the furnace, and may require drilling and blasting with explosives. [ 1 ]
This industry -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Salamander_(metallurgy) |
Salbutamol , also known as albuterol and sold under the brand name Ventolin among others, [ 1 ] is a medication that opens up the medium and large airways in the lungs . [ 7 ] It is a short-acting β 2 adrenergic receptor agonist that causes relaxation of airway smooth muscle . [ 7 ] It is used to treat asthma , including asthma attacks and exercise-induced bronchoconstriction , as well as chronic obstructive pulmonary disease (COPD). [ 7 ] It may also be used to treat high blood potassium levels . [ 8 ] Salbutamol is usually used with an inhaler or nebulizer , but it is also available in a pill, liquid, and intravenous solution. [ 7 ] [ 9 ] Onset of action of the inhaled version is typically within 15 minutes and lasts for two to six hours. [ 7 ]
Common side effects include shakiness , headache , fast heart rate , dizziness , and feeling anxious . [ 7 ] Serious side effects may include worsening bronchospasm , irregular heartbeat , and low blood potassium levels . [ 7 ] It can be used during pregnancy and breastfeeding , but safety is not entirely clear. [ 7 ] [ 10 ]
Salbutamol was patented in 1966 in Britain and became commercially available in the UK in 1969. [ 11 ] [ 12 ] It was approved for medical use in the United States in 1982. [ 7 ] It is on the World Health Organization's List of Essential Medicines . [ 13 ] Salbutamol is available as a generic medication . [ 7 ] In 2022, it was the seventh most commonly prescribed medication in the United States, with more than 59 million prescriptions. [ 14 ] [ 15 ]
Salbutamol is typically used to treat bronchospasm (due to any cause—allergic asthma or exercise-induced), as well as chronic obstructive pulmonary disease . [ 7 ] It is also one of the most common medicines used in rescue inhalers (short-term bronchodilators to alleviate asthma attacks ). [ 16 ]
As a β 2 agonist, salbutamol also has use in obstetrics . Intravenous salbutamol can be used as a tocolytic to relax the uterine smooth muscle to delay premature labor . While preferred over agents such as atosiban and ritodrine , its role has largely been replaced by the calcium channel blocker nifedipine , which is more effective and better tolerated. [ 17 ]
Salbutamol has been used to treat acute hyperkalemia , as it stimulates potassium flow into cells, thus lowering the potassium in the blood. [ 8 ]
Two recent studies have suggested that salbutamol reduces the symptoms of newborns and adolescents with myasthenia gravis and transient neonatal myasthenia gravis . [ 18 ] [ 19 ]
The most common side effects are fine tremor , anxiety , headache , muscle cramps , dry mouth , and palpitation . [ 20 ] Other symptoms may include tachycardia , arrhythmia , flushing of the skin , myocardial ischemia (rare), and disturbances of sleep and behaviour. [ 20 ] Rarely occurring, but of importance, are allergic reactions of paradoxical bronchospasms, urticaria (hives), angioedema , hypotension , and collapse. High doses or prolonged use may cause hypokalemia , which is of concern especially in patients with kidney failure and those on certain diuretics and xanthine derivatives. [ 20 ]
Salbutamol metered dose inhalers have been described as the "single biggest source of carbon emissions from NHS medicines prescribing" due to the propellants used in the inhalers. Dry powder inhalers are recommended as a low-carbon alternative. [ 21 ]
The tertiary butyl group in salbutamol makes it more selective for β 2 receptors, [ 22 ] which are the predominant receptors on the bronchial smooth muscles . Activation of these receptors causes adenylyl cyclase to convert ATP to cAMP , beginning the signalling cascade that ends with the inhibition of myosin phosphorylation and lowering the intracellular concentration of calcium ions (myosin phosphorylation and calcium ions are necessary for muscle contractions). The increase in cAMP also inhibits inflammatory cells in the airway, such as basophils , eosinophils , and most especially mast cells , from releasing inflammatory mediators and cytokines. [ 23 ] [ 24 ] Salbutamol and other β 2 receptor agonists also increase the conductance of channels sensitive to calcium and potassium ions, leading to hyperpolarization and relaxation of bronchial smooth muscles. [ 25 ]
Salbutamol is either filtered out by the kidneys directly or is first metabolized into the 4′- O -sulfate, which is excreted in the urine. [ 9 ]
Salbutamol is sold as a racemic mixture . The ( R )-(−)- enantiomer ( CIP nomenclature ) is shown in the image at right (top), and is responsible for the pharmacologic activity; the ( S )-(+)-enantiomer (bottom) blocks metabolic pathways associated with elimination of itself and of the pharmacologically active enantiomer ( R ). [ 26 ] The slower metabolism of the ( S )-(+)-enantiomer also causes it to accumulate in the lungs, which can cause airway hyperreactivity and inflammation. [ 27 ] Potential formulation of the R form as an enantiopure drug is complicated by the fact that the stereochemistry is not stable, but rather the compound undergoes racemization within a few days to weeks, depending on pH . [ 28 ]
The direct separation of Salbutamol enantiomers and the control of enantiomeric purity has been described by thin-layer chromatography . [ 29 ]
Salbutamol was discovered in 1966, by a research team led by David Jack at the Allen and Hanburys laboratory (now a subsidiary of Glaxo ) in Ware, Hertfordshire , England, and was launched as Ventolin in 1969. [ 30 ]
The 1972 Munich Olympics were the first Olympics where anti-doping measures were deployed, and at that time β 2 agonists were considered to be stimulants with high risk of abuse for doping. Inhaled salbutamol was banned from those games, but by 1986 was permitted (although oral β 2 agonists were not). After a steep rise in the number of athletes taking β 2 agonists for asthma in the 1990s, Olympic athletes were required to provide proof that they had asthma in order to be allowed to use inhaled β 2 agonists. [ 31 ]
In February 2020, the U.S. Food and Drug Administration (FDA) approved the first generic of an albuterol sulfate inhalation aerosol for the treatment or prevention of bronchospasm in people four years of age and older with reversible obstructive airway disease and the prevention of exercise-induced bronchospasm in people four years of age and older. [ 32 ] [ 33 ] The FDA granted approval of the generic albuterol sulfate inhalation aerosol to Perrigo Pharmaceutical. [ 32 ]
In April 2020, the FDA approved the first generic of Proventil HFA (albuterol sulfate) metered dose inhaler, 90 μg per inhalation, for the treatment or prevention of bronchospasm in patients four years of age and older who have reversible obstructive airway disease, as well as the prevention of exercise-induced bronchospasm in this age group. [ 34 ] The FDA granted approval of this generic albuterol sulfate inhalation aerosol to Cipla Limited. [ 34 ]
In 2020, generic versions were approved in the United States. [ 32 ] [ 34 ]
Salbutamol is the international nonproprietary name (INN) while albuterol is the United States Adopted Name (USAN). [ 35 ] The drug is usually manufactured and distributed as the sulfate salt (salbutamol sulfate).
It was first sold by Allen & Hanburys (UK) under the brand name Ventolin, and has been used for the treatment of asthma ever since. [ 36 ] The drug is marketed under many names worldwide. [ 1 ]
Albuterol and other beta-2 adrenergic agonists are used by some recreational bodybuilders. [ 37 ] [ 38 ]
As of 2011 [update] there was no evidence that an increase in physical performance occurs after inhaling salbutamol, but there are various reports for benefit when delivered orally or intravenously. [ 39 ] [ 40 ] In spite of this, salbutamol required "a declaration of Use in accordance with the International Standard for Therapeutic Use Exemptions" under the 2010 WADA prohibited list. This requirement was relaxed when the 2011 list was published to permit the use of "salbutamol (maximum 1600 micrograms over 24 hours) and salmeterol when taken by inhalation in accordance with the manufacturers' recommended therapeutic regimen." [ 41 ] [ 42 ]
Abuse of the drug may be confirmed by detection of its presence in plasma or urine, typically exceeding 1,000 ng/mL. The window of detection for urine testing is on the order of just 24 hours, given the relatively short elimination half-life of the drug, [ 43 ] [ 44 ] [ 45 ] estimated at between 5 and 6 hours following oral administration of 4 mg. [ 23 ]
Salbutamol has been studied in subtypes of congenital myasthenic syndrome associated with mutations in Dok-7 . [ 46 ]
It has also been tested in a trial aimed at treatment of spinal muscular atrophy ; it is speculated to modulate the alternative splicing of the SMN2 gene, increasing the amount of the SMN protein , the deficiency of which is regarded as a cause of the disease. [ 47 ] [ 48 ]
Albuterol increases energy expenditure by 10-15 percent at a therapeutic dose for asthma and around 25 percent at a higher, oral dose. In several human studies, albuterol increased lean body mass, reduced fat mass, and caused lipolysis ; it has been studied for use as an anti-obesity and anti-muscle wasting medication when taken orally. [ 49 ] [ 50 ]
Salbutamol's low toxicity makes it safe for other animals and thus is the medication of choice for treating acute airway obstruction in most species. [ 27 ] It is usually used to treat bronchospasm or coughs in cats and dogs and used as a bronchodilator in horses with recurrent airway obstruction ; it can also be used in emergencies to treat asthmatic cats. [ 51 ] [ 52 ]
Toxic effects require an extremely high dose, and most overdoses are due to dogs chewing on and puncturing an inhaler or nebulizer vial. [ 53 ] | https://en.wikipedia.org/wiki/Salbutamol |
Salen refers to a tetradentate C 2 -symmetric ligand synthesized from salicylaldehyde ( sal ) and ethylenediamine ( en ). It may also refer to a class of compounds, which are structurally related to the classical salen ligand, primarily bis- Schiff bases . Salen ligands are notable for coordinating a wide range of different metals, which they can often stabilise in various oxidation states. [ 1 ] For this reason salen-type compounds are used as metal deactivators . Metal salen complexes also find use as catalysts . [ 2 ]
H 2 salen may be synthesized by the condensation of ethylenediamine and salicylaldehyde. [ 3 ]
Complexes of salen with metal cations can often be made in situ, i.e., without isolating the H 2 salen. [ 4 ] [ 5 ] | https://en.wikipedia.org/wiki/Salen_ligand |
Salesforce management systems (also sales force automation systems ( SFA )) are information systems used in customer relationship management (CRM) marketing and management that help automate some sales and sales force management functions. They are often combined with a marketing information system , in which case they are often called CRM systems . | https://en.wikipedia.org/wiki/Sales_force_management_system |
Salicylaldoxime is an organic compound described by the formula C 6 H 4 CH=NOH-2-OH. It is the oxime of salicylaldehyde . This crystalline, colorless solid is a chelator and sometimes used in the analysis of samples containing transition metal ions , with which it often forms brightly coloured coordination complexes . [ 1 ]
Salicylaldoxime is the conjugate acid of a bidentate ligand:
In highly acidic media, the ligand protonates, and the metal aquo complex and aldoxime are liberated. In this way the ligand is used as a recyclable extractant.
It typically forms charge-neutral complexes with divalent metal ions.
In the era when metals were analysed by spectrophotometry , many chelating ligands were developed that selectively formed brightly coloured complexes with particular metal ions. This methodology has been eclipsed with the introduction of inductively coupled plasma methodology. Salicylaldoxime can be used to selectively precipitate metal ions for gravimetric determination . It forms a greenish-yellow precipitate with copper at a pH of 2.6 in the presence of acetic acid . Under these conditions, this is the only metal that precipitates; at pH 3.3, nickel also precipitates. Iron (III) will interfere. [ 2 ] It has been used as an ionophore in ion selective electrodes , with good response to Pb 2+ and Ni 2+ . [ 3 ]
Saloximes are used in the extraction and separation of metals from their ores. In one application of hydrometallurgy , Cu 2+ is extracted into organic solvents as its saloxime complex. [ 4 ] | https://en.wikipedia.org/wiki/Salicylaldoxime |
Salicylate testing is a category of drug testing that is focused on detecting salicylates such as acetysalicylic acid for either biochemical or medical purposes.
Salicylates can be identified by GC/MS , proton NMR , and IR . [ citation needed ]
One of the first in vitro tests for aspirin was through the Trinder reaction . Aqueous ferric chloride was added to a urine sample, and the formation of the iron complex turned the solution purple. [ citation needed ] This test was not specific to acetylsalicylic acid but would occur in the presence of any phenol or enol . The downfall of this test occurs in the presence of hyperbilirubinemia or elevated bilirubin . When the level of bilirubin exceeds 1 mg / dl , a false positive could occur. [ citation needed ]
The current in vitro testing utilizes molecule specific methods of detecting salicylates. [ 1 ]
Another identification mechanism is through immunoassay . Abbott Laboratories AxSYM is an immunoassay device utilizing Fluorescence Polarization Immunoassay (FPIA) technology that can determine the presence and quantify salicylates. The introduction of a salicylate specific antigen labeled with fluorescein into the sample will mark the sample. Upon irradiation with 490 nm light, some of that light will be reflected back to a detector at 520 nm . Polarization allows the machine to detect the difference between antibody bound, and unbound fluorescein. It is therefore possible to quantify the serum salicylate level through the signal strength—the amount of reflected light received. [ citation needed ] | https://en.wikipedia.org/wiki/Salicylate_testing |
Saline (also known as saline solution ) is a mixture of sodium chloride (salt) and water . [ 1 ] It has a number of uses in medicine including cleaning wounds, removal and storage of contact lenses , and help with dry eyes . [ 2 ] By injection into a vein , it is used to treat hypovolemia such as that from gastroenteritis and diabetic ketoacidosis . [ 2 ] [ 1 ] Large amounts may result in fluid overload , swelling , acidosis , and high blood sodium . [ 1 ] [ 2 ] In those with long-standing low blood sodium , excessive use may result in osmotic demyelination syndrome . [ 2 ]
Saline is in the crystalloid family of medications. [ 3 ] It is most commonly used as a sterile 9 g of salt per litre (0.9%) solution, known as normal saline . [ 1 ] Higher and lower concentrations may also occasionally be used. [ 4 ] [ 5 ] Saline is acidic, with a pH of 5.5 (due mainly to dissolved carbon dioxide). [ 6 ]
The medical use of saline began around 1831. [ 7 ] It is on the World Health Organization's List of Essential Medicines . [ 8 ] In 2022, sodium salts was the 216th most commonly prescribed medication in the United States, with more than 1 million prescriptions. [ 9 ] [ 10 ]
Normal saline ( NSS, NS or N/S ) is the commonly used phrase for a solution of 0.90% w/v of NaCl , 308 mOsm /L or 9.0 g per liter. Less commonly, this solution is referred to as physiological saline or isotonic saline (because it is approximately isotonic to blood serum, which makes it a physiologically normal solution). Although neither of those names is technically accurate because normal saline is not exactly like blood serum , they convey the practical effect usually seen: good fluid balance with minimal hypotonicity or hypertonicity. NS is used frequently in intravenous drips (IVs) for people who cannot take fluids orally and have developed or are in danger of developing dehydration or hypovolemia . NS is also used for aseptic purpose. NS is typically the first fluid used when hypovolemia is severe enough to threaten the adequacy of blood circulation, and has long been believed to be the safest fluid to give quickly in large volumes. However, it is now known that rapid infusion of NS can cause metabolic acidosis . [ 11 ]
The solution is 9 grams of sodium chloride (NaCl) dissolved in water, to a total volume of 1000 ml (weight per unit volume). The mass of 1 millilitre of normal saline is 1.0046 grams at 22 °C. [ 12 ] [ 13 ] The molecular weight of sodium chloride is approximately 58.4 grams per mole, so 58.4 grams of sodium chloride equals 1 mole. Since normal saline contains 9 grams of NaCl, the concentration is 9 grams per litre divided by 58.4 grams per mole, or 0.154 mole per litre. Since NaCl dissociates into two ions – sodium and chloride – 1 molar NaCl is 2 osmolar. Thus, NS contains 154 mEq /L of Na + and the same amount of Cl − . This points to an osmolarity of 154 + 154 = 308, which is higher (i.e. more solute per litre) than that of blood (approximately 285). [ 14 ] However, if the osmotic coefficient (a correction for non-ideal solutions) is taken into account, then the saline solution is much closer to isotonic. The osmotic coefficient of NaCl is about 0.93, [ 15 ] which yields an osmolarity of 0.154 × 1000 × 2 × 0.93 = 286.44. Therefore, the osmolarity of normal saline is a close approximation to the osmolarity of blood.
For medical purposes, saline is often used to flush wounds and skin abrasions . However, research indicates that it is no more effective than potable tap water. [ 16 ] Normal saline will not burn or sting when applied. [ citation needed ]
Saline is also used in I.V. therapy , intravenously supplying extra water to rehydrate people or supplying the daily water and salt needs ("maintenance" needs) of a person who is unable to take them by mouth. Because infusing a solution of low osmolality can cause problems such as hemolysis , intravenous solutions with reduced saline concentrations (less than 0.9%) typically have dextrose ( glucose ) added to maintain a safe osmolality while providing less sodium chloride. The amount of normal saline infused depends largely on the needs of the person (e.g. ongoing diarrhea or heart failure ). [ citation needed ]
Saline is also often used for nasal washes to relieve some of the symptoms of rhinitis and the common cold . [ 17 ] The solution exerts a softening and loosening influence on the mucus to make it easier to wash out and clear the nasal passages for both babies [ 18 ] and adults. [ 19 ] In very rare instances, fatal infection by the amoeba Naegleria fowleri can occur if it enters the body through the nose; therefore tap water must not be used for nasal irrigation. Water is only appropriate for this purpose if it is sterile, distilled, boiled, filtered, or disinfected. [ 20 ]
Sterile isotonic saline is also used to fill breast implants for use in breast augmentation surgery, to correct congenital abnormalities such as tuberous breast deformity, and to correct breast asymmetry. [ 21 ] [ 22 ] Saline breast implants are also used in reconstructive surgery post-mastectomy.
Eye drops are saline-containing drops used on the eye . Depending on the condition being treated, they may contain steroids , antihistamines , sympathomimetics , beta receptor blockers , parasympathomimetics , parasympatholytics , prostaglandins , non-steroidal anti-inflammatory drugs (NSAIDs), antibiotics or topical anesthetics . Eye drops sometimes do not have medications in them and are only lubricating and tear -replacing solutions.
There is tentative evidence that saline nasal irrigation may help with long term cases of rhinosinusitis . [ 23 ] Evidence for use in cases of rhinosinusitis of short duration is unclear. [ 24 ]
Saline is used in scleral tattooing , coloring the white part of the human eye. [ 25 ]
Saline is used to lighten tattoos (including microblading tattoos) through the process of osmosis . [ 26 ]
Concentrations lower and higher than normal also exist. High concentrations are used rarely in medicine but frequently in molecular biology .
Hypertonic saline—7% NaCl solutions are considered mucoactive agents and thus are used to hydrate thick secretions ( mucus ) in order to make it easier to cough up and out ( expectorate ). 3% hypertonic saline solutions are also used in critical care settings, acutely increased intracranial pressure , or severe hyponatremia . [ 27 ] Inhalation of hypertonic saline has also been shown to help in other respiratory problems, specifically bronchiolitis . [ 28 ] Hypertonic saline is currently recommended by the Cystic Fibrosis Foundation as a primary part of a cystic fibrosis treatment regimen. [ 29 ]
An 11% solution of xylitol with 0.65% saline stimulates the washing of the nasopharynx and has an effect on the nasal pathogenic bacteria. This has been used in complementary and alternative medicine. [ 30 ]
Hypertonic saline may be used in perioperative fluid management protocols to reduce excessive intravenous fluid infusions and lessen pulmonary complications. [ 31 ] Hypertonic saline is used in treating hyponatremia and cerebral edema . Rapid correction of hyponatremia via hypertonic saline, or via any saline infusion > 40 mmol/L (Na+ having a valence of 1, 40 mmol/L = 40 mEq/L) greatly increases risk of central pontine myelinolysis (CPM), and so requires constant monitoring of the person's response. Water privation combined with diuretic block does not produce as much risk of CPM as saline administration does; however, it does not correct hyponatremia as rapidly as administration of hypertonic saline does. Due to hypertonicity, administration may result in phlebitis and tissue necrosis . As such, concentrations greater than 3% NaCl should normally be administered via a central venous catheter , also known as a 'central line'. Such hypertonic saline is normally available in two strengths, the former of which is more commonly administered:
Hypertonic NaCl solutions that are less commonly used are 7% (1200 mEq/L) and 23.4% (approx 4000 mEq/L), both of which are used (also via central line), often in conjunction with supplementary diuretics, in the treatment of traumatic brain injury . [ 32 ]
Other concentrations commonly used include:
In medicine, common types of salines include:
And in cell biology, in addition to the above the following are used:
Saline was believed to have originated during the Indian Blue cholera pandemic that swept across Europe in 1831. William Brooke O'Shaughnessy , a recent graduate of Edinburgh Medical School , proposed in an article to medical journal The Lancet to inject people infected with cholera with highly oxygenated salts to treat the "universal stagnation of the venous system and rapid cessation of arterialisation of the blood" seen in people with severely dehydrated cholera. [ 33 ] He found his treatment harmless in dogs, and his proposal was soon adopted by the physician Thomas Latta in treating people with cholera to beneficial effect. In the following decades, variations and alternatives to Latta's solution were tested and used in treating people with cholera. These solutions contained a range of concentrations of sodium, chloride, potassium, carbonate, phosphate, and hydroxide.
