id int64 580 79M | url stringlengths 31 175 | text stringlengths 9 245k | source stringlengths 1 109 | categories stringclasses 160 values | token_count int64 3 51.8k |
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17,157,285 | https://en.wikipedia.org/wiki/Biocrystallization | Biocrystallization is the formation of crystals from organic macromolecules by living organisms. This may be a stress response, a normal part of metabolism such as processes that dispose of waste compounds, or a pathology. Template mediated crystallization is qualitatively different from in vitro crystallization. Inhibitors of biocrystallization are of interest in drug design efforts against lithiasis and against pathogens that feed on blood, since many of these organisms use this process to safely dispose of heme.
DNA
Under severe stress conditions the bacteria Escherichia coli protects its DNA from damage by sequestering it within a crystalline structure. This process is mediated by the stress response protein Dps and allows the bacteria to survive varied assaults such as oxidative stress, heat shock, ultraviolet light, gamma radiation and extremes of pH.
Heme
Blood feeding organisms digest hemoglobin and release high quantities of free toxic heme. To avoid destruction by this molecule, the parasite biocrystallizes heme to form hemozoin. To date, the only definitively characterized product of hematin disposal is the pigment hemozoin. Hemozoin is per definitionem not a mineral and therefore not formed by biomineralization. Heme biocrystallization has been found in blood feeding organisms of great medical importance including Plasmodium, Rhodnius and Schistosoma. Heme biocrystallization is inhibited by quinoline antimalarials such as chloroquine.
Targeting heme biocrystallization remains one of the most promising avenues for antimalarial drug development because the drug target is highly specific to the malarial parasite, and outside the genetic control of the parasite.
Lithiasis
Lithiasis (formation of stones) is a global human health problem. Stones can form in both urinary and gastrointestinal tracts. Related to the formation of stones is the formation of crystals; this can occur in joints (e.g. gout) and in the viscera.
See also
Biomineralization
Diatomaceous earth
Magnetotactic bacteria
Prion
References
External links
Order in stress – Lessons from the inanimate world
Metabolism
Cell biology
Chemical pathology
Biomineralization | Biocrystallization | Chemistry,Biology | 461 |
80,850 | https://en.wikipedia.org/wiki/XML-RPC | XML-RPC is a remote procedure call (RPC) protocol which uses XML to encode its calls and HTTP as a transport mechanism.
History
The XML-RPC protocol was created in 1998 by Dave Winer of UserLand Software and Microsoft, with Microsoft seeing the protocol as an essential part of scaling up its efforts in business-to-business e-commerce. As new functionality was introduced, the standard evolved into what is now SOAP.
UserLand supported XML-RPC from version 5.1 of its Frontier web content management system, released in June 1998.
XML-RPC's idea of a human-readable-and-writable, script-parsable standard for HTTP-based requests and responses has also been implemented in competing specifications such as Allaire's Web Distributed Data Exchange (WDDX) and webMethod's Web Interface Definition Language (WIDL). Prior art wrapping COM, CORBA, and Java RMI objects in XML syntax and transporting them via HTTP also existed in DataChannel's WebBroker technology.
The generic use of XML for remote procedure call (RPC) was patented by Phillip Merrick, Stewart Allen, and Joseph Lapp in April 2006, claiming benefit to a provisional application filed in March 1998. The patent was assigned to webMethods, located in Fairfax, Virginia. The patent expired on March 23, 2019.
Usage
In XML-RPC, a client performs an RPC by sending an HTTP request to a server that implements XML-RPC and receives the HTTP response. A call can have multiple parameters and one result. The protocol defines a few data types for the parameters and result. Some of these data types are complex, i.e. nested. For example, you can have a parameter that is an array of five integers.
The parameters/result structure and the set of data types are meant to mirror those used in common programming languages.
Identification of clients for authorization purposes can be achieved using popular HTTP security methods. Basic access authentication can be used for identification and authentication.
In comparison to RESTful protocols, where resource representations (documents) are transferred, XML-RPC is designed to call methods. The practical difference is just that XML-RPC is much more structured, which means common library code can be used to implement clients and servers and there is less design and documentation work for a specific application protocol. One salient technical difference between typical RESTful protocols and XML-RPC is that many RESTful protocols use the HTTP URI for parameter information, whereas with XML-RPC, the URI just identifies the server.
JSON-RPC is similar to XML-RPC.
Data types
Common datatypes are converted into their XML equivalents with example values shown below:
Examples
An example of a typical XML-RPC request would be:
<?xml version="1.0"?>
<methodCall>
<methodName>examples.getStateName</methodName>
<params>
<param>
<value><i4>40</i4></value>
</param>
</params>
</methodCall>
An example of a typical XML-RPC response would be:
<?xml version="1.0"?>
<methodResponse>
<params>
<param>
<value><string>South Dakota</string></value>
</param>
</params>
</methodResponse>
A typical XML-RPC fault would be:
<?xml version="1.0"?>
<methodResponse>
<fault>
<value>
<struct>
<member>
<name>faultCode</name>
<value><int>4</int></value>
</member>
<member>
<name>faultString</name>
<value><string>Too many parameters.</string></value>
</member>
</struct>
</value>
</fault>
</methodResponse>
Criticism
Recent critics (from 2010 and onwards) of XML-RPC argue that RPC calls can be made with plain XML, and that XML-RPC does not add any value over XML. Both XML-RPC and XML require an application-level data model, such as which field names are defined in the XML schema or the parameter names in XML-RPC. Furthermore, XML-RPC uses about 4 times the number of bytes compared to plain XML to encode the same objects, which is itself verbose compared to JSON.
See also
Weblogs.com
Pingback
Ajax (programming)
Component technologies
Comparison of data serialization formats
OPML
JSON-RPC
Web service
gRPC
References
External links
XML-based standards
Web services
Internet protocols
Remote procedure call | XML-RPC | Technology | 1,008 |
7,771,277 | https://en.wikipedia.org/wiki/Birkhoff%20polytope | The Birkhoff polytope Bn (also called the assignment polytope, the polytope of doubly stochastic matrices, or the perfect matching polytope of the complete bipartite graph ) is the convex polytope in RN (where N = n2) whose points are the doubly stochastic matrices, i.e., the matrices whose entries are non-negative real numbers and whose rows and columns each add up to 1. It is named after Garrett Birkhoff.
Properties
Vertices
The Birkhoff polytope has n! vertices, one for each permutation on n items. This follows from the Birkhoff–von Neumann theorem, which states that the extreme points of the Birkhoff polytope are the permutation matrices, and therefore that any doubly stochastic matrix may be represented as a convex combination of permutation matrices; this was stated in a 1946 paper by Garrett Birkhoff, but equivalent results in the languages of projective configurations and of regular bipartite graph matchings, respectively, were shown much earlier in 1894 in Ernst Steinitz's thesis and in 1916 by Dénes Kőnig. Because all of the vertex coordinates are zero or one, the Birkhoff polytope is an integral polytope.
Edges
The edges of the Birkhoff polytope correspond to pairs of permutations differing by a cycle:
such that is a cycle.
This implies that the graph of Bn is a Cayley graph of the symmetric group Sn. This also implies that the graph of B3 is a complete graph K6, and thus B3 is a neighborly polytope.
Facets
The Birkhoff polytope lies within an dimensional affine subspace of the n2-dimensional space of all matrices: this subspace is determined by the linear equality constraints that the sum of each row and of each column be one. Within this subspace, it is defined by n2 linear inequalities, one for each coordinate of the matrix, specifying that the coordinate be non-negative. Therefore, for , it has exactly n2 facets. For n = 2, there are two facets, given by a11 = a22 = 0, and a12 = a21 = 0.
Symmetries
The Birkhoff polytope Bn is both vertex-transitive and facet-transitive (i.e. the dual polytope is vertex-transitive). It is not regular for n>2.
Volume
An outstanding problem is to find the volume of the Birkhoff polytopes. This has been done for n ≤ 10. It is known to be equal to the volume of a polytope associated with standard Young tableaux. A combinatorial formula for all n was given in 2007. The following asymptotic formula was found by Rodney Canfield and Brendan McKay:
For small values the volume was estimated in 2014 while similar estimations follow.
Ehrhart polynomial
Determining the Ehrhart polynomial of a polytope is harder than determining its volume, since the volume can easily be computed from the leading coefficient of the Ehrhart polynomial. The Ehrhart polynomial associated with the Birkhoff polytope is only known for small values. It is conjectured that all the coefficients of the Ehrhart polynomials are non-negative.
Generalizations
The Birkhoff polytope is a special case of the transportation polytope, a polytope of nonnegative rectangular matrices with given row and column sums. The integer points in these polytopes are called contingency tables; they play an important role in Bayesian statistics.
The Birkhoff polytope is a special case of the matching polytope, defined as a convex hull of the perfect matchings in a finite graph. The description of facets in this generality was given by Jack Edmonds (1965), and is related to Edmonds's matching algorithm.
The Birkhoff polytope is a special case of the flow polytope of nonnegative flows through a network. It is related to the Ford–Fulkerson algorithm that computes the maximum flow in a flow network.
See also
Birkhoff algorithm
Permutohedron
Stable matching polytope
References
External links
Birkhoff polytope Web site by Dennis Pixton and Matthias Beck, with links to articles and volumes.
Polyhedral combinatorics
Matrices | Birkhoff polytope | Mathematics | 919 |
1,011,231 | https://en.wikipedia.org/wiki/Undercroft | An undercroft is traditionally a cellar or storage room, often brick-lined and vaulted, and used for storage in buildings since medieval times. In modern usage, an undercroft is generally a ground (street-level) area which is relatively open to the sides, but covered by the building above.
History
While some were used as simple storerooms, others were rented out as shops. For example, the undercroft rooms at Myres Castle in Fife, Scotland, of were used as the medieval kitchen and a range of stores. Many of these early medieval undercrofts were vaulted or groined, such as the vaulted chamber at Beverston Castle in Gloucestershire or the groined stores at Myres Castle. The term is sometimes used to describe a crypt beneath a church, used for burial purposes. For example, there is a 14th-century undercroft or crypt extant at Muchalls Castle in Aberdeenshire in Scotland, even though the original chapel above it was destroyed in an act of war in 1746.
Undercrofts were commonly built in England and Scotland throughout the thirteenth and early fourteenth centuries. They occur in cities such as London, Chester, Coventry and Southampton. The undercroft beneath the Houses of Parliament in London was rented to the conspirators behind the Gunpowder Plot.
Modern usage
In modern buildings, the term undercroft is often used to describe a ground-level parking area that occupies the footprint of the building (and sometimes extends to other service or garden areas around the structure). This type of parking is, however, discouraged by some urban design guidelines, as it prevents the ground floor from having activities (shops, restaurants or similar) that provide for a lively streetscape.
See also
The Undercroft, Guildford
The Undercroft, Southbank Centre – skateboarding and graffiti centre in London
Void deck
References
Rooms | Undercroft | Engineering | 367 |
4,131,678 | https://en.wikipedia.org/wiki/Hammond%27s%20postulate | Hammond's postulate (or alternatively the Hammond–Leffler postulate), is a hypothesis in physical organic chemistry which describes the geometric structure of the transition state in an organic chemical reaction. First proposed by George Hammond in 1955, the postulate states that:
If two states, as, for example, a transition state and an unstable intermediate, occur consecutively during a reaction process and have nearly the same energy content, their interconversion will involve only a small reorganization of the molecular structures.
Therefore, the geometric structure of a state can be predicted by comparing its energy to the species neighboring it along the reaction coordinate. For example, in an exothermic reaction the transition state is closer in energy to the reactants than to the products. Therefore, the transition state will be more geometrically similar to the reactants than to the products. In contrast, however, in an endothermic reaction the transition state is closer in energy to the products than to the reactants. So, according to Hammond’s postulate the structure of the transition state would resemble the products more than the reactants. This type of comparison is especially useful because most transition states cannot be characterized experimentally.
Hammond's postulate also helps to explain and rationalize the Bell–Evans–Polanyi principle. Namely, this principle describes the experimental observation that the rate of a reaction, and therefore its activation energy, is affected by the enthalpy of that reaction. Hammond's postulate explains this observation by describing how varying the enthalpy of a reaction would also change the structure of the transition state. In turn, this change in geometric structure would alter the energy of the transition state, and therefore the activation energy and reaction rate as well.
The postulate has also been used to predict the shape of reaction coordinate diagrams. For example, electrophilic aromatic substitution involves a distinct intermediate and two less well defined states. By measuring the effects of aromatic substituents and applying Hammond's postulate it was concluded that the rate-determining step involves formation of a transition state that should resemble the intermediate complex.
History
During the 1940s and 1950s, chemists had trouble explaining why even slight changes in the reactants caused significant differences in the rate and product distributions of a reaction. In 1955 George Hammond, a young professor at Iowa State University, postulated that transition-state theory could be used to qualitatively explain the observed structure-reactivity relationships. Notably, John E. Leffler of Florida State University proposed a similar idea in 1953. However, Hammond's version has received more attention since its qualitative nature was easier to understand and employ than Leffler's complex mathematical equations. Hammond's postulate is sometimes called the Hammond–Leffler postulate to give credit to both scientists.
Interpreting the postulate
Effectively, the postulate states that the structure of a transition state resembles that of the species nearest to it in free energy. This can be explained with reference to potential energy diagrams:
In case (a), which is an exothermic reaction, the energy of the transition state is closer in energy to that of the reactant than that of the intermediate or the product. Therefore, from the postulate, the structure of the transition state also more closely resembles that of the reactant. In case (b), the energy of the transition state is close to neither the reactant nor the product, making none of them a good structural model for the transition state. Further information would be needed in order to predict the structure or characteristics of the transition state. Case (c) depicts the potential diagram for an endothermic reaction, in which, according to the postulate, the transition state should more closely resemble that of the intermediate or the product.
Another significance of Hammond’s postulate is that it permits us to discuss the structure of the transition state in terms of the reactants, intermediates, or products. In the case where the transition state closely resembles the reactants, the transition state is called “early” while a “late” transition state is the one that closely resembles the intermediate or the product.
An example of the “early” transition state is chlorination. Chlorination favors the products because it is an exothermic reaction, which means that the products are lower in energy than the reactants. When looking at the adjacent diagram (representation of an "early" transition state), one must focus on the transition state, which is not able to be observed during an experiment. To understand what is meant by an “early” transition state, the Hammond postulate represents a curve that shows the kinetics of this reaction. Since the reactants are higher in energy, the transition state appears to be right after the reaction starts.
An example of the “late” transition state is bromination. Bromination favors the reactants because it is an endothermic reaction, which means that the reactants are lower in energy than the products. Since the transition state is hard to observe, the postulate of bromination helps to picture the “late” transition state (see the representation of the "late" transition state). Since the products are higher in energy, the transition state appears to be right before the reaction is complete.
One other useful interpretation of the postulate often found in textbooks of organic chemistry is the following:
Assume that the transition states for reactions involving unstable intermediates can be closely approximated by the intermediates themselves.
This interpretation ignores extremely exothermic and endothermic reactions which are relatively unusual and relates the transition state to the intermediates which are usually the most unstable.
Structure of transition states
SN1 reactions
Hammond's postulate can be used to examine the structure of the transition states of a SN1 reaction. In particular, the dissociation of the leaving group is the first transition state in a SN1 reaction. The stabilities of the carbocations formed by this dissociation are known to follow the trend tertiary > secondary > primary > methyl.
Therefore, since the tertiary carbocation is relatively stable and therefore close in energy to the R-X reactant, then the tertiary transition state will have a structure that is fairly similar to the R-X reactant. In terms of the graph of reaction coordinate versus energy, this is shown by the fact that the tertiary transition state is further to the left than the other transition states. In contrast, the energy of a methyl carbocation is very high, and therefore the structure of the transition state is more similar to the intermediate carbocation than to the R-X reactant. Accordingly, the methyl transition state is very far to the right.