The breakthrough in achieving physiological concentrations was accomplished by Sydney Ringer in the early 1880s, [ 34 ] when he determined the optimal salt concentrations to maintain the contractility of frog heart muscle tissue. Normal saline is considered a descendant of the pre-Ringer solutions, as Ringer's findings were not adopted and widely used until decades later. The term "normal saline" itself appears to have little historical basis, except for studies done in 1882–83 by Dutch physiologist Hartog Jacob Hamburger ; these in vitro studies of red cell lysis suggested incorrectly that 0.9% was the concentration of salt in human blood (rather than 0.6%, the true concentration). [ 35 ]
Normal saline has become widely used in modern medicine, but due to the mismatch with real blood, other solutions have proved better. The 2018 publication of a randomized, controlled trial with 15,000 people in intensive care units showed that compared to normal saline, lactated Ringer's solution reduced the combined risk of mortality, need for additional dialysis, or persistent kidney problems from 15% to 14%, which given the large number of patients is a significant reduction. [ 36 ]
Coconut water has been used in place of normal saline in areas without access to normal saline. [ 37 ] Its use, however, has not been well studied. [ 37 ] | https://en.wikipedia.org/wiki/Saline_(medicine) |
Salinity ( / s ə ˈ l ɪ n ɪ t i / ) is the saltiness or amount of salt dissolved in a body of water , called saline water (see also soil salinity ). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal to ‰ ).
Salinity is an important factor in determining many aspects of the chemistry of natural waters and of biological processes within it, and is a thermodynamic state variable that, along with temperature and pressure , governs physical characteristics like the density and heat capacity of the water.
A contour line of constant salinity is called an isohaline , or sometimes isohale .
Salinity in rivers, lakes, and the ocean is conceptually simple, but technically challenging to define and measure precisely. Conceptually the salinity is the quantity of dissolved salt content of the water. Salts are compounds like sodium chloride , magnesium sulfate , potassium nitrate , and sodium bicarbonate which dissolve into ions. The concentration of dissolved chloride ions is sometimes referred to as chlorinity. Operationally, dissolved matter is defined as that which can pass through a very fine filter (historically a filter with a pore size of 0.45 μm, but later [ when? ] usually 0.2 μm). [ 2 ] Salinity can be expressed in the form of a mass fraction , i.e. the mass of the dissolved material in a unit mass of solution.
Seawater typically has a mass salinity of around 35 g/kg, although lower values are typical near coasts where rivers enter the ocean. Rivers and lakes can have a wide range of salinities, from less than 0.01 g/kg [ 3 ] to a few g/kg, although there are many places where higher salinities are found. The Dead Sea has a salinity of more than 200 g/kg. [ 4 ] Precipitation typically has a TDS of 20 mg/kg or less. [ 5 ]
Whatever pore size is used in the definition, the resulting salinity value of a given sample of natural water will not vary by more than a few percent (%). Physical oceanographers working in the abyssal ocean , however, are often concerned with precision and intercomparability of measurements by different researchers, at different times, to almost five significant digits . [ 6 ] A bottled seawater product known as IAPSO Standard Seawater is used by oceanographers to standardize their measurements with enough precision to meet this requirement.
Measurement and definition difficulties arise because natural waters contain a complex mixture of many different elements from different sources (not all from dissolved salts) in different molecular forms. The chemical properties of some of these forms depend on temperature and pressure. Many of these forms are difficult to measure with high accuracy, and in any case complete chemical analysis is not practical when analyzing multiple samples. Different practical definitions of salinity result from different attempts to account for these problems, to different levels of precision, while still remaining reasonably easy to use.
For practical reasons salinity is usually related to the sum of masses of a subset of these dissolved chemical constituents (so-called solution salinity ), rather than to the unknown mass of salts that gave rise to this composition (an exception is when artificial seawater is created). For many purposes this sum can be limited to a set of eight major ions in natural waters, [ 7 ] [ 8 ] although for seawater at highest precision an additional seven minor ions are also included. [ 6 ] The major ions dominate the inorganic composition of most (but by no means all) natural waters. Exceptions include some pit lakes and waters from some hydrothermal springs .
The concentrations of dissolved gases like oxygen and nitrogen are not usually included in descriptions of salinity. [ 2 ] However, carbon dioxide gas, which when dissolved is partially converted into carbonates and bicarbonates , is often included. Silicon in the form of silicic acid , which usually appears as a neutral molecule in the pH range of most natural waters, may also be included for some purposes (e.g., when salinity/density relationships are being investigated).
The term salinity is, for oceanographers, usually associated with one of a set of specific measurement techniques. As the dominant techniques evolve, so do different descriptions of salinity. Salinities were largely measured using titration -based techniques before the 1980s. Titration with silver nitrate could be used to determine the concentration of halide ions (mainly chlorine and bromine ) to give a chlorinity . The chlorinity was then multiplied by a factor to account for all other constituents. The resulting 'Knudsen salinities' are expressed in units of parts per thousand (ppt or ‰ ).
The use of electrical conductivity measurements to estimate the ionic content of seawater led to the development of the scale called the practical salinity scale 1978 (PSS-78). [ 9 ] [ 10 ] Salinities measured using PSS-78 do not have units. The suffix psu or PSU (denoting practical salinity unit ) is sometimes added to PSS-78 measurement values. [ 11 ] The addition of PSU as a unit after the value is "formally incorrect and strongly discouraged". [ 2 ]
In 2010 a new standard for the properties of seawater called the thermodynamic equation of seawater 2010 ( TEOS-10 ) was introduced, advocating absolute salinity as a replacement for practical salinity, and conservative temperature as a replacement for potential temperature . [ 6 ] This standard includes a new scale called the reference composition salinity scale . Absolute salinities on this scale are expressed as a mass fraction, in grams per kilogram of solution. Salinities on this scale are determined by combining electrical conductivity measurements with other information that can account for regional changes in the composition of seawater. They can also be determined by making direct density measurements.
A sample of seawater from most locations with a chlorinity of 19.37 ppt will have a Knudsen salinity of 35.00 ppt, a PSS-78 practical salinity of about 35.0, and a TEOS-10 absolute salinity of about 35.2 g/kg. The electrical conductivity of this water at a temperature of 15 °C is 42.9 mS/cm. [ 6 ] [ 12 ]
On the global scale, it is extremely likely that human-caused climate change has contributed to observed surface and subsurface salinity changes since the 1950s, and projections of surface salinity changes throughout the 21st century indicate that fresh ocean regions will continue to get fresher and salty regions will continue to get saltier. [ 13 ]
Salinity is serving as a tracer of different masses. Surface water is pulled in to replace the sinking water, which in turn eventually becomes cold and salty enough to sink. Salinity distribution contributes to shape the oceanic circulation.
Limnologists and chemists often define salinity in terms of mass of salt per unit volume, expressed in units of mg/L or g/L. [ 7 ] It is implied, although often not stated, that this value applies accurately only at some reference temperature because solution volume varies with temperature. Values presented in this way are typically accurate to the order of 1%. Limnologists also use electrical conductivity , or "reference conductivity", as a proxy for salinity. This measurement may be corrected for temperature effects, and is usually expressed in units of μS/cm .
A river or lake water with a salinity of around 70 mg/L will typically have a specific conductivity at 25 °C of between 80 and 130 μS/cm. The actual ratio depends on the ions present. [ 14 ] The actual conductivity usually changes by about 2% per degree Celsius, so the measured conductivity at 5 °C might only be in the range of 50–80 μS/cm.
Direct density measurements are also used to estimate salinities, particularly in highly saline lakes . [ 4 ] Sometimes density at a specific temperature is used as a proxy for salinity. At other times an empirical salinity/density relationship developed for a particular body of water is used to estimate the salinity of samples from a measured density.
Marine waters are those of the ocean, another term for which is euhaline seas . The salinity of euhaline seas is 30 to 35 ‰. Brackish seas or waters have salinity in the range of 0.5 to 29 ‰ and metahaline seas from 36 to 40 ‰. These waters are all regarded as thalassic because their salinity is derived from the ocean and defined as homoiohaline if salinity does not vary much over time (essentially constant). The table on the right, modified from Por (1972), [ 15 ] [ 16 ] follows the "Venice system" (1959). [ 17 ]
In contrast to homoiohaline environments are certain poikilohaline environments (which may also be thalassic ) in which the salinity variation is biologically significant. [ 18 ] Poikilohaline water salinities may range anywhere from 0.5 to greater than 300 ‰. The important characteristic is that these waters tend to vary in salinity over some biologically meaningful range seasonally or on some other roughly comparable time scale. Put simply, these are bodies of water with quite variable salinity.
Highly saline water, from which salts crystallize (or are about to), is referred to as brine .
Salinity is an ecological factor of considerable importance, influencing the types of organisms that live in a body of water. As well, salinity influences the kinds of plants that will grow either in a water body, or on land fed by a water (or by a groundwater ). [ 19 ] A plant adapted to saline conditions is called a halophyte . A halophyte which is tolerant to residual sodium carbonate salinity are called glasswort or saltwort or barilla plants. Organisms (mostly bacteria) that can live in very salty conditions are classified as extremophiles , or halophiles specifically. An organism that can withstand a wide range of salinities is euryhaline .
Salts are expensive to remove from water, and salt content is an important factor in water use, factoring into potability and suitability for irrigation . Increases in salinity have been observed in lakes and rivers in the United States, due to common road salt and other salt de-icers in runoff. [ 20 ]
The degree of salinity in oceans is a driver of the world's ocean circulation , where density changes due to both salinity changes and temperature changes at the surface of the ocean produce changes in buoyancy, which cause the sinking and rising of water masses. Changes in the salinity of the oceans are thought to contribute to global changes in carbon dioxide as more saline waters are less soluble to carbon dioxide. In addition, during glacial periods, the hydrography is such that a possible cause of reduced circulation is the production of stratified oceans. In such cases, it is more difficult to subduct water through the thermohaline circulation.
Not only is salinity a driver of ocean circulation, but changes in ocean circulation also affect salinity, particularly in the subpolar North Atlantic where from 1990 to 2010 increased contributions of Greenland meltwater were counteracted by increased northward transport of salty Atlantic waters. [ 13 ] [ 21 ] [ 22 ] [ 23 ] However, North Atlantic waters have become fresher since the mid-2010s due to increased Greenland meltwater flux. [ 13 ] [ 24 ] | https://en.wikipedia.org/wiki/Salinity |
A salinometer is a device designed to measure the salinity , or dissolved salt content, of a solution .
Since the salinity affects both the electrical conductivity and the specific gravity of a solution, a salinometer often consist of an ec meter or hydrometer and some means of converting those readings to a salinity reading. A salinometer may be calibrated in either micromhos , a unit of electrical conductivity , (usually 0-22) or else directly calibrated for salt in 'grains per gallon' (0-0.5). [ 1 ] A typical reading on-board ship would be 2 micromhos or 0.05 grains per gallon. A reading of twice this may trigger a warning light or alarm. [ 1 ]
Fresh water generators ( Evaporators ) use salinometers on the distillate discharge in order to gauge the quality of the water. Water from the evaporator can be destined for potable water supplies, so salty water is not desirable for human consumption.
In some ships, extremely high quality distillate is required for use in water-tube boilers, where salt water would be disastrous. In these ships, a salinometer is also installed on the feed system where it would alert the engineer to any salt contamination. The salinometer may switch the evaporator's output from fresh-water to feed-water tanks automatically, depending on the water quality. [ 2 ] The higher quality (lower salinity) is required for the boiler feedwater , not for drinking.
This standards - or measurement -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Salinometer |
The salinosporamides are a group of closely related chemical compounds isolated from marine bacteria in the genus Salinispora . [ 1 ] [ 2 ] [ 3 ] [ 4 ] They possess a densely functionalized γ-lactam-β-lactone bicyclic core .
Salinosporamide A has attracted interest for its potential use in treating various types of cancer. [ 5 ] [ 6 ] [ 7 ] [ 8 ]
In addition, a variety of synthetic analogs have been prepared. [ 9 ] | https://en.wikipedia.org/wiki/Salinosporamide |
Salinosporamide A ( Marizomib ) is a potent proteasome inhibitor being studied as a potential anticancer agent . It entered phase I human clinical trials for the treatment of multiple myeloma , only three years after its discovery in 2003. [ 1 ] [ 2 ] This marine natural product is produced by the obligate marine bacteria Salinispora tropica and Salinispora arenicola , which are found in ocean sediment . Salinosporamide A belongs to a family of compounds, known collectively as salinosporamides , which possess a densely functionalized γ-lactam-β-lactone bicyclic core .
Salinosporamide A was discovered by William Fenical and Paul Jensen from Scripps Institution of Oceanography in La Jolla, CA. In preliminary screening, a high percentage of the organic extracts of cultured Salinispora strains possessed antibiotic and anticancer activities, which suggests that these bacteria are an excellent resource for drug discovery. Salinispora strain CNB-392 was isolated from a heat-treated marine sediment sample and cytotoxicity-guided fractionation of the crude extract led to the isolation of salinosporamide A. Although salinosporamide A shares an identical bicyclic ring structure with omuralide , it is uniquely functionalized. Salinosporamide A displayed potent in vitro cytotoxicity against HCT-116 human colon carcinoma with an IC50 value of 11 ng mL-1. This compound also displayed potent and highly selective activity in the NCI's 60-cell-line panel with a mean GI50 value (the concentration required to achieve 50% growth inhibition) of less than 10 nM and a greater than 4 log LC50 differential between resistant and susceptible cell lines. The greatest potency was observed against NCI-H226 non-small cell lung cancer, SF-539 brain tumor, SK-MEL-28 melanoma, and MDA-MB-435 melanoma (formerly misclassified as breast cancer [ 3 ] ), all with LC50 values less than 10 nM. Salinosporamide A was tested for its effects on proteasome function because of its structural relationship to omuralide. When tested against purified 20S proteasome, salinosporamide A inhibited proteasomal chymotrypsin-like proteolytic activity with an IC50 value of 1.3 nM. [ 4 ] This compound is approximately 35 times more potent than omuralide which was tested as a positive control in the same assay. Thus, the unique functionalization of the core bicyclic ring structure of salinosporamide A appears to have resulted in a molecule that is a significantly more potent proteasome inhibitor than omuralide. [ 1 ]
Salinosporamide A inhibits proteasome activity by covalently modifying the active site threonine residues of the 20S proteasome. [ citation needed ]
It was originally hypothesized that salinosporamide B was a biosynthetic precursor to salinosporamide A due to their structural similarities. [ citation needed ]
It was thought that the halogenation of the unactivated methyl group was catalyzed by a non-heme iron halogenase. [ 5 ] [ 6 ] Recent work using 13 C -labeled feeding experiments reveal distinct biosynthetic origins of salinosporamide A and B. [ 5 ] [ 7 ]
While they share the biosynthetic precursors acetate and presumed β-hydroxycyclohex-2'-enylalanine ( 3 ), they differ in the origin of the four-carbon building block that gives rise to their structural differences involving the halogen atom. A hybrid polyketide synthase -nonribosomal peptide synthetase (PKS-NRPS) pathway is most likely the biosynthetic mechanism in which acetyl-CoA and butyrate-derived ethylmalonyl-CoA condense to yield the β-ketothioester ( 4 ), which then reacts with ( 3 ) to generate the linear precursor ( 5 ).
The first stereoselective synthesis was reported by Rajender Reddy Leleti and E. J.Corey. [ 8 ] Later several routes to the total synthesis of salinosporamide A have been reported. [ 8 ] [ 9 ] [ 10 ] [ 11 ]
In vitro studies using purified 20S proteasomes showed that salinosporamide A has lower EC50 for trypsin-like (T-L) activity than does bortezomib . In vivo animal model studies show marked inhibition of T-L activity in response to salinosporamide A, whereas bortezomib enhances T-L proteasome activity.
Initial results from early-stage clinical trials of salinosporamide A in relapsed/refractory multiple myeloma patients were presented at the 2011 American Society of Hematology annual meeting. [ 12 ] Further early-stage trials of the drug in a number of different cancers are ongoing. [ 13 ] | https://en.wikipedia.org/wiki/Salinosporamide_A |
Saliva (commonly referred to as spit or drool ) is an extracellular fluid produced and secreted by salivary glands in the mouth . In humans , saliva is around 99% water , plus electrolytes , mucus , white blood cells , epithelial cells (from which DNA can be extracted), enzymes (such as lingual lipase and amylase ), and antimicrobial agents (such as secretory IgA , and lysozymes ). [ 1 ]
The enzymes found in saliva are essential in beginning the process of digestion of dietary starches and fats. These enzymes also play a role in breaking down food particles entrapped within dental crevices, thus protecting teeth from bacterial decay. [ 2 ] Saliva also performs a lubricating function, wetting food and permitting the initiation of swallowing , and protecting the oral mucosa from drying out . [ 3 ]
Saliva has specialized purposes for a variety of animal species beyond predigestion. Certain swifts construct nests with their sticky saliva. The foundation of bird's nest soup is an aerodramus nest. Venomous saliva injected by fangs is used by cobras, vipers, and certain other members of the venom clade to hunt. Some caterpillars use modified salivary glands to store silk proteins, which they then use to make silk fiber. [ 4 ]
Produced in salivary glands , human saliva comprises 99.5% water, but also contains many important substances, including electrolytes , mucus , antibacterial compounds and various enzymes . [ 1 ] Medically, constituents of saliva can noninvasively provide important diagnostic information related to oral and systemic diseases. [ 5 ]
Experts debate the amount of saliva that a healthy person produces. Production is estimated at 1,500 mL per day and researchers generally accept that during sleep the amount drops significantly. [ 3 ] [ 9 ] In humans, the submandibular gland contributes around 70 to 75% of secretions, while the parotid gland secretes about 20 to 25%; small amounts are secreted from the other salivary glands. [ 10 ]
Via the action of amylase and other enzymes, saliva contributes to the digestion of food and to the maintenance of oral hygiene. [ 11 ] Saliva limits the growth of bacterial pathogens and is a major factor in sustaining systemic and oral health through the prevention of tooth decay. [ 11 ] Saliva also acts as a buffer, reducing acidity of food components by its bicarbonate and phosphate content. [ 11 ]
Saliva coats the oral mucosa , mechanically protecting it from trauma during eating, swallowing, and speaking. Mouth soreness is common in people with reduced saliva ( xerostomia ) and food (especially dry food) sticks to the inside of the mouth. [ 11 ]
The digestive functions of saliva include moistening food and helping to create a food bolus . The lubricative function of saliva allows the food bolus to be passed easily from the mouth into the esophagus. Saliva contains the enzyme amylase, also called ptyalin, which is capable of breaking down starch into simpler sugars such as maltose and dextrin that can be further broken down in the small intestine. [ 11 ] About 30% of starch digestion takes place in the mouth cavity. Salivary glands also secrete salivary lipase to begin fat digestion. Salivary lipase plays a large role in fat digestion in newborn infants as their pancreatic lipase still needs some time to develop. [ 12 ]
Saliva has a role in the sense of taste . [ 11 ] It is the liquid medium in which chemicals are carried to taste receptor cells (mostly associated with lingual papillae ). [ 11 ] People with little saliva may experience dysgeusia (reduced ability to taste or to experience a metallic taste), occurring as an adverse effect of some prescription drugs . [ 13 ]
Saliva can be used in development of non-invasive biomarkers to diagnose the presence or risk of some diseases, such as dental caries and periodontal disease . [ 5 ] [ 14 ] [ 15 ]
The production of saliva is stimulated both by the sympathetic nervous system and the parasympathetic . [ 19 ]
Sympathetic stimulation of saliva is to facilitate respiration , whereas parasympathetic stimulation is to facilitate digestion.
Parasympathetic stimulation leads to acetylcholine (ACh) release onto the salivary acinar cells. ACh binds to muscarinic receptors , specifically M 3 , and causes an increased intracellular calcium ion concentration (through the IP 3 /DAG second messenger system). Increased calcium causes vesicles within the cells to fuse with the apical cell membrane leading to secretion. ACh also causes the salivary gland to release kallikrein , an enzyme that converts kininogen to lysyl-bradykinin . Lysyl-bradykinin acts upon blood vessels and capillaries of the salivary gland to generate vasodilation and increased capillary permeability , respectively. The resulting increased blood flow to the acini allows the production of more saliva. In addition, Substance P can bind to Tachykinin NK-1 receptors leading to increased intracellular calcium concentrations and subsequently increased saliva secretion. Lastly, both parasympathetic and sympathetic nervous stimulation can lead to myoepithelium contraction which causes the expulsion of secretions from the secretory acinus into the ducts and eventually to the oral cavity.
Sympathetic stimulation results in the release of norepinephrine . Norepinephrine binding to α-adrenergic receptors will cause an increase in intracellular calcium levels leading to more fluid vs. protein secretion. If norepinephrine binds β-adrenergic receptors, it will result in more protein or enzyme secretion vs. fluid secretion. Stimulation by norepinephrine initially decreases blood flow to the salivary glands due to constriction of blood vessels but this effect is overtaken by vasodilation caused by various local vasodilators.
Saliva production may also be pharmacologically stimulated by the so-called sialagogues . It can also be suppressed by the so-called antisialagogues .
Spitting is the act of forcibly ejecting saliva or other substances from the mouth. In many parts of the world, it is considered rude and a social taboo , and has sometimes been outlawed. In some countries, for example, it has been outlawed for reasons of public decency and attempting to reduce the spread of disease. These laws may not strictly enforced, but in Singapore , the fine for spitting may be as high as SGD$2,000 for multiple offenses, and one can even be arrested. [ citation needed ] In China , expectoration is more socially acceptable (even if officially disapproved of or illegal), and spittoons are still a common appearance in some cultures. Some animals, even humans in some cases, use spitting as an automatic defensive maneuver. Camels are well known for doing this, though most domestic camels are trained not to.