SN2 reactions
Bimolecular nucleophilic substitution (SN2) reactions are concerted reactions where both the nucleophile and substrate are involved in the rate limiting step. Since this reaction is concerted, the reaction occurs in one step, where the bonds are broken, while new bonds are formed. Therefore, to interpret this reaction, it is important to look at the transition state, which resembles the concerted rate limiting step. In the "Depiction of SN2 Reaction" figure, the nucleophile forms a new bond to the carbon, while the halide (L) bond is broken.
E1 reactions
An E1 reaction consists of a unimolecular elimination, where the rate determining step of the mechanism depends on the removal of a single molecular species. This is a two-step mechanism. The more stable the carbocation intermediate is, the faster the reaction will proceed, favoring the products. Stabilization of the carbocation intermediate lowers the activation energy. The reactivity order is (CH3)3C- > (CH3)2CH- > CH3CH2- > CH3-.
Furthermore, studies describe a typical kinetic resolution process that starts out with two enantiomers that are energetically equivalent and, in the end, forms two energy-inequivalent intermediates, referred to as diastereomers. According to Hammond's postulate, the more stable diastereomer is formed faster.
E2 reactions
Elimination, bimolecular reactions are one step, concerted reaction where both base and substrate participate in the rate limiting step. In an E2 mechanism, a base takes a proton near the leaving group, forcing the electrons down to make a double bond, and forcing off the leaving group-all in one concerted step. The rate law depends on the first order concentration of two reactants, making it a 2nd order (bimolecular) elimination reaction. Factors that affect the rate determining step are stereochemistry, leaving groups, and base strength.
A theory, for an E2 reaction, by Joseph Bunnett suggests the lowest pass through the energy barrier between reactants and products is gained by an adjustment between the degrees of Cβ-H and Cα-X rupture at the transition state. The adjustment involves much breaking of the bond more easily broken, and a small amount of breaking of the bond which requires more energy. This conclusion by Bunnett is a contradiction from the Hammond postulate. The Hammond postulate is the opposite of what Bunnett theorized. In the transition state of a bond breaking step it involves little breaking when the bond is easily broken and much breaking when it is difficult to break. Despite these differences, the two postulates are not in conflict since they are concerned with different sorts of processes. Hammond focuses on reaction steps where one bond is made or broken, or the breaking of two or more bonds is done with no time taken occur simultaneously. The E2 theory transition state concerns a process when bond formation or breaking are not simultaneous.
Kinetics and the Bell–Evans–Polanyi principle
Technically, Hammond's postulate only describes the geometric structure of a chemical reaction. However, Hammond's postulate indirectly gives information about the rate, kinetics, and activation energy of reactions. Hence, it gives a theoretical basis for the understanding the Bell–Evans–Polanyi principle, which describes the experimental observation that the enthalpy and rate of a similar reactions were usually correlated.
The relationship between Hammond's postulate and the BEP principle can be understood by considering a SN1 reaction. Although two transition states occur during a SN1 reaction (dissociation of the leaving group and then attack by the nucleophile), the dissociation of the leaving group is almost always the rate-determining step. Hence, the activation energy and therefore rate of the reaction will depend only upon the dissociation step.
First, consider the reaction at secondary and tertiary carbons. As the BEP principle notes, experimentally SN1 reactions at tertiary carbons are faster than at secondary carbons. Therefore, by definition, the transition state for tertiary reactions will be at a lower energy than for secondary reactions. However, the BEP principle cannot justify why the energy is lower.
Using Hammond's postulate, the lower energy of the tertiary transition state means that its structure is relatively closer to its reactants R(tertiary)-X than to the carbocation product when compared to the secondary case. Thus, the tertiary transition state will be more geometrically similar to the R(tertiary)-X reactants than the secondary transition state is to its R(secondary)-X reactants. Hence, if the tertiary transition state is close in structure to the (low energy) reactants, then it will also be lower in energy because structure determines energy. Likewise, if the secondary transition state is more similar to the (high energy) carbocation product, then it will be higher in energy.
Applying the postulate
Hammond's postulate is useful for understanding the relationship between the rate of a reaction and the stability of the products.
While the rate of a reaction depends just on the activation energy (often represented in organic chemistry as ΔG‡ “delta G double dagger”), the final ratios of products in chemical equilibrium depends only on the standard free-energy change ΔG (“delta G”). The ratio of the final products at equilibrium corresponds directly with the stability of those products.
Hammond's postulate connects the rate of a reaction process with the structural features of those states that form part of it, by saying that the molecular reorganizations have to be small in those steps that involve two states that are very close in energy. This gave birth to the structural comparison between the starting materials, products, and the possible "stable intermediates" that led to the understanding that the most stable product is not always the one that is favored in a reaction process.
Explaining seemingly contradictory results
Hammond's postulate is especially important when looking at the rate-limiting step of a reaction. However, one must be cautious when examining a multistep reaction or one with the possibility of rearrangements during an intermediate stage. In some cases, the final products appear in skewed ratios in favor of a more unstable product (called the kinetic product) rather than the more stable product (the thermodynamic product). In this case one must examine the rate-limiting step and the intermediates. Often, the rate-limiting step is the initial formation of an unstable species such as a carbocation. Then, once the carbocation is formed, subsequent rearrangements can occur. In these kinds of reactions, especially when run at lower temperatures, the reactants simply react before the rearrangements necessary to form a more stable intermediate have time to occur. At higher temperatures when microscopic reversal is easier, the more stable thermodynamic product is favored because these intermediates have time to rearrange. Whether run at high or low temperatures, the mixture of the kinetic and thermodynamic products eventually reach the same ratio, one in favor of the more stable thermodynamic product, when given time to equilibrate due to microreversal.
See also
Bema Hapothle
Curtin–Hammett principle
Microscopic reversibility
Bell–Evans–Polanyi principle
References
Further reading
Chemical kinetics
Physical organic chemistry | Hammond's postulate | Chemistry | 2,904 |
70,721,697 | https://en.wikipedia.org/wiki/Neodymium%20tantalate | Neodymium tantalate is an inorganic compound with the chemical formula NdTaO4. It is prepared by reacting neodymium oxide and tantalum pentoxide at 1200 °C. It reacts with a mixture of tantalum pentoxide and chlorine gas at high temperature to obtain Nd2Ta2O7Cl2. It is ammonolyzed at high temperature to obtain oxynitrides of Nd-Ta.
Properties
Neodymium tantalate forms violet crystals of the monoclinic system, with space group I 2/a, cell parameters a = 0.55153 nm, b = 1.12388 nm, c = 0.51184 nm, β = 95.731°, Z = 4.
There is a metastable high-pressure phase of the monoclinic system, space group P 21/c, cell parameters a = 0.75920 nm, b = 0.54673 nm, c = 0.77022 nm, β = 100.032°, Z = 4.
Neodymium tantalate is insoluble in water.
See also
Neodymium
Tantalum
Tantalate
References
External links
Tantalates
Neodymium(III) compounds | Neodymium tantalate | Chemistry | 267 |
1,046,024 | https://en.wikipedia.org/wiki/Formal%20equivalence%20checking | Formal equivalence checking process is a part of electronic design automation (EDA), commonly used during the development of digital integrated circuits, to formally prove that two representations of a circuit design exhibit exactly the same behavior.
Equivalence checking and levels of abstraction
In general, there is a wide range of possible definitions of functional equivalence covering comparisons between different levels of abstraction and varying granularity of timing details.
The most common approach is to consider the problem of machine equivalence which defines two synchronous design specifications functionally equivalent if, clock by clock, they produce exactly the same sequence of output signals for any valid sequence of input signals.