Spitting by an infected person (for example, one with SARS-CoV-2 ) whose saliva contains large amounts of virus , [ 14 ] is a health hazard to the public.
Many birds in the swift family, Apodidae, produce a viscous saliva during nesting season to glue together materials to construct a nest. [ 20 ] Two species of swifts in the genus Aerodramus build their nests using only their saliva , the base for bird's nest soup . [ 21 ]
A common belief is that saliva contained in the mouth has natural disinfectants , which leads people to believe it is beneficial to " lick their wounds ". Researchers at the University of Florida at Gainesville have discovered a protein called nerve growth factor (NGF) in the saliva of mice . Wounds doused with NGF healed twice as fast as untreated and unlicked wounds; therefore, saliva can help to heal wounds in some species. NGF has been found in human saliva, as well as antibacterial agents as secretory mucin , IgA , lactoferrin , lysozyme and peroxidase . [ 22 ] [ 23 ] It has not been shown that human licking of wounds disinfects them, but licking is likely to help clean the wound by removing larger contaminants such as dirt and may help to directly remove infective bodies by brushing them away. Therefore, licking would be a way of wiping off pathogens, useful if clean water is not available to the animal or person.
In Pavlov's experiment, dogs were conditioned to salivate in response to a ringing bell; this stimulus is associated with a meal or hunger . Salivary secretion is also associated with nausea . Saliva is usually formed in the mouth through an act called gleeking , which can be voluntary or involuntary.
Some old cultures use chewed grains to produce alcoholic beverages, such as chicha , kasiri or sake .
Commercially available saliva substitutes exist. [ 24 ] | https://en.wikipedia.org/wiki/Saliva |
The salivary microbiome consists of the nonpathogenic , commensal bacteria present in the healthy human salivary glands . It differs from the oral microbiome which is located in the oral cavity. Oral microorganisms tend to adhere to teeth. [ 1 ] The oral microbiome possesses its own characteristic microorganisms found there. Resident microbes of the mouth adhere to the teeth and gums. "[T]here may be important interactions between the saliva microbiome and other microbiomes in the human body, in particular, that of the intestinal tract." [ 2 ]
Unlike the uterine , placental and vaginal microbiomes , the types of organisms in the salivary microbiota remain relatively constant. There is no difference between populations of microbes based upon gender , age, diet , obesity , alcohol intake, race, or tobacco use . [ 3 ] The salivary microbiome characteristically remains stable over a lifetime. [ 4 ] One study suggests sharing an environment (e.g., living together) may influence the salivary microbiome more than genetic components. [ 4 ] Porphyromonas , Solobacterium , Haemophilus , Corynebacterium , Cellulosimicrobium , Streptococcus and Campylobacter are some of the genera found in the saliva . [ 5 ]
While the salivary microbiome shows stability, the broader oral microbiome can be influenced by various factors. A number of elements, including diet, dental hygiene, age, underlying medical conditions, and the use of antibiotics, as well as lifestyle choices such as smoking and alcohol consumption, and physiological changes such as pregnancy, the menstrual cycle, and menopause, can exert an influence on the composition of the oral microbiome. [ 6 ] [ 7 ] [ 8 ]
"There is high diversity in the salivary microbiome within and between individuals, but little geographic structure. Overall, ~13.5% of the total variance in the composition of genera is due to differences among individuals, which is remarkably similar to the fraction of the total variance in neutral genetic markers that can be attributed to differences among human populations." [ 2 ]
"[E]nvironmental variables revealed a significant association between the genetic distances among locations and the distance of each location from the equator. Further characterization of the enormous diversity revealed here in the human salivary microbiome will aid in elucidating the role it plays in human health and disease, and in the identification of potentially informative species for studies of human population history." [ 2 ]
Sixty new genera have been identified from the salivary glands. A total of 101 different genera were identified in the salivary glands. Out of these, 39 genera are not found in the oral microbiome. It is not known whether the resident species remain constant or change. [ 2 ]
Though the association between the salivary microbiome is similar to that of the oral microbiome, there also exists an association the salivary microbiome and the gut microbiome . Saliva sampling may be a non-invasive way to detect changes in the gut microbiome and changes in systemic disease . The association between the salivary microbiome those with Polycistic Ovarian Syndrome has been characterized: "saliva microbiome profiles correlate with those in the stool, despite the fact that the bacterial communities in the two locations differ greatly. Therefore, saliva may be a useful alternative to stool as an indicator of bacterial dysbiosis in systemic disease." [ 9 ]
The sugar concentration in salivary secretions can vary. Blood sugar levels are reflected in salivary gland secretions. High salivary glucose (HSG) levels are a glucose concentration ≥ 1.0 mg/d, n = 175) and those with low salivary glucose (LSG) levels are < 0.1 mg/dL n = 2,537). Salivary gland secretions containing high levels of sugar change the oral microbiome and contributes to an environment that is conductive to the formation of dental caries and gingivitis. [ 10 ]
Organisms of the salivary microbiome reside in the three major salivary glands : parotid , submandibular , and sublingual . These glands secrete electrolytes , proteins , genetic material, polysaccharides , and other molecules. Most of these substances enter the salivary gland acinus and duct system from surrounding capillaries via the intervening tissue fluid, although some substances are produced within the glands themselves. The level of each salivary component varies considerably depending on the health status of the individual and the presence of pathogenic and commensal organisms. | https://en.wikipedia.org/wiki/Salivary_microbiome |
Sally Anne Brooker MNZM is a New Zealand inorganic chemist . She has been a full professor at the University of Otago since 2006. [ 1 ] [ 2 ] [ 3 ]
Brooker was educated at Hawarden Area School in North Canterbury from 1970 to 1982, [ 4 ] and was dux of the school in her final year there. [ 5 ] She went on to study chemistry at the University of Canterbury , first graduating Bachelor of Science with first-class honours, and then completing a PhD titled Synthesis and characterisation of polynuclear complexes with macrocyclic and related ligands under the supervision of Vickie McKee in 1989. [ 4 ] [ 6 ]
After a period of post-doctoral research with George Sheldrick at the University of Göttingen , Brooker returned to New Zealand to take up a lectureship in chemistry at the University of Otago in 1991. [ 4 ] [ 7 ] She rose to become a full professor in 2006. [ 7 ]
Brooker's research is in the fields of transition-metal and macrocyclic chemistry. [ 2 ] Her work has included the development of molecular switches and molecular magnets , with potential application in nanodevices . [ 8 ]
In the 2017 Queen's Birthday Honours , Brooker was appointed a Member of the New Zealand Order of Merit , for services to science. [ 9 ] [ 10 ] Later that year, she won the Hector Medal from the Royal Society of New Zealand . [ 8 ] [ 11 ] [ 12 ] Also in 2017, Brooker was selected as one of the Royal Society Te Apārangi's " 150 women in 150 words ", celebrating the contributions of women to knowledge in New Zealand. [ 13 ]
Brooker was elected a Fellow of the Royal Society of New Zealand in 2007, and a Fellow of the Royal Society of Chemistry in 2011. [ 8 ] She is also a Fellow of the New Zealand Institute of Chemistry. [ 4 ] In October 2019, Brooker was appointed one of seven inaugural sesquicentennial distinguished chairs, or poutoko taiea , at Otago University. [ 14 ] She was awarded the University's Distinguished Research Medal in 2015. [ 15 ] | https://en.wikipedia.org/wiki/Sally_Brooker |
Sally hashim Shlaer (December 3, 1938 – November 12, 1998) was an American mathematician , software engineer and software methodologist , [ 1 ] known as co-developer of the 1980s Shlaer–Mellor method for software development.
Born in Cleveland, Ohio , Shlaer received a BS in Mathematics in 1960 from Stanford University and started a graduate study at the Australian National University .
At Stanford Shlaer had started programming in Fortran and assembler . In 1965 she started as a software engineer at Los Alamos National Laboratory . In 1977 she became project manager in software development at Lawrence Berkeley Laboratory , where she guided the development of a new Integrated Control System for the Bay Area Rapid Transit system. [ 1 ]
At Lawrence Berkeley, Laboratory Shlaer met Stephen J. Mellor , with whom she developed the Shlaer–Mellor method for software development. In 1985 together they founded the software development firm Project Technology Inc. Shlaer was also a Fellows of the Association for Computing Machinery .
Shlaer started her software engineering career at Los Alamos National Laboratory as a programmer. She designed and implemented an operating system to operate an electron accelerator to work in real time, and this project became her masterpiece. [ 2 ]
At Lawrence Berkeley Laboratory, she led a team of software developers to build a new control system for the subway of the Bay Area Rapid Transit system. The existing control system software was considered impossible to continue using, making replacement necessary. Working with Steve Mellor, they replaced the original Fortran and assembly language code with new code, going from seventy thousand lines to two thousand. This analysis has since been called "legendary". [ 2 ]
In the developing of a new control system for the Bay Area Rapid Transit, Shlaer and Mellor sought to regulate mechanisms of software development and began to design new methods of project management . [ 2 ] This resulted in the development of the Shlaer–Mellor method , which in the new millennium has evolved into Executable UML . [ 3 ]
Articles, a selection: [ 4 ] | https://en.wikipedia.org/wiki/Sally_Shlaer |
A salmon run is an annual fish migration event where many salmonid species, which are typically hatched in fresh water and live most of their adult life downstream in the ocean , swim back against the stream to the upper reaches of rivers to spawn on the gravel beds of small creeks . After spawning, most Atlantic salmon [ 1 ] and all species of Pacific salmon [ citation needed ] die, and the salmon life cycle starts over again with the new generation of hatchlings .
Salmon are anadromous , spending their juvenile life in rivers or lakes, and then migrating out to sea where they spend adult lives and gain most of their body mass . When they reach sexual maturity , the adults return to the upstream rivers to reproduce . Usually they return with uncanny precision to the natal river where they were born, and even to the very spawning ground of their birth. It is thought that, when they are in the ocean, they use magnetoreception to locate the general position of their natal river, and once close to the river, that they use their sense of smell to home in on the river entrance and even their natal spawning ground.
Trout , which are sister species of salmon, also perform similar migrations, although they mostly move potamodromously between creeks and large freshwater lakes, except for some coastal/ estuary subspecies such as steelhead and sea trout that migrate seasonally between salty / brackish and fresh water just like salmon do. There are also landlocked populations of some salmon species that have adapted to spend their entire life in freshwater like trout.
In Northwest America , salmons are keystone species , which means the ecological impact they have on other wildlife is greater than would be expected in relation to their biomass . Most salmon species migrate during the autumn (September through November), [ 2 ] which coincides with the pre- winter activities of many hibernating animals. The annual salmon run can be a major feeding event for predators such as grizzly bears and bald eagles , as well as an important window period for sport fishermen .
The post-spawning death of salmon also has important ecological consequences, because the significant nutrients in their carcasses , rich in nitrogen , sulfur , carbon and phosphorus , are transferred from the ocean and released to inland aquatic ecosystems , terrestrial animals (such as bears) and the wetlands and riparian woodlands adjacent to the rivers. This has knock-on effects not only for the next generation of salmon, but to every wildlife species living in the riparian zones the salmon reach. [ 3 ] The nutrients can also be washed downstream into estuaries where they accumulate and provide significant support for invertebrates and estuarine-breeding waterbirds .
Most salmon are anadromous , a term which comes from the Greek anadromos , meaning "running upward". [ 4 ] Anadromous fish grow up mostly in the saltwater in oceans. When they have matured they migrate or "run up" freshwater rivers to spawn in what is called the salmon run. [ 5 ]
Anadromous salmon are Northern Hemisphere fish that spend their ocean phase in either the Atlantic Ocean or the Pacific Ocean . They do not thrive in warm water. There is only one species of salmon found in the Atlantic, commonly called the Atlantic salmon . These salmon run up rivers on both sides of the ocean. Seven different species of salmon inhabit the Pacific (see table), and these are collectively referred to as Pacific salmon . Five of these species run up rivers on both sides of the Pacific, but two species are found only on the Asian side. [ 6 ] In the early 19th century, Chinook salmon were successfully established in the Southern Hemisphere, far from their native range, in New Zealand rivers. Attempts to establish anadromous salmon elsewhere have not succeeded. [ 7 ]
The life cycle of an anadromous salmon begins and, if it survives the full course of its natural life, usually ends in a gravel bed in the upper reaches of a stream or river. These are the salmon spawning grounds where salmon eggs are deposited, for safety, in the gravel. The salmon spawning grounds are also the salmon nurseries, providing a more protected environment than the ocean usually offers. After 2 to 6 months the eggs hatch into tiny larvae called sac fry or alevin . The alevin have a sac containing the remainder of the yolk, and they stay hidden in the gravel while they feed on the yolk. When the yolk has gone they must find food for themselves, so they leave the protection of the gravel and start feeding on plankton . At this point the baby salmon are called fry . At the end of the summer the fry develop into juvenile fish called parr . Parr feed on small invertebrates and are camouflaged with a pattern of spots and vertical bars. They remain in this stage for up to three years. [ 16 ] [ 17 ]
As they approach the time when they are ready to migrate out to the sea the parr lose their camouflage bars and undergo a process of physiological changes which allows them to survive the shift from freshwater to saltwater. At this point salmon are called smolt . Smolt spend time in the brackish waters of the river estuary while their body chemistry adjusts their osmoregulation to cope with the higher salt levels they will encounter in the ocean. [ 18 ] Smolt also grow the silvery scales which visually confuse ocean predators. When they have matured sufficiently in late spring, and are about 15 to 20 centimetres long, the smolt swim out of the rivers and into the sea. There they spend their first year as a post-smolt . Post-smolt form schools with other post-smolt, and set off to find deep-sea feeding grounds. They then spend up to four more years as adult ocean salmon while their full swimming ability and reproductive capacity develop. [ 16 ] [ 17 ] [ 18 ]
Then, in one of the animal kingdom's more extreme migrations , the salmon return from the saltwater ocean back to a freshwater river to spawn afresh. [ 19 ]
After several years wandering huge distances in the ocean, most surviving salmon return to the same natal rivers where they were spawned. Then most of them swim up the rivers until they reach the very spawning ground that was their original birthplace. [ 20 ]
There are various theories about how this happens. One theory is that there are geomagnetic and chemical cues which the salmon use to guide them back to their birthplace. The fish may be sensitive to the Earth's magnetic field, which could allow the fish to orient itself in the ocean, so it can navigate back to the estuary of its natal stream. [ 21 ]
Salmon have a strong sense of smell. Speculation about whether odours provide homing cues go back to the 19th century. [ 22 ] In 1951, Hasler hypothesised that, once in vicinity of the estuary or entrance to its birth river, salmon may use chemical cues which they can smell, and which are unique to their natal stream, as a mechanism to home onto the entrance of the stream. [ 23 ] In 1978, Hasler and his students found that the way salmon locate their home rivers with such precision was because they could recognise its characteristic smell. They further demonstrated that the smell of their river becomes imprinted in salmon when they transform into smolts, just before they migrate out to sea. [ 20 ] [ 24 ] [ 25 ] Homecoming salmon can also recognise characteristic smells in tributary streams as they move up the main river. They may also be sensitive to characteristic pheromones given off by juvenile conspecifics . There is evidence that they can "discriminate between two populations of their own species". [ 20 ] [ 26 ]
The recognition that each river and tributary has its own characteristic smell, and the role this plays as a navigation aid, led to a widespread search for a mechanism or mechanisms that might allow salmon to navigate over long distances in the open ocean. In 1977, Leggett identified, as mechanisms worth investigating, the use of the sun for navigation, and orientation to various possible gradients, such as temperature, salinity or chemicals gradients, or geomagnetic or geoelectric fields. [ 27 ] [ 28 ]
There is little evidence salmon use clues from the sun for navigation. Migrating salmon have been observed maintaining direction at nighttime and when it is cloudy. Likewise, electronically tagged salmon were observed to maintain direction even when swimming in water much too deep for sunlight to be of use. [ 29 ]
In 1973, it was shown that Atlantic salmon have conditioned cardiac responses to electric fields with strengths similar to those found in oceans. "This sensitivity might allow a migrating fish to align itself upstream or downstream in an ocean current in the absence of fixed references." [ 30 ] In 1988, researchers found iron, in the form of single domain magnetite , resides in the skulls of sockeye salmon. The quantities present are sufficient for magnetoception . [ 31 ]
Tagging studies have shown a small number of fish do not find their natal rivers, but travel instead up other, usually nearby streams or rivers. [ 32 ] [ 33 ] It is important some salmon stray from their home areas; otherwise new habitats could not be colonized. In 1984, Quinn hypothesized there is a dynamic equilibrium, controlled by genes, between homing and straying. [ 34 ] If the spawning grounds have a uniform high quality, then natural selection should favour the descendants that home accurately. If the spawning grounds have a variable quality, then natural selection should favour a mixture of the descendants that stray and the descendants that home accurately. [ 21 ] [ 34 ]
Prior to the run up the river, the salmon undergo profound physiological changes. Fish swim by contracting longitudinal red muscle and obliquely oriented white muscles. Red muscles are used for sustained activity, such as ocean migrations. White muscles are used for bursts of activity, such as bursts of speed or jumping. [ 35 ] As the salmon comes to end of its ocean migration and enters the estuary of its natal river, its energy metabolism is faced with two major challenges: it must supply energy suitable for swimming the river rapids, and it must supply the sperm and eggs required for the reproductive events ahead. The water in the estuary receives the freshwater discharge from the natal river. Relative to ocean water, this has a high chemical load from surface runoff . Researchers in 2009 found evidence that, as the salmon encounter the resulting drop in salinity and increase in olfactory stimulation, two key metabolic changes are triggered: there is a switch from using red muscles for swimming to using white muscles, and there is an increase in the sperm and egg load. "Pheromones at the spawning grounds [trigger] a second shift to further enhance reproductive loading." [ 36 ]
The salmon also undergo radical morphological changes as they prepare for the spawning event ahead. All salmon lose the silvery blue they had as ocean fish, and their colour darkens, sometimes with a radical change in hue. Salmon are sexually dimorphic , and the male salmon develop canine-like teeth and their jaws develop a pronounced curve or hook ( kype ). Some species of male salmon grow large humps. [ 37 ]
Salmon start the run in peak condition, the culmination of years of development in the ocean. They need high swimming and leaping abilities to battle the rapids and other obstacles the river may present, and they need a full sexual development to ensure a successful spawn at the end of the run. All their energy goes into the physical rigours of the journey and the dramatic morphological transformations they must still complete before they are ready for the spawning events ahead.
The run up the river can be exhausting, sometimes requiring the salmon to battle hundreds of miles upstream against strong currents and rapids. They cease feeding during the run. [ 5 ] Chinook and sockeye salmon from central Idaho must travel 900 miles (1,400 km) and climb nearly 7,000 feet (2,100 m) before they are ready to spawn. Salmon deaths that occur on the upriver journey are referred to as en route mortality . [ 38 ]
Salmon negotiate waterfalls and rapids by leaping or jumping. They have been recorded making vertical jumps as high as 3.65 metres (12 ft). [ 39 ] The height that can be achieved by a salmon depends on the position of the standing wave or hydraulic jump at the base of the fall, as well as how deep the water is. [ 39 ]
Fish ladders , or fishways, are specially designed to help salmon and other fish to bypass dams and other man-made obstructions, and continue on to their spawning grounds further upriver. [ 40 ] Data suggest that navigation locks have a potential to be operated as vertical slot fishways to provide increased access for a range of biota, including poor swimmers. [ 41 ] [ clarification needed ]
Skilled predators, such as bears , bald eagles and fishermen can await the salmon during the run. Normally solitary animals, grizzly bears congregate by streams and rivers when the salmon spawn. [ 3 ] [ 42 ] Predation from harbor seals , California sea lions , and Steller sea lions can pose a significant threat, even in river ecosystems. [ 43 ] [ 44 ]
Black bears also fish the salmon. Black bears usually operate during the day, but when it comes to salmon they tend to fish at night. [ 45 ] This is partly to avoid competition with the more powerful brown bears, but it is also because they catch more salmon at night. [ 46 ] During the day, salmon are very evasive and attuned to visual clues, but at night they focus on their spawning activities, generating acoustic clues the bears tune into. [ 45 ] Black bears may also fish for salmon during the night because their black fur is easily spotted by salmon in the daytime. In 2009, researchers compared the foraging success of black bears with the white-coated Kermode bear , a morphed subspecies of the black bear. They found the Kermode bear had no more success catching salmon at night time, but had greater success than the black bears during the day. [ 47 ]
Otters are also common predators. In 2011, researchers showed that when otters predate salmon, the salmon can "sniff them out". They demonstrated that once otters have eaten salmon, the remaining salmon could detect and avoid the waters where otter faeces was present. [ 48 ] [ 49 ]
The term prespawn mortality is used to refer to fish that arrive successfully at the spawning grounds, and then die without spawning. Prespawn mortality is surprisingly variable, with one study observing rates between 3% and 90%. [ 38 ] [ 50 ] Factors that contribute to these mortalities include high temperatures, [ 51 ] [ 52 ] high river discharge rates, [ 53 ] and parasites and diseases. [ 50 ] [ 54 ] "At present there are no reliable indicators to predict whether an individual arriving at a spawning area will in fact survive to spawn." [ 38 ]
The eggs of a female salmon are called her roe . To lay her roe, the female salmon builds a spawning nest, called a redd , in a riffle with gravel as its streambed . A riffle is a relatively shallow length of stream where the water is turbulent and flows faster. She builds the redd by using her tail ( caudal fin ) to create a low-pressure zone, lifting gravel to be swept downstream, and excavating a shallow depression. The redd may contain up to 5,000 eggs, each about the size of a pea, covering 30 square feet (2.8 m 2 ). [ 55 ] The eggs usually range from orange to red. One or more males will approach the female in her redd, depositing his sperm, or milt, over her eggs. [ 56 ] The female then covers the eggs by disturbing the gravel at the upstream edge of the depression before moving on to make another redd. The female will make as many as seven redds before her supply of eggs is exhausted. [ 56 ] [ 57 ]
Male pink salmon and some sockeye salmon develop pronounced humps just before they spawn. These humps may have evolved because they confer species advantages. The humps make it less likely the salmon will spawn in the shallow water at margins of the streambed, which tend to dry out during low water flows or freeze in winter. Further, riffles can contain many salmon spawning simultaneously, as in the image on the right. Predators, such as bears, will be more likely to catch the more visually prominent humped males, with their humps projecting above the surface of the water. This may provide a protective buffer for the females. [ 58 ]
Dominant male salmon defend their redds by rushing at and chasing intruders. They butt and bite them with the canine-like teeth they developed for the spawning event. The kypes are used to clamp around the base of the tail ( caudal peduncle ) of an opponent. [ 58 ]
The physical condition of the salmon deteriorates the longer they remain in fresh water. Once the salmon have spawned, most of them deteriorate rapidly (a.k.a. "spawned out") and soon die. Some deteriorating salmon are still alive, but their bodies have already begun the process of rotting, [ 59 ] and these deteriorating salmon are sometimes colloquially called "zombie fish". [ 60 ] This is because upstream freshwater bodies (especially creeks) typically do not have sufficient food available for the adult salmon diet, and they have used large amounts of energy swimming upriver, thus exhausting their own internal nutrient reserves. [ 61 ] [ 62 ] Spawning salmon also have programmed senescence , which is "characterized by immunosuppression and organ deterioration", making them more vulnerable to diseases. [ 38 ] [ 63 ] [ 64 ] Most zombie fish die within days of spawning, but some can last up to a couple of weeks. [ 59 ] Once the salmon die in the river, they are either scavenged by other animals, or they decompose and release inorganic nutrients to the plankton in the river and the riparian vegetation in the floodplain . [ 61 ]
The Pacific salmon are a classic example of a semelparous animal, which reproduce only once in their lifetime. Semelparity is sometimes called "big bang" reproduction, since the single reproductive event of semelparous organisms is usually large and fatal to the spawners. [ 65 ] It is an evolutionary strategy that concentrates all available resources into maximizing reproduction, at the expense of individual organism's life, which is common among insects but rare among vertebrates . [ 62 ] All six species of Pacific salmons live for many years in the ocean before swimming to the freshwater stream of its birth, spawning, and then dying. Most Atlantic salmon also die after spawning, but about 5 to 10% (mostly female) return to the ocean where they can recover and spawn again the next season. [ 18 ]
In the Pacific Northwest and Alaska, salmon is a keystone species , supporting wildlife from birds to bears and otters. [ 66 ] The bodies of salmon represent a transfer of nutrients from the ocean, rich in nitrogen, sulfur, carbon and phosphorus, to the forest ecosystem .
Grizzly bears function as ecosystem engineers , capturing salmon and carrying them into adjacent wooded areas. There they deposit nutrient-rich urine and feces and partially eaten carcasses. It has been estimated that bears leave up to half the salmon they harvest on the forest floor, [ 67 ] [ 68 ] in densities that can reach 4,000 kilograms per hectare, [ 69 ] providing as much as 24% of the total nitrogen available to the riparian woodlands. [ 3 ] The foliage of spruce trees up to 500 m (1,600 ft) from a stream where grizzlies fish salmon have been found to contain nitrogen originating from fished salmon. [ 3 ]
Salmon continue to surprise us, showing us new ways in which their oceanic migrations eventually permeate entire terrestrial ecosystems. In terms of providing food and nutrients to a whole food web, we like to think of them as North America's answer to the Serengeti's wildebeest . [ 70 ]
Wolves normally hunt for deer. A 2008 study suggests that when the salmon run starts, wolves choose to fish for salmon, even if plenty of deer are still available. [ 71 ] "Selecting benign prey such as salmon makes sense from a safety point of view. While hunting deer, wolves commonly incur serious and often fatal injuries. In addition to safety benefits we determined that salmon also provides enhanced nutrition in terms of fat and energy." [ 70 ]
The upper reaches of the Chilkat River in Alaska has particularly good spawning grounds. Each year these attract a run of up to half a million chum salmon . As the salmon run up the river, bald eagles arrive in their thousands to feast at the spawning grounds. This results in some of the world's largest congregations of bald eagles. The number of participating eagles is directly correlated with the number of spawning salmon. [ 72 ]
Residual nutrients from salmon can also accumulate downstream in estuaries. A 2010 study suggests the density and diversity of many estuarine breeding birds in the summer "were strongly predicted by salmon biomass in the autumn". [ 73 ] Anadromous salmon provide nutrients to these "diverse assemblages ... ecologically comparable to the migrating herds of wildebeest in the Serengeti ". [ 69 ]
In 1997, researchers noted that the future of salmon runs worldwide would depend on many factors, most of which are driven by human actions. Among the key driving factors are (1) harvest of salmon by commercial, recreational, and subsistence fishing, (2) alterations in stream and river channels, including construction of dikes and other riparian corridor modifications, (3) electricity generation, flood control, and irrigation supplied by dams, (4) alteration by humans of freshwater, estuarine , and marine environments used by salmon, coupled with aquatic changes due to climate and ocean circulatory regimes, (5) water withdrawals from rivers and reservoirs for agricultural, municipal, or commercial purposes, (6) changes in climate caused at least in part by human activities, (7) competition from non-native fishes, (8) salmon predation by marine mammals, birds, and other fish species, (9) diseases and parasites, including those from outside the native region, and (10) reduced nutrient replenishment from decomposing salmon. [ 74 ]
In 2009, NOAA advised that continued runoff into North American rivers of three widely used pesticides containing neurotoxins would "jeopardize the continued existence" of endangered and threatened Pacific salmon. [ 75 ] [ 76 ] Global warming could see the end of some salmon runs by the end of the century, [ according to whom? ] such as the Californian runs of Chinook salmon. [ 77 ] [ 78 ] A 2010 United Nations report said that increases in acidification of oceans would mean that shellfish such as Pteropods , an important component of the ocean salmon diet, would be finding it more difficult to build their aragonite shells. [ 79 ] There were concerns [ by whom? ] that this too could endanger future salmon runs. [ 80 ]
In a 1982 video game called Salmon Run , the player takes the role of Sam the Salmon, swimming upriver to mate. Along the way he encounters waterfalls, a bear, fishermen, and seagulls.
In the 2003 Disney animated feature film, Brother Bear , Kenai and Koda reached the salmon run and met a large group of bears led by Tug at the Annual Salmon Run. Featuring the song " Welcome " by The Blind Boys of Alabama and Phil Collins . [ citation needed ]
Splatoon 2 and 3 introduce the game mode " Salmon Run " where players fight off fictional Salmonids , a race of salmon-like beings. Grizzo Industries, owned by Mr. Grizz , employs players to hunt for salmonids and their eggs, similar to Grizzly bears hunting salmon in nature. The game's lore suggests that the Salmonids participate in a massive salmon migration every 70 years, which coincides with the time the Splatoon series takes place. | https://en.wikipedia.org/wiki/Salmon_run |
Phenyl salicylate , or salol , is the organic compound with the formula C 6 H 5 O 2 C 6 H 4 OH. It is a white solid. It is occasionally used in sunscreens and as an antiseptic. [ 3 ]
The title compound was synthesized first in 1883 by the Polish chemist and doctor Marceli Nencki (who didn't publish his findings) and then independently in 1885 by the German chemist Richard Seifert ( de ) (1861–1919) (who did publish his findings). It is synthesized by heating salicylic acid with phenol in the presence of phosphoryl chloride . [ 4 ] It also arises from heating salicylic acid: [ 5 ]
The conversion entails dehydration and decarboxylation. Heating phenyl salicylate in turn gives xanthone . [ 6 ] [ 3 ]
In this conversion, phenol is produced as well as carbon dioxide.
In the salol reaction , phenyl salicylate reacts with o -toluidine in 1,2,4-trichlorobenzene at elevated temperatures to the corresponding amide o -salicylotoluide. [ 7 ] Salicylamides are a type of drug.
It has been used as an antiseptic [ 8 ] based on the antibacterial activity upon hydrolysis in the small intestine. [ 9 ]
It acts as a mild analgesic . [ 10 ]
The Swiss physician Hermann Sahli (sometimes spelled "Saly") (1856–1933) sought a substitute for sodium salicylate, which was used as a treatment for rheumatoid arthritis but which wasn't tolerated by some patients. So Dr. Sahli asked the Polish chemist and doctor Marceli Nencki of Bern , Switzerland, if he knew of a salicylate compound that lacked sodium salicylate's side effects. [ 11 ] Nencki recommended phenyl salicylate, which he had synthesized circa 1883. [ 12 ] [ 13 ] While Nencki had been investigating how phenyl salicylate behaved in the body, he hadn't published his findings. [ 14 ] Meanwhile, the German chemist Richard Seifert ( de ) (1861–1919), a student of the German chemist Rudolf Wilhelm Schmitt ( de ) (1830–1898), [ 15 ] independently synthesized phenyl salicylate in 1885. [ 16 ] In 1885, Seifert accepted a position at the Heyden chemical corporation ( de ) of Radebeul , Germany, which manufactured salicylic acid. [ 17 ] The United States granted to Nencki and Seifert a patent for the production of phenyl salicylate, [ 18 ] whereas Germany granted a patent for its production to Nencki and the Heyden corporation. [ 19 ] The Heyden company subsequently sold phenyl salicylate as a pharmaceutical, under the commercial name "Salol", [ 20 ] a contraction of "SALicylate of phenOL". [ 21 ] Among other applications, [ 22 ] Salol was used as an orally administered antiseptic for the small intestine, where the compound is hydrolyzed into salicylic acid and phenol. [ 18 ]
Phenyl salicylate is used in school laboratory demonstrations on how cooling rates affect crystal size in igneous rocks , and can be used to demonstrate seed crystal selectiveness. [ citation needed ] | https://en.wikipedia.org/wiki/Salol_reaction |
In anatomical contexts, salpinx is used to refer to a type of tube. Per Terminologia Anatomica , the Latin term "tuba" is usually used to describe most tubes (after the Roman tuba , not the modern tuba ), but the term "salpinges" and its adjectival derivatives are still sometimes used to describe the following two "tubes": [ 1 ] | https://en.wikipedia.org/wiki/Salpinx_in_anatomy |
A salsabil (or salasabil [ 1 ] ), also known as a shadirwan , [ 2 ] is a type of fountain which maximizes the surface area of the water. It is used for evaporative cooling of buildings, cooling and aeration of drinking water, and ornament [ 3 ] [ 4 ] (it has also been used to prevent eavesdropping [ 5 ] ). The water may flow in a thin sheet or thin streams, often over a wavy surface with many little waterfalls. [ 4 ] [ 3 ] Its use extends from southern Spain through north Africa and the Middle East to northern India . [ 3 ]
The name salsabil ( Arabic : سلسبيل ) likely derives from a Qur'anic reference . [ 6 ] The term shadirwan is also used for devices for aerating drinking water. [ 7 ] [ 2 ] However, the term shadirwan or shadirvan ( Arabic : شاذروان , Persian : شادروان , Turkish : şadırvan ) has slightly different uses in other cultures, such as designating a central ablutions fountain for a mosque courtyard in Turkish (see shadirvan ). [ 8 ] [ 9 ] : 459
The water flows in a manner designed to maximize the surface area, and thus evaporation. A salsabil may be a near-vertical marble waterfall mounted on a wall, [ 4 ] or the sheet of water may flow down a slanted chute. [ 3 ]
Evaporative cooling causes the water and the surrounding air to cool as some of the water evaporates. Passive ventilation may be used to maximize the flow of unsaturated air over the water surface and carry the cooled air to where it is needed in the building. Salasabils are often used with windcatchers . [ 10 ]
A salsabil may also be used to aerate water for drinking in a sabil (or sebil; Arabic : سبيل , Turkish : sebil ). [ 11 ] : 63, 262 Salsabils, in the form of inclined marble slabs over which drinking water flowed before being dispensed, were often included inside the sabils of Mamluk architecture. [ 7 ] [ 11 ] : 63, 262
Salasabils were used in Mughal architecture from the 1200s to the 1600s. They were also used in recent centuries in Iran . [ 3 ] They were sometimes used as decorative features in Ottoman domestic architecture. [ 12 ] [ 9 ] : 441 | https://en.wikipedia.org/wiki/Salsabil_(fountain) |
In pathology , salt-and-pepper chromatin , also salt-and-pepper nuclei and stippled chromatin , refers to cell nuclei that demonstrate granular chromatin (on light microscopy ). [ 1 ]
Salt-and-pepper chromatin is typically seen in endocrine tumours such as medullary thyroid carcinoma , neuroendocrine tumours [ 2 ] and pheochromocytoma . [ 3 ]
This article related to pathology is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Salt-and-pepper_chromatin |
Salt-concrete (or salzbeton ) is a building material that is used to reduce the water inflow in mining shafts in salt mines. It is composed of 16% cement , 39% halite , 16% limestone powder, 14% water and 15% sand. [ 1 ]
Salt-concrete was used for the first time in 1984 in the potash mine in Rocanville in Canada . [ 2 ] A salt-concrete seal was also installed in the Asse II mine in Lower Saxony in 1995. [ 3 ]
Since the end of the repository for radioactive waste Morsleben in 1998, the salt dome stability deteriorated to a state where it could collapse. Since 2003, a volume of 480,000 m 3 of salt-concrete has been pumped into the pit to temporarily stabilize the upper levels. In addition another 4,000,000 m 3 of salt-concrete will be used to temporarily stabilize the lower levels. [ 4 ] | https://en.wikipedia.org/wiki/Salt-concrete |
Salt-effect distillation is a method of extractive distillation in which a salt is dissolved in the mixture of liquids to be distilled. The salt acts as a separating agent by raising the relative volatility of the mixture and by breaking any azeotropes that may otherwise form. The technique is first attested in writings on alcohol attributed to Jabir ibn Hayyan (9th c. CE).
The salt is fed into the distillation column at a steady rate by adding it to the reflux stream at the top of the column. It dissolves in the liquid phase, and since it is non- volatile , flows out with the heavier bottoms stream. The bottoms are partially or completely evaporated to recover the salt for reuse.
Extractive distillation is more costly than ordinary fractional distillation due to costs associated with the recovery of the separating agent. One advantage of salt-effect distillation over other types of azeotropic distillation is the potential for reduced costs associated with energy usage. In addition, the salt ions have a greater effect on the volatility of the mixture to be distilled than other liquid-separating agents. [ 1 ] Commercial usage of salt-effect distillation includes adding magnesium nitrate to an aqueous solution of nitric acid to concentrate it further. Calcium chloride is added to acetone - methanol and water - isopropanol mixtures in order to facilitate separation. [ 2 ] | https://en.wikipedia.org/wiki/Salt-effect_distillation |
In chemistry , salt-free reduction describes methodology for reduction of metal halides by electron-rich trimethylsilyl reagents. Traditional reductions of metal halides are accomplished with alkali metals, a process that cogenerates alkali metal salts. Using the salt-free reduction, the reduction of metal halides is accompanied by formation of neutral organic compounds that can be easily removed from the inorganic or organometallic product. In addition to the reduction of metal halides, the reagents associated with this methodology are applicable to deoxygenation of organic substrates. [ 1 ]
A typical reducing agent is N,N'-bis(trimethylsilyl)-4,4'-bipyridinylidene. Related pyrazine - and cyclohexadiene -based reagents have been developed. They are red or orange THF-soluble solids. The bipyridine reagent is produced by reduction of 4,4'-bipyridine in the presence of trimethylsilyl chloride (Me = CH 3 ): [ 2 ]
A typical reduction reaction is the conversion of tungsten hexachloride to the tetrachloride using the silylated pyrazine reagent: | https://en.wikipedia.org/wiki/Salt-free_reduction |
SaltMod is computer program for the prediction of the salinity of soil moisture , groundwater and drainage water, the depth of the watertable , and the drain discharge (hydrology) in irrigated agricultural lands, using different (geo)hydrologic conditions, varying water management options, including the use of ground water for irrigation, and several cropping rotation schedules.
The water management options include irrigation, drainage, and the use of subsurface drainage water from pipe drains, ditches or wells for irrigation.
The majority of the computer models available for water and solute transport in the soil (e.g. Swatre, [ 1 ] DrainMod [ 2 ] ) are based on Richard's differential equation for the movement of water in unsaturated soil in combination with a differential salinity dispersion equation . The models require input of soil characteristics like the relation between unsaturated soil moisture content, water tension, hydraulic conductivity and dispersivity.
These relations vary to a great extent from place to place and are not easy to measure. The models use short time steps and need at least a daily data base of hydrological phenomena. Altogether this makes model application to a fairly large project the job of a team of specialists with ample facilities.
Literature references (chronological) to case studies after 2000: [ 3 ] [ 4 ] [ 5 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ] [ 10 ] [ 11 ] [ 12 ] [ 13 ] [ 14 ] [ 15 ] [ 16 ] [ 17 ] [ 18 ] [ 19 ] [ 20 ] [ 21 ]
Older examples of application can be found in:
There is a need for a computer program that is easier to operate and that requires a simpler data structure than most currently available models. Therefore, the SaltModod program was designed keeping in mind a relative simplicity of operation to facilitate the use by field technicians, engineers and project planners instead of specialized geo-hydrologists .
It aims at using input data that are generally available, or that can be estimated with reasonable accuracy, or that can be measured with relative ease. Although the calculations are done numerically and have to be repeated many times, the final results can be checked by hand using the formulas in the manual.
SaltMod's objective is to predict the long-term hydro-salinity in terms of general trends , not to arrive at exact predictions of how, for example, the situation would be on the first of April in ten years from now.
Further, SaltMod gives the option of the re-use of drainage and well water (e.g. for irrigation) and it can account for farmers' response to waterlogging , soil salinity , water scarcity and over-pumping from the aquifer . Also it offers the possibility to introduce subsurface drainage systems at varying depths and with varying capacity so that they can be optimized .
Other features of Saltmod are found in the next section.
The computation method Saltmod is based on seasonal water balances of agricultural lands. Four seasons in one year can be distinguished, e.g. dry, wet, cold, hot, irrigation or fallow seasons. The number of seasons (Ns) can be chosen between a minimum of one and a maximum of four. The larger the number of seasons becomes, the larger is the number of input data required. The duration of each season (Ts) is given in number of months (0 < Ts < 12). Day to day water balances are not considered for several reasons:
The method uses seasonal water balance components as input data. These are related to the surface hydrology (like rainfall , evaporation , irrigation, use of drain and well water for irrigation, runoff ), and the aquifer hydrology (like upward seepage, natural drainage, pumping from wells). The other water balance components (like downward percolation , upward capillary rise , subsurface drainage ) are given as output. The quantity of drainage water, as an output, is determined by two drainage intensity factors for drainage above and below drain level respectively (to be given with the input data), a drainage reduction factor (to simulate a limited operation of the drainage system), and the height of the water table, resulting from the computed water balance. Variation of the drainage intensity factors and the drainage reduction factor gives the opportunity to simulate the effect of different drainage options.
The input data on irrigation , evaporation , and surface runoff are to be specified per season for three kinds of agricultural practices, which can be chosen at the discretion of the user:
The groups, expressed in fractions of the total area, may consist of combinations of crops or just of a single kind of crop. For example, as the A type crops one may specify the lightly irrigated cultures, and as the B type the more heavily irrigated ones, such as sugarcane and rice . But one can also take A as rice and B as sugarcane, or perhaps trees and orchards . The A, B and/or U crops can be taken differently in different seasons , e.g. A= wheat + barley in winter and A= maize in summer while B= vegetables in winter and B= cotton in summer. Un-irrigated land can be specified in two ways: (1) as U=1−A−B and (2) as A and/or B with zero irrigation. A combination can also be made. Further, a specification must be given of the seasonal rotation of the different land uses over the total area, e.g. full rotation, no rotation at all, or incomplete rotation. This occurs with a rotation index. The rotations are taken over the seasons within the year. To obtain rotations over the years it is advisable to introduce annual input changes. When a fraction A1, B1 and/or U1 in the first season differs from fractions are A2, B2 and/or U2 in the second season, because the irrigation regimes in the seasons differ, the program will detect that a certain rotation occurs. If one wishes to avoid this, one may specify the same fractions in all seasons (A2=A1, B2=B1, U2=U1), but the crops and irrigation quantities may have to be adjusted in proportion. Cropping rotation schedules vary widely in different parts of the world. Creative combinations of area fractions, rotation indexes, irrigation quantities and annual input changes can accommodate many types of agricultural practices.
Variation of the area fractions and/or the rotational schedule gives the opportunity to simulate the effect of different agricultural practices on the water and salt balance.