Microprocessor designers use equivalence checking to compare the functions specified for the instruction set architecture (ISA) with a register transfer level (RTL) implementation, ensuring that any program executed on both models will cause an identical update of the main memory content. This is a more general problem.
A system design flow requires comparison between a transaction level model (TLM), e.g., written in SystemC and its corresponding RTL specification. Such a check is becoming of increasing interest in a system-on-a-chip (SoC) design environment.
Synchronous machine equivalence
The register transfer level (RTL) behavior of a digital chip is usually described with a hardware description language, such as Verilog or VHDL. This description is the golden reference model that describes in detail which operations will be executed during which clock cycle and by which pieces of hardware. Once the logic designers, by simulations and other verification methods, have verified register transfer description, the design is usually converted into a netlist by a logic synthesis tool. Equivalence is not to be confused with functional correctness, which must be determined by functional verification.
The initial netlist will usually undergo a number of transformations such as optimization, addition of Design For Test (DFT) structures, etc., before it is used as the basis for the placement of the logic elements into a physical layout. Contemporary physical design software will occasionally also make significant modifications (such as replacing logic elements with equivalent similar elements that have a higher or lower drive strength and/or area) to the netlist. Throughout every step of a very complex, multi-step procedure, the original functionality and the behavior described by the original code must be maintained. When the final tape-out is made of a digital chip, many different EDA programs and possibly some manual edits will have altered the netlist.
In theory, a logic synthesis tool guarantees that the first netlist is logically equivalent to the RTL source code. All the programs later in the process that make changes to the netlist also, in theory, ensure that these changes are logically equivalent to a previous version.
In practice, programs have bugs and it would be a major risk to assume that all steps from RTL through the final tape-out netlist have been performed without error. Also, in real life, it is common for designers to make manual changes to a netlist, commonly known as Engineering Change Orders, or ECOs, thereby introducing a major additional error factor. Therefore, instead of blindly assuming that no mistakes were made, a verification step is needed to check the logical equivalence of the final version of the netlist to the original description of the design (golden reference model).
Historically, one way to check the equivalence was to re-simulate, using the final netlist, the test cases that were developed for verifying the correctness of the RTL. This process is called gate level logic simulation. However, the problem with this is that the quality of the check is only as good as the quality of the test cases. Also, gate-level simulations are notoriously slow to execute, which is a major problem as the size of digital designs continues to grow exponentially.
An alternative way to solve this is to formally prove that the RTL code and the netlist synthesized from it have exactly the same behavior in all (relevant) cases. This process is called formal equivalence checking and is a problem that is studied under the broader area of formal verification.
A formal equivalence check can be performed between any two representations of a design: RTL <> netlist, netlist <> netlist or RTL <> RTL, though the latter is rare compared to the first two. Typically, a formal equivalence checking tool will also indicate with great precision at which point there exists a difference between two representations.
Methods
There are two basic technologies used for boolean reasoning in equivalence checking programs:
Binary decision diagrams, or BDDs: A specialized data structure designed to support reasoning about boolean functions. BDDs have become highly popular because of their efficiency and versatility.
Conjunctive Normal Form Satisfiability: SAT solvers returns an assignment to the variables of a propositional formula that satisfies it if such an assignment exists. Almost any boolean reasoning problem can be expressed as a SAT problem.
Commercial applications for equivalence checking
Major products in the Logic Equivalence Checking (LEC) area of EDA are:
FormalPro by Mentor Graphics
Questa SLEC by Mentor Graphics
Conformal by Cadence
Jasper by Cadence
Formality by Synopsys
VC Formal by Synopsys
360 EC by OneSpin Solutions
ATEC by ATEC
Generalizations
Equivalence Checking of Retimed Circuits: Sometimes it is helpful to move logic from one side of a register to another, and this complicates the checking problem.
Sequential Equivalence Checking: Sometimes, two machines are completely different at the combinational level, but should give the same outputs if given the same inputs. The classic example is two identical state machines with different encodings for the states. Since this cannot be reduced to a combinational problem, more general techniques are required.
Equivalence of Software Programs, i.e. checking if two well-defined programs that take N inputs and produce M outputs are equivalent: Conceptually, you can turn software into a state machine (that's what the combination of a compiler does, since a computer plus its memory form a very large state machine.) Then, in theory, various forms of property checking can ensure they produce the same output. This problem is even harder than sequential equivalence checking, since the outputs of the two programs may appear at different times; but it is possible, and researchers are working on it.
See also
Formal methods
References
Electronic Design Automation For Integrated Circuits Handbook, by Lavagno, Martin, and Scheffer, A survey of the field. This article was derived, with permission, from Volume 2, Chapter 4, Equivalence Checking, by Fabio Somenzi and Andreas Kuehlmann.
R.E. Bryant, Graph-based algorithms for Boolean function manipulation, IEEE Transactions on Computers., C-35, pp. 677–691, 1986. The original reference on BDDs.
Sequential equivalence checking for RTL models. Nikhil Sharma, Gagan Hasteer and Venkat Krishnaswamy. EE Times.
External links
CADP – provides equivalence checking tools for asynchronous designs
OneSpin 360 EC-FPGA – Functional correctness of FPGA synthesis from RTL code to final netlist
Electronic circuit verification
Formal methods | Formal equivalence checking | Engineering | 1,461 |
2,370,445 | https://en.wikipedia.org/wiki/Epsilon%20Ophiuchi | Epsilon Ophiuchi or ε Ophiuchi, formally named Yed Posterior (), is a red giant star in the constellation of Ophiuchus. Located less than five degrees south of the celestial equator in the eastern part of the constellation, it forms a naked eye optical double with Delta Ophiuchi (named Yed Prior). With an apparent visual magnitude of 3.220, the star can be seen with the naked eye from most of the Earth under suitably dark skies. Parallax measurements yield an estimated distance of from the Sun.
Nomenclature
ε Ophiuchi (Latinised to Epsilon Ophiuchi) is the star's Bayer designation.
It bore the traditional name Yed Posterior. Yed derives from the Arabic يد yad meaning "hand". Epsilon and Delta Ophiuchi comprise the left hand of Ophiuchus (the Serpent Bearer) that holds the head of the serpent (Serpens Caput). Epsilon is Yed Posterior as it follows Delta across the sky. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Yed Posterior for this star on 5 October 2016 and it is now so included in the List of IAU-approved Star Names.
Epsilon Ophiuchi was a member of the indigenous Arabic asterism al-Nasaq al-Yamānī, the "Southern Line" of al-Nasaqān the "Two Lines", along with Alpha Serpentis, Delta Serpentis, Epsilon Serpentis, Delta Ophiuchi, Zeta Ophiuchi and Gamma Ophiuchi.
In Chinese, (), meaning Right Wall of Heavenly Market Enclosure, refers to an asterism which represents eleven ancient states in China and which mark the right borderline of the enclosure, consisting of Delta Ophiuchi, Beta Herculis, Gamma Herculis, Kappa Herculis, Gamma Serpentis, Beta Serpentis, Alpha Serpentis, Delta Serpentis, Epsilon Serpentis, Epsilon Ophiuchi and Zeta Ophiuchi. Consequently, the Chinese name for Epsilon Ophiuchi itself is (, ), representing the state Chu (楚) (or Tsoo), together with Phi Capricorni (or 24 Capricorni in R.H.Allen's version) in the Twelve States (asterism).
Properties
Epsilon Ophiuchi has a stellar classification of G9.5 IIIb, with the luminosity class of III indicating that this is a giant star that has exhausted the hydrogen and evolved away from the main sequence. This red giant has nearly double the Sun's mass and has expanded to an estimated radius of over ten times the radius of the Sun, giving it a luminosity of about 54 times the Sun. It is about a billion years old.
Unusually for a class G giant, it is cyanogen-deficient and carbon-deficient. The outer envelope of this star displays solar-type oscillations with a period of 0.19 days, allowing the methods of asteroseismology to be applied. However, the models for this star have not been able to distinguish whether this star is generating energy by the thermonuclear fusion of hydrogen along a shell, or the fusion of helium at its core. Either model produces a good fit to the star's physical properties. The projected rotational velocity of the star is 5.7 km s−1, and the inclination of the rotation axis to the line of sight from the Earth lies in the range of 41–73°.
References
External links
G-type giants
Double stars
Ophiuchus
Ophiuchi, Epsilon
Durchmusterung objects
Ophiuchi, 02
146791
079882
6075
Yed Posterior | Epsilon Ophiuchi | Astronomy | 784 |
35,640,199 | https://en.wikipedia.org/wiki/Rayman%20Legends | Rayman Legends is a platform video game developed by Ubisoft Montpellier and published by Ubisoft. It is the fifth main title in the Rayman series and the direct sequel to the 2011 game Rayman Origins. The game was released for Microsoft Windows, PlayStation 3, Xbox 360, Wii U, and PlayStation Vita platforms in August and September 2013. PlayStation 4 and Xbox One versions were released in February 2014, with a Stadia version released in November 2021. A Nintendo Switch port, titled Rayman Legends Definitive Edition, was released in North America, Europe and Australia on September 12, 2017.
Rayman Legends was announced at Electronic Entertainment Expo (E3) 2012 for Wii U and was planned for release during the console's launch window. However, the game was delayed to February 2013 in order to put the finishing touches to the game, and due to the financial failure of ZombiU, the release was delayed again by six months and the game was made multi-platform.
Rayman Legends received critical acclaim upon release. Critics praised the game's visuals, level design, controls, soundtrack, overall gameplay, and the large amount of content. The game experienced slow sales on release, but sold over a million copies by 2014.
Gameplay
The game carries on the style of gameplay from Rayman Origins in which up to four players (depending on the format) simultaneously make their way through various levels. Lums can be collected by touching them, defeating enemies, or freeing captured Teensies. Collecting Teensies unlocks new worlds, which can be played in any order once they are available. Along with Rayman, Globox, and the Teensies returning as playable characters, players can now control the new female character Barbara the Barbarian Princess, her sister and their cousins, once they are rescued from certain stages.
In addition to the main playable characters, Murfy the greenbottle, who first appeared in Rayman 2: The Great Escape, appears as an assist character. Murfy can perform various actions such as cutting through ropes, activating mechanisms, grabbing hold of enemies and assisting in gathering Lums. These offer a range of levels in which co-operation is required to progress. In the Wii U, PlayStation Vita, and PlayStation 4 versions of the game, an additional player can control Murfy directly with touch controls, using the Wii U GamePad, the Vita's front touch screen, and the DualShock 4 touchpad respectively. In single-player mode, control will switch over to Murfy during certain sections whilst the computer controls the player's character. In the PlayStation 3, Xbox 360, Xbox One, and PC versions of the game, Murfy moves automatically and can be prompted to interact with certain objects with button controls. Other new features include sections where players can fire projectile fists at enemies and rhythm based levels set to covers of songs such as "Black Betty", "Eye of the Tiger", and "Woo-Hoo".
The game features over one hundred twenty levels, including forty remastered levels from the original Rayman Origins, which are unlocked by obtaining Lucky Tickets, which can also win additional Lums and Teensies. Some levels feature remixed 'Invaded' versions, which must be completed as quickly as possible. The game also offers daily and weekly challenge stages, in which players can compete with other players via leaderboards in challenges such as collecting a certain number of Lums in a short time or surviving the longest on a stage. More challenge stages can be accessed by raising the player's 'awesomeness' rating, which increases by collecting trophies earned by rescuing Teensies, collecting a high number of Lums in each level or by having a high leaderboard position at the end of a challenge. A local multiplayer football game, Kung Foot, is also featured, in which players use attacks to knock a football into the opponent's goal.
Plot
One century after the events of Origins have passed, Rayman, Globox, and the Teensies have been sound asleep after the adventure. During that time, the Bubble Dreamer's nightmares have gotten stronger and expanded with help from the Magician (who survived and split himself into 5 Dark Teensies) and captured Barbara and her fellow warrior princesses. Upon finding out, Murfy wakes up Rayman and co. and tells them what has happened before setting off to end the chaos. After beating each world's boss, Rayman and co. punch each Magician into space, where they each end up being used as instruments by imps for fun in a parody of A Trip to the Moon.
Development
The game was first leaked in an online marketing survey, which hinted that the upcoming "Rayman Origins 2" would include dragons, vampires, ghosts, the return of the Land of the Livid Dead and also someone dear to the Rayman series, in addition to returning features from its predecessor. Subsequently, Ubisoft registered the domain names "RaymanLegends.com" and "Rayman-Legends.com".
On 27 April 2012, the game's first trailer was leaked, revealing several details about it, including new playable characters, as well as the inclusion of online multiplayer. The end of the trailer also showcased Wii U exclusive features such as the use of NFC to make figures placed on the touchscreen appear on the game, as demonstrated with figures of Rabbids and Ezio from Assassin's Creed. Ubisoft later released a statement that confirmed its development, though stated it was "intended as a purely internal demonstrative video, and in no way represents the final game, the final console or their features."
The game was officially unveiled for the Wii U and demonstrated by Ubisoft at the Electronic Entertainment Expo 2012 trade show, Murfy appeared as a playable character in the demo. Though Ubisoft has only confirmed the game's release on the Wii U, Ubisoft senior game manager Michael Micholic stated that Ubisoft is considering PS3, Xbox 360 and PC versions of Rayman Legends as "we're looking at a lot of different launch options". A trailer released at Gamescom 2012 revealed it would be exclusive to the Wii U.
It was originally set to be released on 30 November 2012 (as a Wii U launch title). However, on 8 October 2012, it was reported to be delayed. On 13 December 2012, a demo of the game was released on the Wii U eShop. The official release date was revealed to be 26 February 2013, but was delayed further to September 2013 to allow for the title to have a simultaneous release on PlayStation 3 and Xbox 360. This delay upset fans since the developer had stated that the Wii U version was already finished. Fans started a petition for the game to be released on the original date on the Wii U, which had over 11,000 people signed onto it. To appease fans, Ubisoft said the Wii U would get another exclusive demo in the future, however this was just as negatively received. Developers that worked on the game have also expressed their distaste for the delay, while creator Michel Ancel was photographed with protesters campaigning for the release of the game.
In response to the delay, the development team announced that they will be releasing the game's Online Challenges mode for free via the Nintendo eShop, which released on 25 April 2013. This mode features daily challenges based on one of five scenarios, one of which is exclusive to Wii U, and features online leaderboards and ghost functionality. They also stated that with the extra development time, they would be adding new levels, enemies and more to the game. On 24 February 2013, it was revealed that Michel Ancel and the Montpellier team might leave Ubisoft over the controversy but Ubisoft denied any rumours. According to Yves Guillemot, Chairman and CEO of Ubisoft, ZombiUs poor sales performance led to the decision of making Rayman Legends a multiplatform game. Although the team considered using Xbox Smartglass to recreate the game's Wii U GamePad features on Xbox 360, the system was not responsive enough.
On 1 August 2013 it was announced that Wii U owners who downloaded the Rayman Legends Challenges App prior to 28 August 2013 receive an exclusive costume for Rayman. Pre-orders of certain versions of the game either come with bonus character Avelina, inspired by Aveline de Grandpré from Assassin's Creed III: Liberation, or bonus costumes for Rayman. On 7 August 2013, in a Nintendo Direct presentation, two new costumes were announced for the Wii U version: a Mario costume for Rayman, and a Luigi costume for Globox. On 23 August, the Rayman Legends Musical Beatbox App became available on the internet, iTunes, and Android devices. This app allows users to create their own songs from scratch, or by using Legendary Mode, which allows them to edit the game songs with 3 choices: Teensies in Trouble, 20000 Lums Under the Sea, and Fiesta de los Muertos. On 28 August 2013, Ubisoft announced on the Rayman Legends site that the European PlayStation Vita Version has been delayed to 12 September 2013 to apply the "final level of polish" players expect from a Rayman game.