Saltmod accepts four different reservoirs, three of which are in the soil profile:
The upper soil reservoir is defined by the soil depth from which water can evaporate or be taken up by plant roots. It can be equal to the rootzone. The root zone can be saturated, unsaturated , or partly saturated, depending on the water balance . All water movements in this zone are vertical, either upward or downward, depending on the water balance. (In a future version of Saltmod, the upper soil reservoir may be divided into two equal parts to detect the trend in the vertical salinity distribution.) The transition zone can also be saturated, unsaturated or partly saturated. All flows in this zone are vertical, except the flow to subsurface drains. If a horizontal subsurface drainage system is present, this must be placed in the transition zone, which is then divided into two parts: an upper transition zone (above drain level) and a lower transition zone (below drain level). If one wishes to distinguish an upper and lower part of the transition zone in the absence of a subsurface drainage system, one may specify in the input data a drainage system with zero intensity. The aquifer has mainly horizontal flow. Pumped wells, if present, receive their water from the aquifer only.
The water balances are calculated for each reservoir separately as shown in the article Hydrology (agriculture) . The excess water leaving one reservoir is converted into incoming water for the next reservoir. The three soil reservoirs can be assigned a different thickness and storage coefficients, to be given as input data. In a particular situation, the transition zone or the aquifer need not be present. Then, it must be given a minimum thickness of 0.1 m. The depth of the water table , calculated from the water balances, is assumed to be the same for the whole area. If this assumption is not acceptable, the area must be divided into separate units. Under certain conditions, the height of the water table influences the water balance components. For example, a rise of the water table towards the soil surface may lead to an increase of evaporation , surface runoff , and subsurface drainage, or a decrease of percolation losses from canals. This, in turn, leads to a change of the water balance, which again influences the height of the water table, etc. This chain of reactions is one of the reasons why Saltmod has been developed into a computer program. It takes a number of repeated calculations ( iterations ) to find the correct equilibrium of the water balance, which would be a tedious job if done by hand. Other reasons are that a computer program facilitates the computations for different water management options over long periods of time (with the aim to simulate their long-term effects) and for trial runs with varying parameters.
The sub-surface drainage can be accomplished through drains or pumped wells . The subsurface drains are characterized by drain depth and drainage capacity factor . The drains are located in the transition zone. The subsurface drainage facility can be applied to natural or artificial drainage systems. The functioning of an artificial drainage system can be regulated through a drainage control factor . When no drainage system is present, installing drains with zero capacity offers the opportunity to obtain separate water and salt balances for an upper and lower part of the transition zone. The pumped wells are located in the aquifer. Their functioning is characterized by the well discharge. The drain and well water can be used for irrigation through a re-use factor . This may affect the salt balance and the irrigation efficiency or sufficiency.
The salt balances are calculated for each reservoir separately. They are based on their water balances , using the salt concentrations of the incoming and outgoing water. Some concentrations must be given as input data, like the initial salt concentrations of the water in the different soil reservoirs, of the irrigation water and of the incoming ground water in the aquifer.
The concentrations are expressed in terms of electric conductivity (EC in dS/m). When the concentrations are known in terms of g salt/L water, the rule of thumb: 1 g/L -> 1.7 dS/m can be used. Usually, salt concentrations of the soil are expressed in ECe, the electric conductivity of an extract of a saturated soil paste (saturation extract). In Saltmod, the salt concentration is expressed as the EC of the soil moisture when saturated under field conditions. As a rule, one can use the conversion rate EC : ECe = 2 : 1. Salt concentrations of outgoing water (either from one reservoir into the other or by subsurface drainage) are computed on the basis of salt balances, using different leaching or salt mixing efficiencies to be given with the input data. The effects of different leaching efficiencies can be simulated by varying their input value.
If drain or well water is used for irrigation, the method computes the salt concentration of the mixed irrigation water in the course of the time and the subsequent effect on the soil and ground water salinities, which again influences the salt concentration of the drain and well water. By varying the fraction of used drain or well water (to be given in the input data), the long-term effect of different fractions can be simulated.
The dissolution of solid soil minerals or the chemical precipitation of poorly soluble salts is not included in the computation method, but to some extent it can be accounted for through the input data, e.g. by increasing or decreasing the salt concentration of the irrigation water or of the incoming water in the aquifer.
If required, farmers' responses to water logging and soil salinity can be automatically accounted for. The method can gradually decrease:
Response (1) is different for ponded (submerged) rice (paddy) and "dry foot" crops.
The responses influence the water and salt balances, which, in their turn, slow down the process of water logging and salinization. Ultimately an equilibrium situation will be brought about.
The user can also introduce farmers' responses by manually changing the relevant input data. Perhaps it will be useful first to study the automatic farmers' responses and their effect and thereafter decide what the farmers' responses will be in the view of the user.
The responses influence the water and salt balances , which, in their turn, slow down the process of water logging and salinization. Ultimately an equilibrium situation will be brought about.
The user can also introduce farmers' responses by manually changing the relevant input data. Perhaps it will be useful first to study the automatic farmers' responses and their effect and thereafter decide what the farmers' responses will be in the view of the user.
The program may run with fixed input data for the number of years determined by the user. This option can be used to predict future developments based on long-term average input values, e.g. rainfall, as it will be difficult to assess the future values of the input data year by year.
The program also offers the possibility to follow historic records with annually changing input values (e.g. rainfall, irrigation, agricultural practices), the calculations must be made year by year. If this possibility is chosen, the program creates transfer files by which the final conditions of the previous year (e.g. water table and salinity) are automatically used as the initial conditions for the subsequent period. This facility makes it possible to use various generated rainfall sequences drawn randomly from a known rainfall probability distribution and obtain a stochastic prediction of the resulting output parameters.
If the computations are made with annual changes, not all input parameters can be changed, notably the thickness of the soil reservoirs and their total porosities as these would cause illogical shifts in the water and salt balances.
The output of Saltmod is given for each season of any year during any number of years, as specified with the input data. The output data comprise hydrological and salinity aspects.
The data are filed in the form of tables that can be inspected directly or further analyzed with spreadsheet programs.
As the soil salinity is very variable from place to place (figure left) SaltMod includes frequency distributions in the output. The figure was made with the CumFreq program [13] .
The program offers the possibility to develop a multitude of relations between varied input data, resulting outputs and time. However, as it is not possible to foresee all different uses that may be made, the program offers only a limited number of standard graphics .
The program is designed to make use of spreadsheet programs for the detailed output analysis, in which the relations between various input and output variables can be established according to the scenario developed by the user.
Although the computations need many iterations , all the end results can be checked by hand using the equations presented in the manual. | https://en.wikipedia.org/wiki/SaltMod |
In chemistry , a salt or ionic compound is a chemical compound consisting of an assembly of positively charged ions ( cations ) and negatively charged ions ( anions ), [ 1 ] which results in a compound with no net electric charge (electrically neutral). The constituent ions are held together by electrostatic forces termed ionic bonds .
The component ions in a salt can be either inorganic , such as chloride (Cl − ), or organic , such as acetate ( CH 3 COO − ). Each ion can be either monatomic (termed simple ion ), such as sodium (Na + ) and chloride (Cl − ) in sodium chloride , or polyatomic , such as ammonium ( NH + 4 ) and carbonate ( CO 2− 3 ) ions in ammonium carbonate . Salts containing basic ions hydroxide (OH − ) or oxide (O 2− ) are classified as bases , such as sodium hydroxide and potassium oxide .
Individual ions within a salt usually have multiple near neighbours, so they are not considered to be part of molecules, but instead part of a continuous three-dimensional network. Salts usually form crystalline structures when solid.
Salts composed of small ions typically have high melting and boiling points , and are hard and brittle . As solids they are almost always electrically insulating , but when melted or dissolved they become highly conductive , because the ions become mobile. Some salts have large cations, large anions, or both. In terms of their properties, such species often are more similar to organic compounds.
In 1913 the structure of sodium chloride was determined by William Henry Bragg and his son William Lawrence Bragg . [ 2 ] [ 3 ] [ 4 ] This revealed that there were six equidistant nearest-neighbours for each atom, demonstrating that the constituents were not arranged in molecules or finite aggregates, but instead as a network with long-range crystalline order. [ 4 ] Many other inorganic compounds were also found to have similar structural features. [ 4 ] These compounds were soon described as being constituted of ions rather than neutral atoms , but proof of this hypothesis was not found until the mid-1920s, when X-ray reflection experiments (which detect the density of electrons), were performed. [ 4 ] [ 5 ]
Principal contributors to the development of a theoretical treatment of ionic crystal structures were Max Born , Fritz Haber , Alfred Landé , Erwin Madelung , Paul Peter Ewald , and Kazimierz Fajans . [ 6 ] Born predicted crystal energies based on the assumption of ionic constituents, which showed good correspondence to thermochemical measurements, further supporting the assumption. [ 4 ]
Many metals such as the alkali metals react directly with the electronegative halogens gases to form salts. [ 7 ] [ 8 ]
Salts form upon evaporation of their solutions . [ 9 ] Once the solution is supersaturated and the solid compound nucleates. [ 9 ] This process occurs widely in nature and is the means of formation of the evaporite minerals. [ 10 ]
Insoluble salts can be precipitated by mixing two solutions, one with the cation and one with the anion in it. Because all solutions are electrically neutral, the two solutions mixed must also contain counterions of the opposite charges. To ensure that these do not contaminate the precipitated salt, it is important to ensure they do not also precipitate. [ 11 ] If the two solutions have hydrogen ions and hydroxide ions as the counterions, they will react with one another in what is called an acid–base reaction or a neutralization reaction to form water. [ 12 ] Alternately the counterions can be chosen to ensure that even when combined into a single solution they will remain soluble as spectator ions . [ 11 ]
If the solvent is water in either the evaporation or precipitation method of formation, in many cases the ionic crystal formed also includes water of crystallization , so the product is known as a hydrate , and can have very different chemical properties compared to the anhydrous material. [ 13 ]
Molten salts will solidify on cooling to below their freezing point . [ 14 ] This is sometimes used for the solid-state synthesis of complex salts from solid reactants, which are first melted together. [ 15 ] In other cases, the solid reactants do not need to be melted, but instead can react through a solid-state reaction route . In this method, the reactants are repeatedly finely ground into a paste and then heated to a temperature where the ions in neighboring reactants can diffuse together during the time the reactant mixture remains in the oven. [ 8 ] Other synthetic routes use a solid precursor with the correct stoichiometric ratio of non-volatile ions, which is heated to drive off other species. [ 8 ]
In some reactions between highly reactive metals (usually from Group 1 or Group 2 ) and highly electronegative halogen gases, or water, the atoms can be ionized by electron transfer , [ 16 ] a process thermodynamically understood using the Born–Haber cycle . [ 17 ]
Salts are formed by salt-forming reactions
Ions in salts are primarily held together by the electrostatic forces between the charge distribution of these bodies, and in particular, the ionic bond resulting from the long-ranged Coulomb attraction between the net negative charge of the anions and net positive charge of the cations. [ 18 ] There is also a small additional attractive force from van der Waals interactions which contributes only around 1–2% of the cohesive energy for small ions. [ 19 ] When a pair of ions comes close enough for their outer electron shells (most simple ions have closed shells ) to overlap, a short-ranged repulsive force occurs, [ 20 ] due to the Pauli exclusion principle . [ 21 ] The balance between these forces leads to a potential energy well with minimum energy when the nuclei are separated by a specific equilibrium distance. [ 20 ]
If the electronic structure of the two interacting bodies is affected by the presence of one another, covalent interactions (non-ionic) also contribute to the overall energy of the compound formed. [ 22 ] Salts are rarely purely ionic, i.e. held together only by electrostatic forces. The bonds between even the most electronegative / electropositive pairs such as those in caesium fluoride exhibit a small degree of covalency . [ 23 ] [ 24 ] Conversely, covalent bonds between unlike atoms often exhibit some charge separation and can be considered to have a partial ionic character. [ 22 ] The circumstances under which a compound will have ionic or covalent character can typically be understood using Fajans' rules , which use only charges and the sizes of each ion. According to these rules, compounds with the most ionic character will have large positive ions with a low charge, bonded to a small negative ion with a high charge. [ 25 ] More generally HSAB theory can be applied, whereby the compounds with the most ionic character are those consisting of hard acids and hard bases: small, highly charged ions with a high difference in electronegativities between the anion and cation. [ 26 ] [ 27 ] This difference in electronegativities means that the charge separation, and resulting dipole moment, is maintained even when the ions are in contact (the excess electrons on the anions are not transferred or polarized to neutralize the cations). [ 28 ]
Although chemists classify idealized bond types as being ionic or covalent, the existence of additional types such as hydrogen bonds and metallic bonds , for example, has led some philosophers of science to suggest that alternative approaches to understanding bonding are required. This could be by applying quantum mechanics to calculate binding energies. [ 29 ] [ 30 ]
The lattice energy is the summation of the interaction of all sites with all other sites. For unpolarizable spherical ions, only the charges and distances are required to determine the electrostatic interaction energy. For any particular ideal crystal structure, all distances are geometrically related to the smallest internuclear distance. So for each possible crystal structure, the total electrostatic energy can be related to the electrostatic energy of unit charges at the nearest neighboring distance by a multiplicative constant called the Madelung constant [ 20 ] that can be efficiently computed using an Ewald sum . [ 31 ] When a reasonable form is assumed for the additional repulsive energy, the total lattice energy can be modelled using the Born–Landé equation , [ 32 ] the Born–Mayer equation , or in the absence of structural information, the Kapustinskii equation . [ 33 ]
Using an even simpler approximation of the ions as impenetrable hard spheres, the arrangement of anions in these systems are often related to close-packed arrangements of spheres, with the cations occupying tetrahedral or octahedral interstices . [ 34 ] [ 35 ] Depending on the stoichiometry of the salt, and the coordination (principally determined by the radius ratio ) of cations and anions, a variety of structures are commonly observed, [ 36 ] and theoretically rationalized by Pauling's rules . [ 37 ]
In some cases, the anions take on a simple cubic packing and the resulting common structures observed are:
Some ionic liquids , particularly with mixtures of anions or cations, can be cooled rapidly enough that there is not enough time for crystal nucleation to occur, so an ionic glass is formed (with no long-range order). [ 53 ]
Within any crystal, there will usually be some defects. To maintain electroneutrality of the crystals, defects that involve loss of a cation will be associated with loss of an anion, i.e. these defects come in pairs. [ 54 ] Frenkel defects consist of a cation vacancy paired with a cation interstitial and can be generated anywhere in the bulk of the crystal, [ 54 ] occurring most commonly in compounds with a low coordination number and cations that are much smaller than the anions. [ 55 ] Schottky defects consist of one vacancy of each type, and are generated at the surfaces of a crystal, [ 54 ] occurring most commonly in compounds with a high coordination number and when the anions and cations are of similar size. [ 55 ] If the cations have multiple possible oxidation states , then it is possible for cation vacancies to compensate for electron deficiencies on cation sites with higher oxidation numbers, resulting in a non-stoichiometric compound . [ 54 ] Another non-stoichiometric possibility is the formation of an F-center , a free electron occupying an anion vacancy. [ 56 ] When the compound has three or more ionic components, even more defect types are possible. [ 54 ] All of these point defects can be generated via thermal vibrations and have an equilibrium concentration. Because they are energetically costly but entropically beneficial, they occur in greater concentration at higher temperatures. Once generated, these pairs of defects can diffuse mostly independently of one another, by hopping between lattice sites. This defect mobility is the source of most transport phenomena within an ionic crystal, including diffusion and solid state ionic conductivity . [ 54 ] When vacancies collide with interstitials (Frenkel), they can recombine and annihilate one another. Similarly, vacancies are removed when they reach the surface of the crystal (Schottky). Defects in the crystal structure generally expand the lattice parameters , reducing the overall density of the crystal. [ 54 ] Defects also result in ions in distinctly different local environments, which causes them to experience a different crystal-field symmetry , especially in the case of different cations exchanging lattice sites. [ 54 ] This results in a different splitting of d-electron orbitals , so that the optical absorption (and hence colour) can change with defect concentration. [ 54 ]
Ionic compounds containing hydrogen ions (H + ) are classified as acids , and those containing electropositive cations [ 57 ] and basic anions ions hydroxide (OH − ) or oxide (O 2− ) are classified as bases . Other ionic compounds are known as salts and can be formed by acid–base reactions . [ 58 ] Salts that produce hydroxide ions when dissolved in water are called alkali salts , and salts that produce hydrogen ions when dissolved in water are called acid salts . If the compound is the result of a reaction between a strong acid and a weak base , the result is an acid salt . If it is the result of a reaction between a strong base and a weak acid , the result is a base salt . If it is the result of a reaction between a strong acid and a strong base, the result is a neutral salt. Weak acids reacted with weak bases can produce ionic compounds with both the conjugate base ion and conjugate acid ion, such as ammonium acetate .
Some ions are classed as amphoteric , being able to react with either an acid or a base. [ 59 ] This is also true of some compounds with ionic character, typically oxides or hydroxides of less-electropositive metals (so the compound also has significant covalent character), such as zinc oxide , aluminium hydroxide , aluminium oxide and lead(II) oxide . [ 60 ]
Electrostatic forces between particles are strongest when the charges are high, and the distance between the nuclei of the ions is small. In such cases, the compounds generally have very high melting and boiling points and a low vapour pressure . [ 61 ] Trends in melting points can be even better explained when the structure and ionic size ratio is taken into account. [ 62 ] Above their melting point, salts melt and become molten salts (although some salts such as aluminium chloride and iron(III) chloride show molecule-like structures in the liquid phase). [ 63 ] Inorganic compounds with simple ions typically have small ions, and thus have high melting points, so are solids at room temperature. Some substances with larger ions, however, have a melting point below or near room temperature (often defined as up to 100 °C), and are termed ionic liquids . [ 64 ] Ions in ionic liquids often have uneven charge distributions, or bulky substituents like hydrocarbon chains, which also play a role in determining the strength of the interactions and propensity to melt. [ 65 ]
Even when the local structure and bonding of an ionic solid is disrupted sufficiently to melt it, there are still strong long-range electrostatic forces of attraction holding the liquid together and preventing ions boiling to form a gas phase. [ 66 ] This means that even room temperature ionic liquids have low vapour pressures, and require substantially higher temperatures to boil. [ 66 ] Boiling points exhibit similar trends to melting points in terms of the size of ions and strength of other interactions. [ 66 ] When vapourized, the ions are still not freed of one another. For example, in the vapour phase sodium chloride exists as diatomic "molecules". [ 67 ]
Most salts are very brittle . Once they reach the limit of their strength, they cannot deform malleably , because the strict alignment of positive and negative ions must be maintained. Instead the material undergoes fracture via cleavage . [ 68 ] As the temperature is elevated (usually close to the melting point) a ductile–brittle transition occurs, and plastic flow becomes possible by the motion of dislocations . [ 68 ] [ 69 ]
The compressibility of a salt is strongly determined by its structure, and in particular the coordination number . For example, halides with the caesium chloride structure (coordination number 8) are less compressible than those with the sodium chloride structure (coordination number 6), and less again than those with a coordination number of 4. [ 70 ]
When simple salts dissolve , they dissociate into individual ions, which are solvated and dispersed throughout the resulting solution. Salts do not exist in solution. [ 71 ] In contrast, molecular compounds, which includes most organic compounds, remain intact in solution.
The solubility of salts is highest in polar solvents (such as water ) or ionic liquids , but tends to be low in nonpolar solvents (such as petrol / gasoline ). [ 72 ] This contrast is principally because the resulting ion–dipole interactions are significantly stronger than ion-induced dipole interactions, so the heat of solution is higher. When the oppositely charged ions in the solid ionic lattice are surrounded by the opposite pole of a polar molecule, the solid ions are pulled out of the lattice and into the liquid. If the solvation energy exceeds the lattice energy , the negative net enthalpy change of solution provides a thermodynamic drive to remove ions from their positions in the crystal and dissolve in the liquid. In addition, the entropy change of solution is usually positive for most solid solutes like salts, which means that their solubility increases when the temperature increases. [ 73 ] There are some unusual salts such as cerium(III) sulfate , where this entropy change is negative, due to extra order induced in the water upon solution, and the solubility decreases with temperature. [ 73 ]
The lattice energy , the cohesive forces between these ions within a solid, determines the solubility. The solubility is dependent on how well each ion interacts with the solvent, so certain patterns become apparent. For example, salts of sodium , potassium and ammonium are usually soluble in water. Notable exceptions include ammonium hexachloroplatinate and potassium cobaltinitrite . Most nitrates and many sulfates are water-soluble. Exceptions include barium sulfate , calcium sulfate (sparingly soluble), and lead(II) sulfate , where the 2+/2− pairing leads to high lattice energies. For similar reasons, most metal carbonates are not soluble in water. Some soluble carbonate salts are: sodium carbonate , potassium carbonate and ammonium carbonate .
Strong salts or strong electrolyte salts are chemical salts composed of strong electrolytes . These salts dissociate completely or almost completely in water . They are generally odorless and nonvolatile .
Strong salts start with Na__, K__, NH 4 __, or they end with __NO 3 , __ClO 4 , or __CH 3 COO. Most group 1 and 2 metals form strong salts. Strong salts are especially useful when creating conductive compounds as their constituent ions allow for greater conductivity. [ citation needed ]
Weak salts or weak electrolyte salts are composed of weak electrolytes . These salts do not dissociate well in water. They are generally more volatile than strong salts. They may be similar in odor to the acid or base they are derived from. For example, sodium acetate , CH 3 COONa, smells similar to acetic acid CH 3 COOH.
Salts are characteristically insulators . Although they contain charged atoms or clusters, these materials do not typically conduct electricity to any significant extent when the substance is solid. In order to conduct, the charged particles must be mobile rather than stationary in a crystal lattice . This is achieved to some degree at high temperatures when the defect concentration increases the ionic mobility and solid state ionic conductivity is observed. When the salts are dissolved in a liquid or are melted into a liquid , they can conduct electricity because the ions become completely mobile. For this reason, molten salts and solutions containing dissolved salts (e.g., sodium chloride in water) can be used as electrolytes . [ 75 ] This conductivity gain upon dissolving or melting is sometimes used as a defining characteristic of salts. [ 76 ]
In some unusual salts: fast-ion conductors , and ionic glasses , [ 53 ] one or more of the ionic components has a significant mobility, allowing conductivity even while the material as a whole remains solid. [ 77 ] This is often highly temperature dependent, and may be the result of either a phase change or a high defect concentration. [ 77 ] These materials are used in all solid-state supercapacitors , batteries , and fuel cells , and in various kinds of chemical sensors . [ 78 ] [ 79 ]
The colour of a salt is often different from the colour of an aqueous solution containing the constituent ions, [ 80 ] or the hydrated form of the same compound. [ 13 ]
The anions in compounds with bonds with the most ionic character tend to be colorless (with an absorption band in the ultraviolet part of the spectrum). [ 81 ] In compounds with less ionic character, their color deepens through yellow, orange, red, and black (as the absorption band shifts to longer wavelengths into the visible spectrum). [ 81 ]
The absorption band of simple cations shifts toward a shorter wavelength when they are involved in more covalent interactions. [ 81 ] This occurs during hydration of metal ions, so colorless anhydrous salts with an anion absorbing in the infrared can become colorful in solution. [ 81 ]
Salts exist in many different colors , which arise either from their constituent anions, cations or solvates . For example:
Some minerals are salts, some of which are soluble in water. [ dubious – discuss ] [ clarification needed ] Similarly, inorganic pigments tend not to be salts, because insolubility is required for fastness. Some organic dyes are salts, but they are virtually insoluble in water.
Salts can elicit all five basic tastes , e.g., salty ( sodium chloride ), sweet ( lead diacetate , which will cause lead poisoning if ingested), sour ( potassium bitartrate ), bitter ( magnesium sulfate ), and umami or savory ( monosodium glutamate ).
Salts of strong acids and strong bases (" strong salts ") are non- volatile and often odorless, whereas salts of either weak acids or weak bases (" weak salts ") may smell like the conjugate acid (e.g., acetates like acetic acid ( vinegar ) and cyanides like hydrogen cyanide ( almonds )) or the conjugate base (e.g., ammonium salts like ammonia ) of the component ions. That slow, partial decomposition is usually accelerated by the presence of water, since hydrolysis is the other half of the reversible reaction equation of formation of weak salts.
Salts have long had a wide variety of uses and applications. Many minerals are ionic. [ 82 ] Humans have processed common salt (sodium chloride) for over 8000 years, using it first as a food seasoning and preservative, and now also in manufacturing, agriculture , water conditioning, for de-icing roads, and many other uses. [ 83 ] Many salts are so widely used in society that they go by common names unrelated to their chemical identity. Examples of this include borax , calomel , milk of magnesia , muriatic acid , oil of vitriol , saltpeter , and slaked lime . [ 84 ]
Soluble salts can easily be dissolved to provide electrolyte solutions. This is a simple way to control the concentration and ionic strength . The concentration of solutes affects many colligative properties , including increasing the osmotic pressure , and causing freezing-point depression and boiling-point elevation . [ 85 ] Because the solutes are charged ions they also increase the electrical conductivity of the solution. [ 86 ] The increased ionic strength reduces the thickness of the electrical double layer around colloidal particles, and therefore the stability of emulsions and suspensions . [ 87 ]
The chemical identity of the ions added is also important in many uses. For example, fluoride containing compounds are dissolved to supply fluoride ions for water fluoridation . [ 88 ]
Solid salts have long been used as paint pigments, and are resistant to organic solvents, but are sensitive to acidity or basicity. [ 89 ] Since 1801 pyrotechnicians have described and widely used metal-containing salts as sources of colour in fireworks. [ 90 ] Under intense heat, the electrons in the metal ions or small molecules can be excited. [ 91 ] These electrons later return to lower energy states, and release light with a colour spectrum characteristic of the species present. [ 92 ] [ 93 ]
In chemical synthesis , salts are often used as precursors for high-temperature solid-state synthesis. [ 94 ]
Many metals are geologically most abundant as salts within ores . [ 95 ] To obtain the elemental materials, these ores are processed by smelting or electrolysis , in which redox reactions occur (often with a reducing agent such as carbon) such that the metal ions gain electrons to become neutral atoms. [ 96 ] [ 97 ]
According to the nomenclature recommended by IUPAC , salts are named according to their composition, not their structure. [ 98 ] In the most simple case of a binary salt with no possible ambiguity about the charges and thus the stoichiometry , the common name is written using two words. [ 99 ] The name of the cation (the unmodified element name for monatomic cations) comes first, followed by the name of the anion. [ 100 ] [ 101 ] For example, MgCl 2 is named magnesium chloride , and Na 2 SO 4 is named sodium sulfate ( SO 2− 4 , sulfate , is an example of a polyatomic ion ). To obtain the empirical formula from these names, the stoichiometry can be deduced from the charges on the ions, and the requirement of overall charge neutrality. [ 102 ]
If there are multiple different cations and/or anions, multiplicative prefixes ( di- , tri- , tetra- , ...) are often required to indicate the relative compositions, [ 103 ] and cations then anions are listed in alphabetical order. [ 104 ] For example, KMgCl 3 is named magnesium potassium trichloride to distinguish it from K 2 MgCl 4 , magnesium dipotassium tetrachloride [ 105 ] (note that in both the empirical formula and the written name, the cations appear in alphabetical order, but the order varies between them because the symbol for potassium is K). [ 106 ] When one of the ions already has a multiplicative prefix within its name, the alternate multiplicative prefixes ( bis- , tris- , tetrakis- , ...) are used. [ 107 ] For example, Ba(BrF 4 ) 2 is named barium bis(tetrafluoridobromate) . [ 108 ]
Compounds containing one or more elements which can exist in a variety of charge/ oxidation states will have a stoichiometry that depends on which oxidation states are present, to ensure overall neutrality. This can be indicated in the name by specifying either the oxidation state of the elements present, or the charge on the ions. [ 108 ] Because of the risk of ambiguity in allocating oxidation states, IUPAC prefers direct indication of the ionic charge numbers. [ 108 ] These are written as an arabic integer followed by the sign (... , 2−, 1−, 1+, 2+, ...) in parentheses directly after the name of the cation (without a space separating them). [ 108 ] For example, FeSO 4 is named iron(2+) sulfate (with the 2+ charge on the Fe 2+ ions balancing the 2− charge on the sulfate ion), whereas Fe 2 (SO 4 ) 3 is named iron(3+) sulfate (because the two iron ions in each formula unit each have a charge of 3+, to balance the 2− on each of the three sulfate ions). [ 108 ] Stock nomenclature , still in common use, writes the oxidation number in Roman numerals (... , −II, −I, 0, I, II, ...). So the examples given above would be named iron(II) sulfate and iron(III) sulfate respectively. [ 109 ] For simple ions the ionic charge and the oxidation number are identical, but for polyatomic ions they often differ. For example, the uranyl(2+) ion, UO 2+ 2 , has uranium in an oxidation state of +6, so would be called a dioxouranium(VI) ion in Stock nomenclature. [ 110 ] An even older naming system for metal cations, also still widely used, appended the suffixes -ous and -ic to the Latin root of the name, to give special names for the low and high oxidation states. [ 111 ] For example, this scheme uses "ferrous" and "ferric", for iron(II) and iron(III) respectively, [ 111 ] so the examples given above were classically named ferrous sulfate and ferric sulfate . [ citation needed ]
Common salt-forming cations include:
Common salt-forming anions (parent acids in parentheses where available) include:
Salts with varying number of hydrogen atoms replaced by cations as compared to their parent acid can be referred to as monobasic , dibasic , or tribasic , identifying that one, two, or three hydrogen atoms have been replaced; polybasic salts refer to those with more than one hydrogen atom replaced. Examples include:
Zwitterions contain an anionic and a cationic centre in the same molecule , but are not considered salts. Examples of zwitterions are amino acids , many metabolites , peptides , and proteins . [ 112 ] | https://en.wikipedia.org/wiki/Salt_(chemistry) |
The Salt River Project ( SRP ) encompasses two separate entities: the Salt River Project Agricultural Improvement and Power District , an agency of the state of Arizona that serves as an electrical utility for the Phoenix metropolitan area , and the Salt River Valley Water Users' Association , a utility cooperative that serves as the primary water provider for much of central Arizona. It is one of the primary public utility companies in Arizona.
SRP is not related to the Rio Salado Project ( Rio Salado is Spanish for Salt River ), a series of improvement projects along the Salt River through the Phoenix Metropolitan Area.
SRP serves large portions of the Phoenix metropolitan area.
Each company of SRP is governed separately.
For the Association, landowners elect a president, a vice president, a 10-member board of governors and 30 council members.
For the District, landowners elect a president, a vice president, a 14-member board of directors and 30 council members.
The officials of each organization are elected on the first Tuesday in April of even-numbered years. The last scheduled Association and District elections were held on April 7, 2020. [ needs update ] Both are elected by all landowners in the SRP service area through a "debt-proportionate" system. For instance, a person who owns five acres casts five votes.
The Hohokam , the ancestors of the Salt River Pima-Maricopa Indian and Gila River Indian communities, built canals spanning nearly 500 miles. The SRP canal system follows much of the ancient canal network. [ 2 ]
Early settlers in Phoenix and nearby areas were forced to rely on the flow of the Salt River to sustain agricultural activities. The river was prone to both floods and droughts and proved to be a less than reliable resource for the settlers. Failed plans to build a dam on the river in 1897, [ 3 ] combined with a series of droughts, heightened the need for controlling the river.
With the passage of the National Reclamation Act of 1902 , funding for reclamation projects with low-interest government loans paved the way for the creation of the Salt River Valley Water Users' Association the following year. Over 200,000 acres (81,000 ha) of private land belonging to the ranchers and farmers in the association were pledged for collateral and the association was officially incorporated February 7, 1903, becoming the first multipurpose project started under the reclamation act. [ 4 ] Following on March 14, 1903, this project was one of the first five reclamation projects approved, under the Act, by the Secretary of the Interior. [ 5 ] Construction on the Roosevelt Dam would commence the following year.
Although the construction of dams was the association's most visible and costly project, an integral part of the effort was also the construction and improvement of a system of canals designed to distribute the water from the Salt River among the various members living in the valley.
Hydroelectricity was produced at the dam site during construction, and used for the manufacture of cement and other purposes. In 1906 (before the dam was completed) electricity began to be produced from a hydroelectric generator within the dam. Almost all of the electricity not needed for agriculture, including the majority of that used in Phoenix, was sold to PG&E under an agreement that prohibited the United States Bureau of Reclamation from selling retail electricity within the city. [ 6 ]
In 1936, the Arizona Legislature allowed for the creation of governmental districts that could finance large-scale agricultural projects with tax-free bonds. [ 7 ] Shortly thereafter, the Salt River Project Agricultural Improvement and Power District was created, the second half of SRP as it exists today. Over the next several decades, a series of major improvements along the Salt and Verde rivers would raise the number of reservoirs in the district to six, and at the same time SRP was constructing and maintaining a number of other electrical generating stations throughout the state.
As of 2007, SRP owns or operates eleven electrical generating stations, seven hydroelectric plants, and has energy purchasing agreements with four major hydroelectric stations along the Colorado River , making them a major provider of electric service in the Phoenix area. Along with the six reservoirs along the Salt and Verde rivers , SRP operates dams at the Blue Ridge Reservoir as well as the Granite Reef Diversion Dam and a number of canals, making the SRP a major provider of water to the Phoenix area.
SRP owns and operates four reservoirs along the Salt River east of Phoenix. The main function of these reservoirs is to serve as water storage for the Phoenix metropolitan area, with a total capacity of 3,292,054 acre feet .
These reservoirs also serve as important recreational centers. The lakes are regularly stocked with fish, and are supplied with boat ramps for both angling and other watersports.
Theodore Roosevelt Dam and the Roosevelt Lake it forms are considered perhaps the crowning achievements of SRP. With the initial funds raised by the association in 1903, an ambitious project was begun several miles east of Phoenix in the Tonto Valley, at the confluence of the Tonto Creek and the Salt River. At its completion in 1911, Roosevelt Dam was the tallest masonry dam in the world at 280 feet (85 m). [ 8 ] It was dedicated by U.S. President Theodore Roosevelt , for whom the dam and the reservoir are named. [ 9 ]
In 1996, a massive expansion project aimed at increasing the capacity of the lake was finished. The dam was resurfaced with concrete and raised an additional 77 feet (23 m), which had the effect of increasing the lake's capacity by over 20%, and providing much needed flood control space on the Salt River. Shortly after completion, however, the area entered into a prolonged period of drought, and it would be some time before the new capacity was used, with the lake finally reaching historic levels of 90% capacity in early 2005. [ 10 ]
With an at-capacity surface area of nearly 21,500 acres (8,700 ha), Roosevelt is the largest lake that is wholly inside the state of Arizona. It can store 2,910,200 acre-feet (3.5897 × 10 9 m 3 ) of water at capacity. [ 11 ]
Apache Lake was formed by the construction of the Horse Mesa Dam , finished in 1927. Several miles downstream from Roosevelt, the dam stands 300 feet (91 m) high. The lake itself is considerably smaller than Roosevelt at only 2,600 acres (1,100 ha) of surface area at full capacity, and can store 254,138 acre-feet (313,475,000 m 3 ) of water. [ 12 ]
Like the rest of the Salt River lakes downstream from Roosevelt, Apache Lake is long and narrow, filling the bottom of the canyon it resides in. It does have a hydroelectric generating station.
Canyon Lake , the third lake on the Salt River, is created by the Mormon Flat Dam . The dam was completed in 1925, being the second of the dams to be completed. The dam is named for a nearby geographical feature, a flat campground where Mormon pioneers from Utah would often stop on their journey to the Phoenix area. Downstream from Apache Lake, it is considerably smaller with only 950 acres (380 ha) of surface area when full, holding 57,852 acre-feet (71,359,000 m 3 ). Like the other Salt River dams, it is equipped with hydroelectric generators. [ 13 ]
Saguaro Lake is formed by the Stewart Mountain Dam , downstream from Canyon Lake. Completed in 1930, it was the last of the reservoirs to be built on the Salt River. It is somewhat larger than Canyon but smaller than the others, having a surface area of 1,280 acres (520 ha) when full, holding 69,765 acre-feet (86,054,000 m 3 ). The dam is equipped with hydroelectric generators. [ 14 ]
After completion of the four dams on the Salt River, SRP turned to the smaller Verde River for further expansion of the project. Like the reservoirs on the Salt, the Verde reservoirs are used for recreational purposes as well as water storage and flood control.
The first of the lakes on the Verde River was created with the construction of the Bartlett Dam , finishing in 1939. At 308.5 feet (94 m) tall, the multiple-arch dam is lacking in hydroelectric generating capabilities, unlike most dams on the Salt River. Bartlett Lake , with 2,700 acres (1,100 ha) of surface area at capacity, is larger than all the Salt River reservoirs save Roosevelt. When full the lake can hold 178,186 acre-feet (219,789,000 m 3 ) of water.
Horseshoe Lake is formed by Horseshoe Dam and was finished in 1946, upstream from Lake Bartlett. Unlike the other dams built to this point, the construction was done by the Phelps Dodge Corporation as part of a water exchange agreement. In 1949, the city of Phoenix funded the construction of spillway gates for the dam in exchange for water rights for city users. Like Bartlett, this dam does not have hydroelectric generating capabilities. At 2,800 acres (1,100 ha) in surface area when full it is slightly larger than Bartlett but has a smaller total capacity, holding only 131,427 acre-feet (162,113,000 m 3 ) at maximum.
Phelps Dodge, Inc., a large mining company in Arizona, constructed the Blue Ridge Dam (now named C.C. Cragin) in 1965 to help meet its water needs. A water exchange agreement penned three years earlier promised the facilities to SRP, and in 2005 SRP took possession of the dam and water production facilities. Located on the Mogollon Rim , C.C. Cragin is not on the Salt or Verde rivers but is a part of the general watershed covered in the SRP area. The small lake has a storage capacity of only 15,000 acre-feet (19,000,000 m 3 ) of water and is used to augment the water supply for the Gila River Indian Community, northern Gila County and the town of Payson.
The Granite Reef Diversion Dam , constructed near the confluence of the Salt and Verde rivers, does not actually hold back a reservoir but is used to divert water from those rivers into the system of canals feeding into the Phoenix area. It was actually the first of the dams constructed, finished in 1906 to replace the Arizona Dam, which had been washed away by floods the previous year.
SRP operates canals running in a network through much of the southern half of the Phoenix metropolitan area that distributes water from the Salt River system. Major canals operated by SRP are:
SRP also operates flood control canals throughout the Phoenix area.
Besides the power generated at several of the dams along the Salt River, SRP owns or operates, in part, several power generating stations throughout the state:
Renee Eastman, representing Salt River Project, is on the 2013-2014 Board of Directors for the Public Affairs Council (PAC). [ 15 ] [ 16 ]
Salt River Project is a Gold Sponsor for the National Conference of State Legislatures (NCSL). [ 17 ]
Peter Hayes, an Associate General Manager at SRP, is on the board of directors of the Greater Phoenix Chamber of Commerce (GPCC). [ 18 ]
Salt River Project has been a member of the Greater Phoenix Chamber of Commerce (GPCC) since 1940. [ 19 ]
Molly Greene, is on the board of directors of the Arizona Chamber of Commerce and Industry serving as the Chair of Public Affairs Committee. [ 20 ]
Salt River Project is an "Arizona Trustee" member of the Arizona Chamber of Commerce and Industry . [ 21 ]
Russell Smoldon, representing Salt River Project, is on the board of directors for the Greater Phoenix Urban League [ 22 ]
Salt River Project is a member of the Electric Power Research Institute (EPRI). [ 23 ]
Salt River Project is a member of the Large Public Power Council (LPPC). [ 24 ]
Salt River Project is a member of the American Public Power Association (APPA). [ 25 ]
Salt River Project is a member of the Labor and Management Public Affairs Committee (LAMPAC), a utility labor organization. [ 26 ]
Salt River Project sponsored programming on the order of $15,000 between 2006 and 2009 to the Democratic Attorneys General Association. [ 27 ]
Salt River Project took part in several energy-related initiatives for and through the Western Governors Association (WGA). [ 28 ]
Salt River Project is a member of the Associates program of the Council of State Governments (CSG). [ 29 ]
Russell Smolden, representing Salt River Project, sits on the Private Enterprise Board of the American Legislative Exchange Council (ALEC). [ 30 ] | https://en.wikipedia.org/wiki/Salt_River_Project |
The salt and ice challenge is an Internet challenge in which participants pour salt on their bodies, usually on the arm, and ice is then placed on the salt. [ 1 ] This causes a "burning" sensation similar to frostbite , and participants vie to withstand the pain for the longest time. The challenge can be recorded and posted on YouTube or other forms of social media . [ 2 ]
The ice and salt create an eutectic frigorific mixture which can get as cold as −18 °C (0 °F). [ 3 ]
The stunt can quickly cause second- and third-degree injuries similar to frostbite or being burnt with the metal end of a lighter , as well as causing painful open sores to form on the skin. Due to the numbing sensation of the cold and possible nerve damage during the stunt, participants are often unaware of the extent of any injuries sustained during the challenge, only feeling pain once the salt on their skin enters lesions created during the challenge. Skin discoloration from the challenge may remain after the challenge has been attempted. [ 4 ] [ 5 ] [ 6 ]
The salt and ice form an eutectic frigorific mixture. Molecular polarity is key to this reaction. The ions in sodium chloride (table salt) are heavily influenced by the molecular polarizability of the ice. [ 7 ] The difference between the spacing of the electrons in the table salt and ice causes this reaction. The melting point of ice is decreased due to the incorporation of table salt and this then causes a binding of the two substances. The ice is neutralized by the salt, thus causing the ice to melt more easily and quickly. [ 8 ]
The stunt leaves behind an ice burn that increases in severity the longer the chemical reaction on the skin continues. In this ice burn, the ice crystals that form have the potential to burn and scar the skin permanently. Blistering at the site of injury is common in more severe cases. [ 9 ] The freezing of tissue between the dermal and epidermal levels of the skin leads to a disruption in blood circulation, initially causing frost nip. [ 10 ] After a few days, depending on the severity and duration of the burn, epithelial cells should slowly regenerate along with scarring and surface disruption. [ 11 ]
The salt and ice challenge was popularized on YouTube and other social media in the late 2000s and early 2010s. The first documented video of the salt and ice challenge was posted to YouTube in 2006 by user OxZmoran. They performed the stunt and garnered over 100,000 views. [ 12 ] The first viral salt and ice challenge was posted to the entertainment site eBaum's World , in which a group of teenagers attempted the challenge and garnered almost 500,000 views. [ 13 ] This virality led to other popular influencers, YouTubers, and online personalities attempting the salt and ice challenge and posting the results online.