The game features various improvements to the Ubi Art Framework engine used in Origins. These include a new dynamic lighting system, which lightens or silhouettes characters based on their environment, along with stealth sections that make use of light and shadow, and the seamless integration of 3D elements in 2D environments, made prominent in the game's 3D modelled bosses and monsters.
A smartphone game based on Legends' art style, Rayman Fiesta Run, was developed by Pastagames and released for iOS and Android devices on 7 November 2013. It is the sequel to the previous title, Rayman Jungle Run.
On the PS4 and Xbox One, Rayman Legends took advantage of the improved specifications. This means the game uses uncompressed textures and features reduced loading times between levels. Rayman's bonus costumes from the PS3 and Xbox 360 versions are also readily available in these versions.
A Nintendo Switch port co-developed by Pastagames (who would later collaborate with Ubisoft on Rayman Mini), nicknamed Definitive Edition, was released in September 2017.
In 2020, Ubisoft announced a Play Your Part, Play At Home campaign during the COVID-19 pandemic. As part of this campaign, PC users were able to redeem a free digital copy of Rayman Legends (among other games) via the Ubisoft website.
Reception
Critical response
Rayman Legends received "universal acclaim", according to the review aggregator Metacritic. Edge gave the game a 9/10 praising it by saying "One of the most jubilant, vividly imagined and open-hearted platformers to come along in a long time".
The PlayStation Vita version of the game received a total score of 33/40 by Famitsu.
GamesRadar gave the game a score of 4.5 out of 5 stars, praising the level variety and presentation, whilst criticizing the sometimes chaotic multiplayer and some of the touchscreen sections during solo play.
Tom McShea of GameSpot rated the game a 9.0/10 praising the game mechanics, the level design and the local co-op.
GameTrailers gave the game a score of 9.1/10, stating that the co-operative play on the Wii U GamePad "only serves to complement the game design".
Jose Otero of IGN rated the game a 9.5/10, praising the gameplay and the design of the levels, saying that "Naturally, Rayman starts out with simple running, jumping, and punching, but before you know it you’re sneaking past dozens of deadly traps, battling huge bosses, or playing through awesome challenge levels that look like '90s music videos. Every time I thought I found a personal favorite stage, the next one came along and replaced it", but criticized the absence of online co-op.
Danielle Riendeau of Polygon rated the game an 8.5/10 saying that it is "a beautifully designed gauntlet".
Thomas Whitehead of Nintendo Life gave the Wii U version an "excellent" 9/10, stating it is "close to perfection", but with "minor missteps". He criticized the game's short length but added that "Clearly aware of this, the developers made those hours utterly glorious".
During the 17th Annual D.I.C.E. Awards, the Academy of Interactive Arts & Sciences nominated Rayman Legends for "Family Game of the Year", "Outstanding Achievement in Art Direction", and "Outstanding Achievement in Original Music Composition".
Sales
Although Legends outsold Origins in its first week from international sales with the Wii U version selling the most copies, the game failed to meet sales expectations. As of November 2013, the game's sales were approaching one million units, according to Ubisoft. In early November 2014, Ubisoft reported that Rayman Legends was still selling well and contributing to the company's earnings. As of February 4, 2019, Rayman Legends has sold 4.48 million copies across all platforms, including the PS Vita and Nintendo Switch.
Notes
References
External links
2013 video games
Cooperative video games
Video games about dragons
Multiplayer and single-player video games
Nintendo Network games
Nintendo Switch games
Platformers
PlayStation 3 games
PlayStation 4 games
PlayStation Vita games
Video game sequels
Rayman
Side-scrolling video games
Video games about shapeshifting
Video games about size change
Video games about dreams
Video games developed in France
Video games directed by Michel Ancel
Video games scored by Christophe Héral
Wii U games
Wii U eShop games
Windows games
Xbox 360 games
Xbox One games
Asymmetrical multiplayer video games
Stadia games
Pastagames games | Rayman Legends | Physics | 2,807 |
24,032,607 | https://en.wikipedia.org/wiki/Running%20total | A running total or rolling total is the summation of a sequence of numbers which is updated each time a new number is added to the sequence, by adding the value of the new number to the previous running total. Another term for it is partial sum.
The purposes of a running total are twofold. First, it allows the total to be stated at any point in time without having to sum the entire sequence each time. Second, it can save having to record the sequence itself, if the particular numbers are not individually important.
Method
Consider the sequence (5, 8, 3, 2). What is the total of this sequence?
Answer: 5 + 8 + 3 + 2 = 18. This is arrived at by simple summation of the sequence.
Now we insert the number 6 at the end of the sequence to get (5, 8, 3, 2, 6). What is the total of that sequence?
Answer: 5 + 8 + 3 + 2 + 6 = 24. This is arrived at by simple summation of the sequence. But if we regarded 18 as the running total, we need only add 6 to 18 to get 24. So, 18 was, and 24 now is, the running total. In fact, we would not even need to know the sequence at all, but simply add 6 to 18 to get the new running total; as each new number is added, we get a new running total.
The same method will also work with subtraction, but in that case it is not strictly speaking a total (which implies summation) but a running difference; not to be confused with a delta. This is used, for example, when scoring the game of darts. Similarly one can multiply instead of add to get the running product.
Use
While this concept is very simple, it is extremely common in everyday use. For example, most cash registers display a running total of the purchases so far rung in. By the end of the transaction this will, of course, be the total of all the goods. Similarly, the machine may keep a running total of all transactions made, so that at any point in time the total can be checked against the amount in the till, even though the machine has no memory of past transactions.
Typically many games of all kinds use running totals for scoring; the actual values of past events in the sequence are not important, only the current score, that is to say, the running total.
The central processing unit of computers for many years had a component called the accumulator. This accumulator, essentially, kept a running total; that is, it "accumulated" the results of individual calculations. This term is largely obsolete with more modern computers. A betting accumulator is the running product of the outcomes of several bets in sequence.
See also
Running average
Prefix sum
References
External links
cumulative at Wiktionary, a related term
Operations on numbers | Running total | Mathematics | 591 |
43,956,835 | https://en.wikipedia.org/wiki/Binding%20neuron | A binding neuron (BN) is an abstract concept of processing of input impulses in a generic neuron based on their temporal coherence and the level of neuronal inhibition. Mathematically, the concept may be implemented by most neuronal models including the well-known leaky integrate-and-fire model. The BN concept originated in 1996 and 1998 papers by A. K. Vidybida,
Description of the concept
For a generic neuron the stimuli are excitatory impulses. Normally, more than single input impulse is necessary for exciting neuron up to the level when it fires and emits an output impulse.
Let the neuron receives input impulses at consecutive moments of time . In the BN concept the temporal coherence between input impulses is defined as follows
The high degree of temporal coherence between input impulses suggests that in external media all
impulses can be created by a single complex event. Correspondingly, if BN is stimulated by a highly coherent set of input impulses, it fires and emits an output impulse. In the BN terminology, BN binds the elementary events (input impulses) into a single event (output impulse). The binding happens if the input impulses are enough coherent in time, and does not happen if those impulses do not have required degree of coherence.
Inhibition in the BN concept (essentially, the slow somatic potassium inhibition) controls the degree of temporal coherence required for binding: the higher level of inhibition, the higher degree of temporal coherence is necessary for binding to occur.
The emitted output impulse is treated as abstract representation of the compound event (the set of coherent in time input impulses), see Scheme.
Origin
"Although a neuron requires energy, its main function is to receive signals and to send them out that is, to handle information." --- this words by Francis Crick point at the necessity to describe neuronal functioning in terms of processing of abstract signals
The two abstract concepts, namely, the "coincidence detector" and "temporal integrator" are offered in this course,
The first one expects that a neuron fires a spike if a number of input impulses are received at the same time. In the temporal integrator concept a neuron fires a spike after receiving a number of input impulses distributed in time.