Due to the challenge's increase in popularity during the 2010s, many local and national news stations reported incidents of the challenge harming those involved and warning against it. CBS News reported a case in Pittsburgh in 2012 in which a teen received serious burns from attempting the challenge. [ 14 ] In 2017, ABC Action News described how many teens are influenced by online videos, and that by attempting these challenges they can be sent to the hospital. [ 15 ] Media talk shows such as the Today Show posted an article directed to parents of teens, highlighting the dangers of social media and virality when influencing those to try online challenges. [ 16 ]
This World Wide Web –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Salt_and_ice_challenge |
In chemistry , a salt bridge is a combination of two non-covalent interactions : hydrogen bonding and ionic bonding (Figure 1). Ion pairing is one of the most important noncovalent forces in chemistry, in biological systems, in different materials and in many applications such as ion pair chromatography . It is a most commonly observed contribution to the stability to the entropically unfavorable folded conformation of proteins. Although non-covalent interactions are known to be relatively weak interactions, small stabilizing interactions can add up to make an important contribution to the overall stability of a conformer. [ 1 ] Not only are salt bridges found in proteins, but they can also be found in supramolecular chemistry . The thermodynamics of each are explored through experimental procedures to access the free energy contribution of the salt bridge to the overall free energy of the state.
In water, formation of salt bridges or ion pairs is mostly driven by entropy, usually accompanied by unfavorable ΔH contributions on account of desolvation of the interacting ions upon association. [ 2 ] Hydrogen bonds contribute to the stability of ion pairs with e.g. protonated ammonium ions , and with anions is formed by deprotonation as in the case of carboxylate , phosphate etc; then the association constants depend on the pH. Entropic driving forces for ion pairing (in absence of significant H-bonding contributions) are also found in methanol as solvent. In nonpolar solvents contact ion pairs with very high association constants are formed; [ 3 ] [ 4 ] in the gas phase the association energies of e.g. alkali halides reach up to 200 kJ/mol. [ 5 ] The Bjerrum or the Fuoss equation describe ion pair association as function of the ion charges zA and zB and the dielectric constant ε of the medium; a corresponding plot of the stability ΔG vs. zAzB shows for over 200 ion pairs the expected linear correlation for a large variety of ions. [ 6 ] Inorganic as well as organic ions display at moderate ionic strength I similar salt bridge association ΔG values around 5 to 6 kJ/mol for a 1:1 combination of anion and cation, almost independent of the nature (size, polarizability etc) of the ions. [ 7 ] [ 8 ] The ΔG values are additive and approximately a linear function of the charges, the interaction of e.g. a doubly charged phosphate anion with a single charged ammonium cation accounts for about 2x5 = 10 kJ/mol. The ΔG values depend on the ionic strength I of the solution, as described by the Debye–Hückel equation , at zero ionic strength one observes ΔG = 8 kJ/mol. The stabilities of the alkali-ion pairs as function of the anion charge z by can be described by a more detailed equation. [ 9 ]
The salt bridge most often arises from the anionic carboxylate (RCOO − ) of either aspartic acid or glutamic acid and the cationic ammonium (RNH 3 + ) from lysine or the guanidinium (RNHC(NH 2 ) 2 + ) of arginine (Figure 2). [ 1 ] Although these are the most common, other residues with ionizable side chains such as histidine , tyrosine , and serine can also participate, depending on outside factors perturbing their p K a 's. The distance between the residues participating in the salt bridge is also cited as being important. The N-O distance required is less than 4 Å (400 pm). Amino acids greater than this distance apart do not qualify as forming a salt bridge. [ 11 ] Due to the numerous ionizable side chains of amino acids found throughout a protein, the pH at which a protein is placed is crucial to its stability.
Salt bridges also can form between a protein and small molecule ligands. Over 1100 unique protein-ligand complexes from the Protein Databank were found to form salt bridges with their protein targets, indicating that salt bridges are frequent in drug-protein interaction. [ 12 ] These contain structures from different enzyme classes, including hydrolase, transferases, kinases, reductase, oxidoreductase, lyases, and G protein-coupled receptors (GPCRs).
The contribution of a salt bridge to the overall stability to the folded state of a protein can be assessed through thermodynamic data gathered from mutagenesis studies and nuclear magnetic resonance techniques. [ 13 ] Using a mutated pseudo-wild-type protein specifically mutated to prevent precipitation at high pH, the salt bridge’s contribution to the overall free energy of the folded protein state can be determined by performing a point-mutation, altering and, consequently, breaking the salt bridge. For example, a salt bridge was identified to exist in the T4 lysozyme between aspartic acid (Asp) at residue 70 and a histidine (His) at residue 31 (Figure 3). Site-directed mutagenesis with asparagine (Asn) (Figure 4) was done obtaining three new mutants: Asp70Asn His31 (Mutant 1), Asp70 His31Asn (Mutant 2), and Asp70Asn His31Asn (Double Mutant).
Once the mutants have been established, two methods can be employed to calculate the free energy associated with a salt bridge. One method involves the observation of the melting temperature of the wild-type protein versus that of the three mutants. The denaturation can be monitored through a change in circular dichroism . A reduction in melting temperature indicates a reduction in stability. This is quantified through a method described by Becktel and Schellman where the free energy difference between the two is calculated through Δ T Δ S . [ 14 ] There are some issues with this calculation and can only be used with very accurate data. [ citation needed ] In the T4 lysozyme example, Δ S of the pseudo-wild-type had previously been reported at pH 5.5 so the midpoint temperature difference of 11 °C at this pH multiplied by the reported Δ S of 360 cal/(mol·K) (1.5 kJ/(mol·K)) yields a free energy change of about −4 kcal/mol (−17 kJ/mol). This value corresponds to the amount of free energy contributed to the stability of the protein by the salt bridge.
The second method utilizes nuclear magnetic resonance spectroscopy to calculate the free energy of the salt bridge. A titration is performed, while recording the chemical shift corresponding to the protons of the carbon adjacent to the carboxylate or ammonium group. The midpoint of the titration curve corresponds to the p K a , or the pH where the ratio of protonated: deprotonated molecules is 1:1. Continuing with the T4 lysozyme example, a titration curve is obtained through observation of a shift in the C2 proton of histidine 31 (Figure 5). Figure 5 shows the shift in the titration curve between the wild-type and the mutant in which Asp70 is Asn. The salt bridge formed is between the deprotonated Asp70 and protonated His31. This interaction causes the shift seen in His31’s p K a . In the unfolded wild-type protein, where the salt bridge is absent, His31 is reported to have a p K a of 6.8 in H 2 O buffers of moderate ionic strength. Figure 5 shows a p K a of the wild-type of 9.05. This difference in p K a is supported by the His31’s interaction with Asp70. To maintain the salt bridge, His31 will attempt to keep its proton as long as possible. When the salt bridge is disrupted, like in the mutant D70N, the p K a shifts back to a value of 6.9, much closer to that of His31 in the unfolded state.
The difference in p K a can be quantified to reflect the salt bridge’s contribution to free energy. Using Gibbs free energy : Δ G = − RT ln( K eq ), where R is the universal gas constant, T is the temperature in kelvins, and K eq is the equilibrium constant of a reaction in equilibrium. The deprotonation of His31 is an acid equilibrium reaction with a special K eq known as the acid dissociation constant , K a : His31-H + ⇌ His31 + H + . The p K a is then related to K a by the following: p K a = −log( K a ). Calculation of the free energy difference of the mutant and wild-type can now be done using the free energy equation, the definition of p K a , the observed p K a values, and the relationship between natural logarithms and logarithms. In the T4 lysozyme example, this approach yielded a calculated contribution of about 3 kcal/mol to the overall free energy. [ 13 ] A similar approach can be taken with the other participant in the salt bridge, such as Asp70 in the T4 lysozyme example, by monitoring its shift in p K a after mutation of His31.
A word of caution when choosing the appropriate experiment involves the location of the salt bridge within the protein. The environment plays a large role in the interaction. [ 15 ] At high ionic strengths, the salt bridge can be completely masked since an electrostatic interaction is involved. The His31-Asp70 salt bridge in T4 lysozyme was buried within the protein. Entropy plays a larger role in surface salt bridges where residues that normally have the ability to move are constricted by their electrostatic interaction and hydrogen bonding. This has been shown to decrease entropy enough to nearly erase the contribution of the interaction. [ 16 ] Surface salt bridges can be studied similarly to that of buried salt bridges, employing double mutant cycles and NMR titrations. [ 17 ] Although cases exist where buried salt bridges contribute to stability, like anything else, exceptions do exist and buried salt bridges can display a destabilizing effect. [ 11 ] Also, surface salt bridges, under certain conditions, can display a stabilizing effect. [ 15 ] [ 17 ] The stabilizing or destabilizing effect must be assessed on a case by case basis and few blanket statements are able to be made.
Supramolecular chemistry is a field concerned with non-covalent interactions between macromolecules. Salt bridges have been used by chemists within this field in both diverse and creative ways, including sensing of anions, the synthesis of molecular capsules and double helical polymers.
Major contributions of supramolecular chemistry have been devoted to recognition and sensing of anions. [ 18 ] [ 19 ] [ 20 ] [ 21 ] [ 22 ] [ 23 ] Ion pairing is the most important driving force for anion complexation, but selectivity e.g. within the halide series has been achieved, mostly by hydrogen bonds contributions.
Molecular capsules are chemical scaffolds designed to capture and hold a guest molecule (see molecular encapsulation ). Szumna and coworkers developed a novel molecular capsule with a chiral interior. [ 24 ] This capsule is made of two halves, like a plastic easter egg (Figure 6). Salt bridge interactions between the two halves cause them to self-assemble in solution (Figure 7). They are stable even when heated to 60 °C.
Yashima and coworkers have used salt bridges to construct several polymers that adopt a double helix conformation much like DNA . [ 25 ] In one example, they incorporated platinum to create a double helical metallopolymer. [ 26 ] Starting from their monomer and platinum(II) biphenyl (Figure 8), their metallopolymer self assembles through a series of ligand exchange reactions. The two halves of the monomer are anchored together through the salt bridge between the deprotonated carboxylate and the protonated nitrogens. | https://en.wikipedia.org/wiki/Salt_bridge_(protein_and_supramolecular) |
A salt lake or saline lake is a landlocked body of water that has a concentration of salts (typically sodium chloride ) and other dissolved minerals significantly higher than most lakes (often defined as at least three grams of salt per liter). [ 1 ] In some cases, salt lakes have a higher concentration of salt than sea water ; such lakes can also be termed hypersaline lake , and may also be pink lakes on account of their color. An alkalic salt lake that has a high content of carbonate is sometimes termed a soda lake . [ 2 ]
Salt lakes are classified according to salinity levels. The formation of these lakes is influenced by processes such as evaporation and deposition. Salt lakes face serious conservation challenges due to climate change, pollution and water diversion.
The primary method of classification for salt lakes involves assessing the chemical composition of the water within the lakes, specifically its salinity, pH , and the dominant ions present. [ 2 ]
Subsaline lakes have a salinity lower than that of seawater but higher than freshwater , typically ranging from 0.5 to 3 grams per liter (g/L). [ 2 ]
Hyposaline lakes exhibit salinities from 3 to 20 g/L, [ 3 ] which allows for the presence of freshwater species along with some salt-tolerant aquatic organisms. [ 2 ] Lake Alchichica in Mexico is a hyposaline lake. [ 4 ]
Mesosaline lakes have a salinity level ranging from 20 to 50 g/L. [ 3 ] [ 5 ] An example of a mesosaline lake is Redberry Lake in Saskatchewan, Canada . [ 5 ]
Hypersaline lakes possess salinities greater than 35 g/L, [ 2 ] [ 6 ] or 50 g/L, [ 3 ] often exceeding 200 g/L. The extreme salinity levels create harsh conditions that limit the diversity of life, primarily supporting specialized organisms such as halophilic bacteria and certain species of brine shrimp . [ 6 ] These lakes can have high concentrations of sodium salts and minerals, such as lithium, making such lakes vulnerable to mining interests. [ 6 ] Hypersaline lakes can be found in the McMurdo Dry Valleys in Antarctica, where salinity can reach ≈440‰. [ 7 ]
Salt lakes form through complex chemical, geological, and biological processes, influenced by environmental conditions like high evaporation rates and restricted water outflow. As water carrying dissolved minerals ( sodium , potassium , and magnesium ) enters these basins, it gradually evaporates, concentrating these minerals until they precipitate as salt deposits. [ 8 ] Then, specific ions interact under controlled temperatures, which leads to solid-solution formation and salt crystal deposition within the lake bed. [ 8 ] This cycle of evaporation and deposition is the main process to the unique saline environment that characterizes a salt lake. [ 8 ]
Environmental factors further shape the composition and formation of salt lakes. Seasonal variations in temperature and evaporation drive mineral saturation and promote salt crystallization . [ 9 ] In dry regions, water loss during warmer seasons concentrates the lake's salts. [ 9 ] This creates a dynamic environment where seasonal shifts affect the salt lake's mineral layers, contributing to its evolving structure and composition. [ 9 ] Groundwater rich in dissolved ions often serve as primary mineral sources that, combined with processes like evaporation and deposition, contribute to salt lake development. [ 10 ]
Salt lakes host a diverse range of animals, despite high levels of salinity acting as significant environmental constraints. [ 11 ] Increased salinity worsens oxygen levels and thermal conditions, raising the water's density and viscosity , which demands greater energy for animal movement. [ 11 ] Despite these challenges, salt lakes support biota adapted to such conditions with specialized physiological and biochemical mechanisms. [ 12 ] Common salt lake invertebrates include various parasites, with around 85 parasite species found in saline waters, including crustaceans and monogeneans . [ 11 ] Among them, the filter-feeding brine shrimp plays a crucial role as a keystone species by regulating phytoplankton and bacterioplankton levels. [ 13 ] The Artemia species also serves as an intermediate host for helminth parasites that affect migratory water birds like flamingos, grebes, gulls, shorebirds, and ducks. [ 13 ] Vertebrates in saline lakes include certain fish and bird species, though they are sensitive to fluctuations in salinity. [ 12 ] Many saline lakes are also alkaline, which imposes physiological challenges for fish, especially in managing nitrogenous waste excretion. [ 14 ] Fish species vary by lake; for instance, the Salton Sea is home to species such as carp, striped mullet, humpback sucker, and rainbow trout. [ 14 ]
Stratification in salt lakes occurs as a result of the unique chemical and environmental processes that cause water to separate into layers based on density . [ 15 ] In these lakes, high rates of evaporation often concentrate salts, leading to denser, saltier water sinking to the lake's bottom, while fresher water remains nearer the surface. [ 15 ] These seasonal changes influence the lake's structure, making stratification more pronounced during warmer months due to increasing evaporation, which drives separation between saline and fresher layers in the lake, leading a phenomenon known as meromixis (meromictic state), primarily prevents oxygen from penetrating the deeper layers and create the hypoxic (low oxygen) or anoxic (no oxygen) zones. [ 16 ] This separation eventually influenced the lake's chemistry, supporting only specialized microbial life adapted to extreme environments with high salinity and low oxygen levels. [ 17 ] The restricted vertical mixing limits nutrient cycling , creating a favorable ecosystem for halophiles (salt-loving organisms) that rely on these saline conditions for stability and balance. [ 17 ]
The extreme conditions within stratified salt lakes have a profound effect on aquatic life , as oxygen levels are severely limited due to the lack of vertical mixing. [ 17 ] Extremophiles , including specific bacteria and archaea , inhabit the hypersaline and oxygen-deficient zones at lower depths. [ 18 ] Bacteria and archaea, for example, rely on alternative metabolic processes that do not depend on oxygen. [ 18 ] These microorganisms play a critical role in nutrient cycling within salt lakes, as they break down organic material and release by-products that support other microbial communities. [ 18 ] Due to limited biodiversity, the restrictive environment limits biodiversity , allowing only specially adapted life forms to survive, which creates unique, highly specialized ecosystems that are distinct from freshwater or less saline habitats. [ 18 ]
Salt lakes have declined worldwide in recent years. The Aral Sea , once of the largest saline lakes with a surface area of 67,499 km in 1960, diminished to approximately 6,990 km in 2016. [ 19 ] This trend is not limited to the Aral Sea; salt lakes around the world are shrinking due to excessive water diversion, dam construction, pollution, urbanization, and rising temperatures associated with climate change. [ 19 ] The resulting declines cause severe disruptions to local ecosystems and biodiversity, degrades the environment, threatens economic stability, and displaces communities dependent on these lakes for resources and livelihood. [ 19 ]
In Utah, if the Great Salt Lake is not conserved, the state could face potential economic and public health crises, with consequences for air quality, local agriculture, and wildlife. [ 20 ] According to "Utah’s Great Salt Lake Strike Team", in order to increase the lake's level within the next 30 years, average inflows must increase by 472,00 acre-feet per year. This is approximately 33% more than the amount that has been reaching the lake in recent years. [ 21 ]
Water conservation is viewed as being the most cost-effective and practical strategy to save salt lakes like the Great Salt Lake. [ 21 ] Implementing strong water management policies, improving community awareness, and ensuring the return of water flow to these lakes are additional ways that may restore ecological balance. [ 21 ] Other proposed methods of maintaining lake levels include cloud seeding and the mitigation of dust transmission hotspots. [ 22 ]
Note: Some of the following are also partly fresh and/or brackish water. | https://en.wikipedia.org/wiki/Salt_lake |
High salt marsh dieback , or salt marsh browning, is the primary force in salt marsh degradation in the high marsh. The general effect is that the plants in the marsh die off and brown, leaving dead organic matter , and ultimately open sediment . Without strong plant roots holding the sediment, these open areas of land erode , causing the salt marsh to retreat back to the mainland. [ 1 ] Dieback zones lack their main producers, such as the salt marsh cord grass, or Spartina alterniflora , and ultimately become completely unproductive. [ 2 ]
Scientists have studied salt marsh dieback for decades, and they still argue about its causes. One of the main ideas suggests that salt marsh dieback is caused by waterlogging in S. alterniflora from increased submersion within the tides, increased sediment, and oxygen deficiency. [ 3 ] Other scientists have researched the possibility of increased soil salinity and decreased soil water as the causes for dieback. [ 4 ]
Salt marshes are important in preserving the brooding and nursery habitats of shellfish, fish, and insects.
Waterlogging is the result of too much water in a plant's root system and the surrounding soil, and usually occurs in the inland areas of the marsh. With the increase of surface water, waterlogged soils contain many reduced molecules, which can induce the accumulation of sulfide and other toxic compounds. [ 5 ] Current studies suggest that increased waterlogging is caused by sea level rise , a possible effect of global warming , which has many natural and anthropologic causes of its own. [ 6 ]
Salt marsh dieback results in the death of marsh-specific plants and the erosion of the landscape. One of the causes of waterlogging is the reduced aerobic respiration by the roots of S. alterniflora . It occurs mainly in the inland zones, though the streamside plants show partial anaerobic respiration.
Aerobic respiration takes sugars and oxygen to create carbon dioxide , water, and energy.
As aerobic respiration decreases, the plants become oxygen deficient, since the roots are unable to produce enough oxygen in the reduced soil conditions. Decreased oxygen uptake can also decrease plant productivity. [ 7 ]
To gain energy, these plants then go through a process of alcoholic fermentation (Mendelssohn et al. 1981). This fermentation process has an end product of carbon in the form of ethanol, which is diffused from the roots. Therefore, the plants are unable to use the diffused carbon, so the available plant energy decreases. [ 5 ]
Another product of waterlogging is the increase of sulfide in soil. The increase of sulfide is caused by anaerobic and aerobic bacteria, which are mainly seen in reduced soils. [ 6 ]
Increased sulfide has been shown to inhibit NH 4 -N ( ammoniacal nitrogen , an ammonium salt) uptake within the plant. [ 5 ] NH 4 -N is the most available form of nitrogen within the soil and it is a limiting nutrient in S. alterniflora productivity.
A higher concentration of NH 4 -N in the soil may show that the plant's uptake of NH 4 -N has decreased, leaving excess molecules in the soil. In addition, reduced soils can cause plant nitrification to decrease, leading to a greater lack of NH 4 -N uptake. [ 1 ]
Some scientists have found solutions to this problem. Mendelssohn and Kuhn set up an experiment with plants and soils in a Louisiana salt marsh in 2003. They found that when sediment deposits are increased within an unhealthy salt marsh area, the plants and soils are in better conditions.
The experiment showed that the plants with the greater sediment levels had more plant cover, with higher plants and a greater bulk density . The surface elevation increased with the increase of sediment, therefore reducing flooding. The roots could respire aerobically, so they did not have to rely on fermentation for energy. The plants with more sediment also showed a decrease in sulfide and NH 4 -N concentrations in the soil. Mendelssohn postulates that since the concentration of NH 4 -N decreased after the addition of sediment, more of the nitrogen was used by the plants. [ 6 ]
A second hypothesis of salt marsh dieback focuses on increased salinity and lack of soil water being the main causes of salt marsh dieback. Some scientists see this hypothesis as relevant, since global warming suggests that increased global temperatures may lead to increased evaporation and transpiration .
Brown and Pezeshki devised an experiment in which many S. alterniflora individuals were put under situations of increased salinity, increased water stress, and then a combined treatment. They found that those plants that experienced the combined treatment exhibited an increase in water stress, where plants are unable to get a sufficient amount of water from the soil, a decrease in photosynthetic activity, and ultimately death (Brown & Pezeshki 2007). | https://en.wikipedia.org/wiki/Salt_marsh_dieback |
A salt metathesis reaction is a chemical process involving the exchange of bonds between two reacting chemical species which results in the creation of products with similar or identical bonding affiliations. [ 1 ] This reaction is represented by the general scheme:
In older literature, the term double decomposition is common. The term double decomposition is more specifically used when at least one of the substances does not dissolve in the solvent , as the ligand or ion exchange takes place in the solid state of the reactant. For example:
Salt metathesis is a common technique for exchanging counterions . The choice of reactants is guided by a solubility chart or lattice energy . HSAB theory can also be used to predict the products of a metathesis reaction.
Salt metathesis is often employed to obtain salts that are soluble in organic solvents. Illustrative is the conversion of sodium perrhenate to the tetrabutylammonium salt : [ 2 ]
The tetrabutylammonium salt precipitates from the aqueous solution. It is soluble in dichloromethane .
Salt metathesis can be conducted in nonaqueous solution, illustrated by the conversion of ferrocenium tetrafluoroborate to a more lipophilic salt containing the tetrakis(pentafluorophenyl)borate anion: [ 3 ]
When the reaction is conducted in dichloromethane , the salt NaBF 4 precipitates and the B(C 6 F 5 ) 4 - salt remains in solution.
Metathesis reactions can occur between two inorganic salts when one product is insoluble in water. For example, the precipitation of silver chloride from a mixture of silver nitrate and cobalt hexammine chloride delivers the nitrate salt of the cobalt complex:
The reactants need not be highly soluble for metathesis reactions to take place. For example barium thiocyanate forms when boiling a slurry of copper(I) thiocyanate and barium hydroxide in water:
Metal complexes are alkylated via salt metathesis reactions. Illustrative is the methylation of titanocene dichloride to give the Petasis reagent : [ 4 ]
The salt product typically precipitates from the reaction solvent.
A neutralization reaction is a type of double replacement reaction. A neutralization reaction occurs when an acid reacts with an equal amount of a base . This reaction usually produces a salt. One example, hydrochloric acid reacts with disodium iron tetracarbonyl to produce the iron dihydride:
Reaction between an acid and a carbonate or bicarbonate salt yields carbonic acid , which spontaneously decomposes into carbon dioxide and water. The release of carbon dioxide gas from the reaction mixture drives the reaction to completion. For example, a common, science-fair "volcano" reaction involves the reaction of hydrochloric acid with sodium carbonate :
In contrast to salt metathesis reactions, which are driven by the precipitation of solid salts, are salt-free reductions , which are driven by formation of silyl halides, Salt-free metathesis reactions proceed homogeneously. [ 5 ] | https://en.wikipedia.org/wiki/Salt_metathesis_reaction |
Natural salt pans or salt flats are flat expanses of ground covered with salt and other minerals , usually shining white under the sun . They are found in deserts and are natural formations (unlike salt evaporation ponds , which are artificial).
A salt pan forms by evaporation of a water pool, such as a lake or pond . This happens in climates where the rate of water evaporation exceeds the rate of precipitation — that is, in a desert. If the water cannot drain into the ground, it remains on the surface until it evaporates, leaving behind minerals precipitated from the salt ions dissolved in the water. Over thousands of years , the minerals (usually salts) accumulate on the surface. [ 1 ] These minerals reflect the sun's rays and often appear as white areas.
Salt pans can be dangerous. The crust of salt can conceal a quagmire of mud that can engulf a truck. The Qattara Depression in the eastern Sahara Desert contains many such traps which served as strategic barriers during World War II . [ 2 ]
The Bonneville Salt Flats in Utah , where many land speed records have been set, are a well-known salt pan in the arid regions of the western United States .
The Etosha pan , in the Etosha National Park in Namibia , is another prominent example of a salt pan.
The Salar de Uyuni in Bolivia is the largest salt pan in the world. As of 2024, with an estimated 23 million tons , Bolivia holds about 22% of the world's known lithium resources (105 million tons); most of those are in the Salar de Uyuni. [ 3 ] The large area, clear skies, and exceptional flatness of the surface make the Salar an ideal object for calibrating the altimeters of Earth observation satellites. [ 4 ] [ 5 ]
Parts of Rann of Kutch (India) are salt marsh in the wet season and salt pan in the dry season. [ 6 ] | https://en.wikipedia.org/wiki/Salt_pan_(geology) |
The salt spray test (or salt fog test ) is a standardized and popular corrosion test method, used to check corrosion resistance of materials and surface coatings . Usually, the materials to be tested are metallic (although stone, ceramics, and polymers may also be tested) and finished with a surface coating which is intended to provide a degree of corrosion protection to the underlying metal.
Salt spray testing is an accelerated corrosion test that produces a corrosive attack to coated samples in order to evaluate (mostly comparatively) the suitability of the coating for use as a protective finish. The appearance of corrosion products ( rust or other oxides) is evaluated after a predetermined period of time. Test duration depends on the corrosion resistance of the coating; generally, the more corrosion resistant the coating is, the longer the period of testing before the appearance of corrosion or rust.
The salt spray test is one of the most widespread and long-established corrosion tests. ASTM B117 was the first internationally recognized salt spray standard, originally published in 1939. Other important relevant standards are ISO 9227, JIS Z 2371 and ASTM G85.
Salt spray testing is popular because it is relatively inexpensive, quick, well standardized, and reasonably repeatable. Although there may be a weak correlation between the duration in salt spray test and the expected life of a coating in certain coatings such as hot-dip galvanized steel , this test has gained worldwide popularity due to low cost and quick results. Most salt spray chambers today are not being used to predict the corrosion resistance of a coating, but to maintain coating processes such as pre-treatment and painting, electroplating, galvanizing, and the like, on a comparative basis. For example, pre-treated + painted components must pass 96 hours Neutral Salt Spray, to be accepted for production. Failure to meet this requirement implies instability in the chemical process of the pre-treatment, or the paint quality, which must be addressed immediately so that the upcoming batches are of the desired quality. The longer the accelerated corrosion test, the longer the process remains out of control, and larger is the loss in the form of non-conforming batches.
The principal application of the salt spray test is, therefore, enabling quick comparisons to be made between actual and expected corrosion resistance . Most commonly, the time taken for oxides to appear on the samples under test is compared to expectations, to determine whether the test is passed or failed. For this reason, the salt spray test is most often deployed in a quality audit role, where, for example, it can be used to check the effectiveness of a production process, such as the surface coating of a metallic part.
The salt spray test has little application in predicting how materials or surface coatings will resist corrosion in the real world, because it does not create, replicate or accelerate real-world corrosive conditions. Cyclic corrosion testing is better suited to this.
The apparatus for testing consists of a closed testing cabinet/chamber, where a salt water (5% NaCl) solution is atomized by means of spray nozzle(s) using pressurized air. This produces a corrosive environment of dense salt water fog (also referred to as a mist or spray) in the chamber, so that test samples exposed to this environment are subjected to severely corrosive conditions. Chamber volumes vary from supplier to supplier. If there is a minimum volume required by a particular salt spray test standard, this will be clearly stated and should be complied with. There is a general historical consensus that larger chambers can provide a more homogeneous testing environment.
Variations to the salt spray test solutions depend upon the materials to be tested. The most common test for steel based materials is the Neutral Salt Spray test (often abbreviated to NSS) which reflects the fact that this type of test solution is prepared to a neutral pH of 6.5 to 7.2. To maintain a neutral pH, hydrochloric acid or sodium hydroxide are added to reduce or increase pH into the required range. Results are represented generally as testing hours in NSS without appearance of corrosion products (e.g. 720 h in NSS according to ISO 9227). Synthetic seawater solutions are also commonly specified by some companies and standards. Other test solutions have other chemicals added including acetic acid (often abbreviated to ASS) and acetic acid with copper chloride (often abbreviated to CASS) each one chosen for the evaluation of decorative coatings, such as electroplated copper-nickel-chromium, electroplated copper-nickel or anodized aluminum . These acidified test solutions generally have a pH of 3.1 to 3.3
Some sources do not recommend using ASS or CASS test cabinets interchangeably for NSS tests, due to the risk of cross- contamination . It is claimed that a thorough cleaning of the cabinet after CASS test is very difficult. ASTM does not address this issue, but ISO 9227 does not recommend it and if it is to be done, advocates a thorough cleaning.
Although the majority of salt spray tests are continuous, i.e.; the samples under test are exposed to the continuous generation of salt fog for the entire duration of the test, a few do not require such exposure. Such tests are commonly referred to as modified salt spray tests. ASTM G85 is an example of a test standard which contains several modified salt spray tests which are variations to the basic salt spray test.
ASTM G85 [ 1 ] is the most popular global test standard covering modified salt spray tests. There are five such tests altogether, referred to in ASTM G85 as annexes A1 through to A5.
Many of these modified tests originally arose within particular industry sector , in order to address the need for a corrosion test capable of replicating the effects of naturally occurring corrosion and accelerate these effects.
This acceleration arises through the use of chemically altered salt spray solutions, often combined with other test climates and in most cases, the relatively rapid cycling of these test climates over time. Although popular in certain industries, modified salt spray testing has in many cases been superseded by cyclic corrosion testing (CCT)
The type of environmental test chambers used for modified salt spray testing to ASTM G85 are generally similar to the chambers used for testing to ASTM B117 , but will often have some additional features, such as an automatic climate cycling control system.
ASTM G85 Annex A1 – Acetic Acid Salt Spray Test (non-cyclic) This test can be used to determine the relative resistance to corrosion of decorative chromium plating on steel and zinc based die casting when exposed to an acetic acid salt spray climate at an elevated temperature. This test is also referred to as an ASS test.
Test specimens are placed in an enclosed chamber and exposed to a continuous indirect spray of salt water solution, prepared in accordance with the requirements of the test standard and acidified (pH 3.1–3.3) by the addition of acetic acid. This spray is set to fall-out on to the specimens at a rate of 1–2 ml/80 cm 2 /hour, in a chamber temperature of 35 °C. This climate is maintained under constant steady state conditions. The test duration is variable. [ 2 ]
ASTM G85 Annex A2 – Acidified Salt Fog Test (cyclic).
This test can be used to test the relative resistance to corrosion of aluminium alloys when exposed to a changing climate of acetic acid salt spray, followed by air drying, followed by high humidity, all at an elevated temperature. This test is also referred to as a MASTMAASIS test.
Test specimens are placed in an enclosed chamber, and exposed to a changing climate that comprises the following 3 part repeating cycle. 0.75 hours exposure to a continuous indirect spray of salt water solution, prepared in accordance with the requirements of the test standard and acidified (pH 2.8–3.0) by the addition of acetic acid. This spray is set to fall-out on to the specimens at a rate of 1–2 ml/80 cm 2 /hour. This is followed by a 2 hour exposure to an air drying (purge) climate. This is followed by 3.25 hours exposure to a high humidity climate which gradually rises to between 65% RH and 95% RH. The entire test cycle is at a constant chamber temperature of 49 °C. The number of cycle repeats and therefore the test duration is variable. [ 2 ]
ASTM G85 Annex A3 – Seawater Acidified Test (cyclic)
This test can be used to test the relative resistance to corrosion of coated or uncoated aluminium alloys and other metals, when exposed to a changing climate of acidified synthetic seawater spray, followed by a high humidity, both at an elevated temperature. This test is also referred to as a SWAAT test.
Test specimens are placed in an enclosed chamber, and exposed to a changing climate that comprises the following 2 part repeating cycle. First, a 30 minute exposure to a continuous indirect spray of synthetic seawater solution, prepared in accordance with the requirements of the test standard and acidified (pH 2.8–3.0) by the addition of acetic acid. This spray is set to fall-out on to the specimens at a rate of 1–2 ml/80 cm 2 /hour. This is followed by a 90 minute exposure to a high humidity climate (above 98% RH). The entire test cycle is at a constant chamber temperature of 49 °C (may be reduced to 24–35 °C for organically coated specimens). The number of cycle repeats and therefore the test duration is variable. [ 2 ]
ASTM G85 Annex A4 – SO 2 Salt Spray Test (cyclic)
This test can be used to test the relative resistance to corrosion of product samples that are likely to encounter a combined SO 2 /salt spray/acid rain environment during their usual service life.
Test specimens are placed in an enclosed chamber, and exposed to 1 of 2 possible changing climate cycles. In either case, the exposure to salt spray may be salt water spray or synthetic sea water prepared in accordance with the requirements of the test standard. The most appropriate test cycle and spray solutions are to be agreed between parties.
The first climate cycle comprises a continuous indirect spray of neutral (pH 6.5–7.2) salt water/synthetic seawater solution, which falls-out on to the specimens at a rate of 1–2 ml/80 cm 2 /hour. During this spraying, the chamber is dosed with SO 2 gas at a rate of 35 cm 3 /minute/m 3 of chamber volume, for 1 hour in every 6 hours of spraying. The entire test cycle is at a constant chamber temperature of 35 °C. The number of cycle repeats and therefore the test duration is variable.
The second climate cycle comprises 0.5 hours of continuous indirect spray of neutral (pH 6.5–7.2) salt water/synthetic seawater solution, which falls-out on to the specimens at a rate of 1–2 ml/80 cm 2 /hour. This is followed by 0.5 hours of dosing with SO 2 gas at a rate of 35 cm 3 /minute/m 3 of chamber volume. This is followed by 2 hours of high humidity soak. The entire test cycle is at a constant chamber temperature of 35 °C. The number of cycle repeats and therefore the test duration is variable. [ 2 ]
ASTM G85 Annex A5 – Dilute Electrolyte Salt Fog/Dry Test (cyclic)
This test can be used to test the relative resistance to corrosion of paints on steel when exposed to a changing climate of dilute salt spray at ambient temperature, followed by air drying at elevated temperature.
It is a popular test in the surface coatings industry, where it is also referred to as the PROHESION test.
Test specimens are placed in an enclosed chamber, and exposed to a changing climate with the following 2-part cycle.
First, a 1-hour exposure to a continuous indirect spray of salt water solution, prepared in accordance with the requirements of the test standard and acidified (pH 3.1–3.3) by the addition of acetic acid.
This spray is set to fall on the specimens at a rate of 1–2 ml/80 cm 2 /hour, in an ambient chamber temperature (21–27 °C). This is followed by a 1-hour exposure to an air drying (purge) climate at 35 °C.
The cycle repeats until the desired duration has been achieved. [ 2 ]
Chamber construction, testing procedure and testing parameters are standardized under national and international standards, such as ASTM B 117 and ISO 9227. These standards describe the necessary information to carry out this test; testing parameters such as temperature, air pressure of the sprayed solution, preparation of the spraying solution, concentration, pH , etc. Daily checking of testing parameters is necessary to show compliance with the standards, so records shall be maintained accordingly. ASTM B117 and ISO 9227 are widely used as reference standards. Testing cabinets are manufactured according to the specified requirements here.
However, these testing standards neither provide information of testing periods for the coatings to be evaluated, nor the appearance of corrosion products in form of salts. Requirements are agreed between customer and manufacturer. In the automotive industry requirements are specified under material specifications. Different coatings have different behavior in salt spray test and consequently, test duration will differ from one type of coating to another. For example, a typical electroplated zinc and yellow passivated steel part lasts 96 hours in salt spray test without white rust . Electroplated zinc-nickel steel parts can last more than 720 hours in NSS test without red rust (or 48 hours in CASS test without red rust) Requirements are established in test duration (hours) and coatings shall comply with minimum testing periods.
Artificial seawater which is sometimes used for Salt Spray Testing can be found at ASTM International . The standard for Artificial Seawater is ASTM D1141-98 which is the standard practice for the preparation of substitute ocean water.
Typical coatings that can be evaluated with this method are:
Hot-dip galvanized surfaces are not generally tested in a salt spray test (see ISO 1461 or ISO 10684). Hot-dip galvanizing produces zinc carbonates when exposed to a natural environment, thus protecting the coating metal and reducing the corrosion rate. The zinc carbonates are not produced when a hot-dip galvanized specimen is exposed to a salt spray fog, therefore this testing method does not give an accurate measurement of corrosion protection. ISO 9223 gives the guidelines for proper measurement of corrosion resistance for hot-dip galvanized specimens.
Painted surfaces with an underlying hot-dip galvanized coating can be tested according to this method. See ISO 12944-6.
Testing periods range from a few hours (e.g. 8 or 24 hours of phosphated steel) to more than a month (e.g. 720 hours of zinc-nickel coatings, 1000 hours of certain zinc flake coatings). | https://en.wikipedia.org/wiki/Salt_spray_test |
Salt tectonics , or halokinesis , or halotectonics , is concerned with the geometries and processes associated with the presence of significant thicknesses of evaporites containing rock salt within a stratigraphic sequence of rocks. This is due both to the low density of salt, which does not increase with burial, and its low strength. [ 1 ]
Salt structures (excluding undeformed layers of salt) have been found in more than 120 sedimentary basins around the world. [ 2 ]
Structures may form during continued sedimentary loading, without any external tectonic influence, due to gravitational instability. Pure halite has a density of 2160 kg/m 3 . When initially deposited, sediments generally have a lower density of 2000 kg/m 3 , but with loading and compaction their density increases to 2500 kg/m 3 , which is greater than that of salt. [ 3 ] Once the overlying layers have become denser, the weak salt layer will tend to deform into a characteristic series of ridges and depressions, due to a form of Rayleigh–Taylor instability . Further sedimentation will be concentrated in the depressions and the salt will continue to move away from them into the ridges. At a late stage, diapirs tend to initiate at the junctions between ridges, their growth fed by movement of salt along the ridge system, continuing until the salt supply is exhausted. During the later stages of this process the top of the diapir remains at or near the surface, with further burial being matched by diapir rise, and is sometimes referred to as downbuilding . The Schacht Asse II and Gorleben salt domes in Germany are an example of a purely passive salt structure. [ citation needed ]
Such structures do not always form when a salt layer is buried beneath a sedimentary overburden. This can be due to a relatively high strength overburden or to the presence of sedimentary layers interbedded within the salt unit that increase both its density and strength. [ citation needed ]
Active tectonics will increase the likelihood of salt structures developing. In the case of extensional tectonics , faulting will both reduce the strength of the overburden and thin it. [ 4 ] In an area affected by thrust tectonics , buckling of the overburden layer will allow the salt to rise into the cores of anticlines , as seen in salt domes in the Zagros Mountains and in El Gordo diapir (Coahuila fold-and-thrust belt, NE Mexico). [ 5 ]
If the pressure within the salt body becomes sufficiently high it may be able to push through its overburden, this is known as forceful diapirism. Many salt diapirs may contain elements of both active and passive salt movement. An active salt structure may pierce its overburden and from then on continue to develop as a purely passive salt diapir. [ citation needed ]
In those cases where salt layers do not have the conditions necessary to develop passive salt structures, the salt may still move into relatively low pressure areas around developing folds and faults. Such structures are described as reactive . [ citation needed ]
When one or more salt layers are present during extensional tectonics , a characteristic set of structures is formed. Extensional faults propagate up from the middle part of the crust until they encounter the salt layer. The weakness of the salt prevents the fault from propagating through. However, continuing displacement on the fault offsets the base of the salt and causes bending of the overburden layer. Eventually the stresses caused by this bending will be sufficient to fault the overburden. The types of structures developed depend on the initial salt thickness. In the case of a very thick salt layer there is no direct spatial relationship between the faulting beneath the salt and that in the overburden, such a system is said to be unlinked . For intermediate salt thicknesses, the overburden faults are spatially related to the deeper faults, but offset from them, normally into the footwall; these are known as soft-linked systems. When the salt layer becomes thin enough, the fault that develops in the overburden is closely aligned with that beneath the salt, and forms a continuous fault surface after only a relatively small displacement, forming a hard-linked fault. [ 6 ]
In areas of thrust tectonics salt layers act as preferred detachment planes. In the Zagros fold and thrust belt , variations in the thickness and therefore effectiveness of the late Neoproterozoic to Early Cambrian Hormuz salt are thought to have had a fundamental control on the overall topography. [ 7 ]
When a salt layer becomes too thin to be an effective detachment layer, due to salt movement, dissolution or removal by faulting, the overburden and the underlying sub-salt basement become effectively welded together. This may cause the development of new faults in the cover sequence and is an important consideration when modeling the migration of hydrocarbons .
Salt welds may also develop in the vertical direction by putting the sides of a former diapir in contact. [ 8 ]
Salt that pierces to the surface, either on land or beneath the sea, tends to spread laterally away and such salt is said to be "allochthonous". Salt glaciers are formed on land where this happens in an arid environment, such as in the Zagros Mountains. Offshore tongues of salt are generated that may join together with others from neighbouring piercements to form canopies. [ citation needed ]
On passive margins where salt is present, such as the Gulf of Mexico , salt tectonics largely control the evolution of deep-water sedimentary systems; for example submarine channels, as modern and ancient case studies show. [ 9 ]
A significant proportion of the world's hydrocarbon reserves are found in structures related to salt tectonics, including many in the Middle East , the South Atlantic passive margins ( Brazil , Gabon and Angola ), the Gulf of Mexico, [ citation needed ] and the Pricaspian Basin. [ 10 ] | https://en.wikipedia.org/wiki/Salt_tectonics |
Salt tide is a phenomenon in which the lower course of a river , with its low altitude with respect to the sea level , becomes salty when the discharge of the river is low during dry season, usually worsened by the result of astronomical high tide.
The lower course Xijiang ( West River ) in Guangdong , China was periodically affected and has been widely reported since 2004, for bringing shortage of fresh water supply to the western part of the Pearl River Delta . The salinity level of tap water at Zhuhai was reported to be as high as 800 mg per litre in late February 2006, more than 3 times higher than the World Health Organization standard of 250 mg.
This hydrology article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Salt_tide |
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