Each of the two takes into account some features of real neurons since it is known that a realistic neuron can display
both coincidence detector and temporal integrator modes of activity depending on the stimulation applied,
.
At the same time, it is known that a neuron together with excitatory impulses receives also inhibitory stimulation.
A natural development of the two above mentioned concepts could be a concept which endows inhibition with its own signal processing role.
In the neuroscience, there is an idea of binding problem.
For example, during visual perception, such features as form, color and stereopsis are represented in the brain by
different neuronal assemblies. The mechanism ensuring those features to be perceived as belonging to a single real object is called "feature binding",
.
The experimentally approved opinion is that precise temporal coordination between neuronal impulses is required for the binding to occur,
This coordination mainly means that signals about different features must arrive to certain areas in the brain within a certain time window.
The BN concept reproduces at the level of single generic neuron the requirement, which is necessary for the feature binding to occur, and which was
formulated earlier at the level of large-scale neuronal assemblies.
Its formulation is made possible by the analysis of response of the
Hodgkin–Huxley model to stimuli similar to those the real neurons receive
in the natural conditions, see "Mathematical implementations", below.
Mathematical implementations
Hodgkin–Huxley (H-H) model
Hodgkin–Huxley model — physiologically substantiated neuronal model,
which operates in terms of
transmembrane ionic currents, and describes mechanism of generation of action potential.
In the paper
the response of the H-H model was studied numerically to stimuli composed of many
excitatory impulses distributed randomly within a time window :
Here denotes magnitude of
excitatory postsynaptic potential at moment ;
— is the moment of arrival of -th impulse; — is the total number of impulses the
stimulus is composed of. The numbers are random,
distributed uniformly within interval
. The stimulating current applied in the H-H equations
is as follows
where — is the capacity of unit area of excitable membrane.
The probability to generate action potential was calculated as a function
of the window width .
Different constant potassium conductances were added to the H-H equations
in order to create certain levels of
inhibitory potential. The dependencies obtained, if recalculated as functions of ,
which is analogous to temporal coherence of impulses in the compound stimulus, have step-like form.
The location of the step is controlled by the level of inhibition potential,
see Fig. 1.
Due to this type of dependence, the H-H equations can be treated as mathematical model of the BN concept.
Leaky integrate and fire neuron (LIF)
Leaky integrate and fire neuron is a widely used abstract neuronal model.
If to state a similar problem for the LIF neuron with appropriately chosen
inhibition mechanism,
then it is possible to obtain step-like dependencies similar to the Fig. 1
as well.
Therefore, the LIF neuron as well can be considered as mathematical model of the BN concept.
Binding neuron model
The binding neuron model implements the BN concept in the most refined form.
In this model each input impulse is stored in the neuron during fixed
time and then disappears.
This kind of memory serves as surrogate of the
excitatory postsynaptic potential.
The model has a threshold : if the number of stored in
the BN impulses exceeds
then the neuron fires a spike and clears it internal memory. The presence of
inhibition results in the decreased .
In the BN model, it is necessary to control the time to live of any stored
impulse during calculation of the neuron's
response to input stimulation. This makes the BN model more complicated
for numerical simulation than the LIF model.
On the other hand, any impulse spends finite time
in the BN model neuron. This is in contrast to the
LIF model, where traces of any impulse can be present infinitely long.
This property of the BN model allows to
get precise description of output activity of BN stimulated with random
stream of input impulses, see
.
The limiting case of BN with infinite memory, τ→∞, corresponds to
the temporal integrator.
The limiting case of BN with infinitely short memory, τ→0, corresponds
to the coincidence detector.
Integrated circuit implementation
The above-mentioned and other neuronal models and nets made of them can be implemented in microchips. Among different chips it is worth mentioning the field-programmable gate arrays. These chips can be used for implementation of any neuronal model, but the BN model can be programmed most naturally because it can use only integers and do not need solving differential equations. Those features are used, e.g. in and
Limitations
As an abstract concept the BN model is subjected to necessary limitations. Among those are such as ignoring neuronal morphology, identical magnitude of input impulses, replacement of a set of transients with different relaxation times, known for a real neuron, with a single time to live, , of impulse in neuron, the absence of refractoriness and fast (chlorine) inhibition. The BN model has the same limitations, yet some of them can be removed in a complicated model, see, e.g., where the BN model is used with refractoriness and fast inhibition.
References
Biophysics
Computational neuroscience | Binding neuron | Physics,Biology | 1,598 |
29,476,668 | https://en.wikipedia.org/wiki/Soil%20bioengineering | Soil and Water Bioengineering is a discipline of civil engineering. It pursues technological, ecological, economic as well as design goals and seeks to achieve these primarily by making use of living materials, i.e. seeds, plants, part of plants and plant communities, and employing them in near–natural constructions while exploiting the manifold abilities inherent in plants.
Soil bioengineering may sometimes be a substitute for classical engineering works; however, in most cases it is a meaningful and necessary method of complementing the latter.
Its application suggests itself in all fields of soil and hydraulic engineering, especially for slope and embankment stabilization and erosion control.
Soil bioengineering is the use of living plant materials to provide some engineering function. Soil bioengineering is an effective tool for treatment of a variety of unstable and / or eroding sites. Soil bioengineering techniques have been used for many centuries. More recently Schiechtl (1980) has encouraged the use of soil bioengineering with a variety of European examples. Soil bioengineering is now widely practiced throughout the world for the treatment of erosion and unstable slopes.
Fields of Application and Plants for Soil Bioengineering Control Works
Soil Bioengineering methods can be applied wherever the plants which are used as living building materials are able to grow well and develop.
This is the case in tropical, subtropical and temperate zones whereas there are obvious limits in dry and cold regions, i.e. where arid, semi–arid and frost zones prevail. In exceptional cases, lack of water may be compensated for by watering or irrigation.
In Europe, dry conditions limiting application exist in the Mediterranean as well as in some inner alpine and eastern European snowy regions. However, limits are most frequently imposed in alpine and arctic regions. These can usually be clearly noticed by the limited growth of woody plants (forest, tree and shrub lines) and the upper limits of closed turf cover. The more impoverished a region is in species, the less suited it is for the application of bioengineering methods.
Functions and Effects of Soil Bioengineering Structures
Technical functions
protection of soil surface from erosion by wind, precipitation, frost and flowing water
protection from rock fall
elimination or binding of destructive mechanical forces
reduction of flow velocity along banks
surface and/or deep soil cohesion and stabilization
drainage
protection from wind
aiding the deposition of snow, drift sand and sediments
increasing soil roughness and thus preventing avalanche release
Apart from these, ecological functions are gaining in importance, particularly as these can be fulfilled to a very limited extent only by classical engineering constructions.
Ecological functions
improvement of water regime by improved soil interception and storage capability as well as water
consumption by plants
soil drainage
protection from wind
protection from ambient air pollution
mechanical soil amelioration by the roots of plants
balancing of temperature conditions in near–ground layers of air and in the soil
shading
improvement of nutrient content in the soil and thus of soil fertility on previously raw soils
balancing of snow deposits
noise protection
yield increase on neighbouring cropland
Landscaping functions
healing of wounds inflicted on the landscape by disasters and humans (exploitation of mineral resources, construction work, deposition of overburden, tunnel excavation material, industrial and domestic waste)
integration of structures into the landscape
concealment of offending structures
enrichment of the landscape by creating new features and structures, shapes and colours of vegetation
Economic effects
Bioengineering control works are not always necessarily cheaper in construction when compared to classical engineering structures. However, when taking into account their lifetime including their service and maintenance, they will normally turn out to be more economical. Their special advantages are:
lower construction costs compared to “hard” constructions
lower maintenance and rehabilitation costs
creation of useful green areas and woody plant populations on previously derelict land
Useful for income generation
The result of soil bioengineering protection works are living systems which develop further and maintain their balance by natural succession (i.e. by dynamic self–control, without artificial input of energy). If the right living but also non–living building materials and the appropriate types of construction are chosen, exceptionally high sustainability requiring little maintenance effort can be achieved.
References
Soil science
Civil engineering
Forestry
Sustainable forest management
Forestry and the environment
Environmental soil science | Soil bioengineering | Engineering,Environmental_science | 844 |
56,056,679 | https://en.wikipedia.org/wiki/Methylenebis%28dibutyldithiocarbamate%29 | Methylenebis(dibutyldithiocarbamate) is the organosulfur compound with the formula CH2(SC(S)NBu2)2 (Bu = C4H9). It is a derivative of dibutyldithiocarbamate that is used as an additive to various lubricants, both as an antioxidant and to prevent metal surfaces. It is prepared by alkylation of the dithiocarbamate with dichloromethane. Although it is described as colored, simple esters of dithiocarbamate are typically colorless.
References
Dithiocarbamates
Oil additives | Methylenebis(dibutyldithiocarbamate) | Chemistry | 139 |
53,828,670 | https://en.wikipedia.org/wiki/Alkene%20carboamination | Alkene carboamination is the simultaneous formation of C–N and C–C bonds across an alkene. This method represents a powerful strategy to build molecular complexity with up to two stereocenters in a single operation. Generally, there are four categories of reaction modes for alkene carboamination. The first class is cyclization reactions, which will form a N-heterocycle as a result. The second class has been well established in the last decade. Alkene substrates with a tethered nitrogen nucleophile have been used in these transformations to promote intramolecular aminocyclization. While intermolecular carboamination is extremely hard, people have developed a strategy to combine the nitrogen and carbon part, which is known as the third class. The most general carboamination, which takes three individual parts and couples them together is still underdeveloped.
Reaction mechanisms
Different transition metals have been used to catalyze carboamination reactions, including palladium, copper, and rhodium etc. The reaction mechanism varies with different transition metals. For palladium-catalyzed carboamination reactions, Pd(0)/Pd(II) and Pd(II)/Pd(IV) catalytic cycles are the most common mechanisms that have been proposed.
The reaction mode for the key aminopalladation step is different in these two cases. In Wolfe’s chemistry, which is known as the Pd(0)/Pd(II) catalytic system, syn-aminopalladation is observed. While in the Pd(II)/Pd(IV) catalytic system, which was developed by Forrest Michael, anti-aminopalladation was observed. It is believed that the pH of the reaction will affect the existing form of the amine nucleophile, which will determine whether the nitrogen coordinates with palladium center or not during the aminopalladation step. For the C–H activation step in Pd(II)/Pd(IV) chemistry, since there is no directing effect on the aromatic ring, large excess of arenes are required.
In 2015, Rovis and coworkers reported a rhodium-catalyzed intermolecular carboamination. In this reaction, enoxyphthalimide was used to serve as both the nitrogen and carbon source. The reaction mechanism is proposed in the paper (vide infra).
In 2017, Liu and coworkers reported a copper-catalyzed three component carboamination reaction of styrenes. In the meantime, Engle and coworkers published a palladium-catalyzed three component carboamination reaction using directing group strategy. These two works are the very rare examples of three component carboamination reactions.
Applications
Carboamination is an efficient method to access nitrogen-containing molecules, especially N-heterocycles. (+)-Preussin, a pyrrolidine alkaloid, can be easily prepared via this methodology.
(−)-Tylophorine is another example, which can be synthesized using carboamination reaction.
References
Alkene complexes
Organic reactions | Alkene carboamination | Chemistry | 663 |
13,590,647 | https://en.wikipedia.org/wiki/Flunoxaprofen | Flunoxaprofen, also known as Priaxim, is a chiral nonsteroidal anti-inflammatory drug (NSAID). It is closely related to naproxen, which is also an NSAID. Flunoxaprofen has been shown to significantly improve the symptoms of osteoarthritis and rheumatoid arthritis. The clinical use of flunoxaprofen has ceased due to concerns of potential hepatotoxicity.
Structure
Flunoxaprofen is a two-ring heterocyclic compound derived from benzoxazole. It also contains a fluorine atom and a propanoyl group.
Synthesis
The overall synthesis is similar to that for benoxaprofen; in this case, para-fluorobenzoyl chloride is used when forming the benzoxazole ring..
A Sandmeyer reaction by diazotisation of 2-(4-aminophenyl)propanenitrile (1) followed by acid hydrolysis leads to the phenol (2), which is nitrated and reduced using stannous chloride or catalytic hydrogenation to give the aminophenol (4). Hydrolysis of the nitrile produces the carboxylic acid (5), which is converted to racemic flunoxaprofen by acylation with p-fluorobenzoyl chloride, followed by cyclisation.
Preparations
Because flunoxaprofen has limited water-solubility, additional steps must be taken in order to prepare syrups, creams, suppositories, etc. In order to make flunoxaprofen water-soluble, yet still active and efficient, it must be mixed with lysine and then suspended in an organic solvent that is soluble in water. A salt will crystallize upon cooling. The salt must then be filtered out and dried. Pharmacological testing of this now water-soluble compound has shown that it has anti-inflammatory properties equal to flunoxaprofen by itself.
Pharmacokinetics
The efficacy and safety of flunoxaprofen has been compared with those of naproxen in rheumatoid arthritis patients to show that the two drugs have equivalent therapeutical effects. Both drugs significantly relieve spontaneous pain which occurs both during the day and at night. Both drugs also significantly relieve the pain associated with active and passive motion and aid in relieving morning stiffness. The study also showed both drugs to be equally effective at improving grip strength.
Flunoxaprofen is administered as racemate. The absorption and disposition of both enantiomers were studied in 1988. No significant differences between stereoisomers were detected with respect to their absorption and elimination half-lives. However, further studies have shown that the S-enantiomer is the pharmacologically active form of the drug and does not undergo stereoinversion, while R-Flunoxaprofen is pharmacologically activated through biotransformation to the S-enantiomer. This stereospecific chiral inversion is mediated by the FLX-S-Acyl-CoA thioester. Pharmacokinetic studies with stereoselective bioassays have been carried out in different species after racemate dosage (and flunoxaprofen enantiomer derivatives have also been used as chiral fluorescent derivatizing agents to determine the enantiomers of other drug enantiomers in plasma).
It has been shown that the dextrorotatory form is particularly active and has a much higher therapeutic index than some other anti-inflammatories, including indomethacin and diclofenac. It has also been shown that flunoxaprofen inhibits leukotriene rather than prostaglandin synthesis. This is similar to benoxaprofen. Flunoxaprofen and benoxaprofen have been shown to have similar absorption characteristics. However, the distribution and elimination of flunoxaprofen has been shown to be much faster than benoxaprofen.
Adverse effects
A structural analog of flunoxaprofen is benoxaprofen. The two drugs are carboxylic acid analogs that form reactive acyl glucuronides. Benoxaprofen has been shown to be involved in rare hepatotoxicity. Because of this, benoxaprofen has been removed from the market. In response to this the clinical use of flunoxaprofen has also stopped, even though studies have shown that flunoxaprofen is less toxic than benoxaprofen.
The toxicity of these nonsteroidal anti-inflammatory drugs may be related to the covalent modification of proteins in response to the drugs' reactive acyl glucuronides. The reactivity of the acyl glucuronides appears to co-determine the extent of protein binding, as initially proposed by the research group of Benet et al. in 1993.
References
Carboxylic acids
Benzoxazoles
4-Fluorophenyl compounds | Flunoxaprofen | Chemistry | 1,061 |
9,465,520 | https://en.wikipedia.org/wiki/7-Dehydrositosterol | 7-Dehydrositosterol is a sterol which serves as a precursor for sitocalciferol (vitamin D5).
External links
Sterols
Vitamin D | 7-Dehydrositosterol | Chemistry,Biology | 39 |
1,649,915 | https://en.wikipedia.org/wiki/Unguent | An unguent is a soothing preparation spread on wounds, burns, rashes, abrasions or other topical injuries (i.e. damage to the skin). It is similar to an ointment, though typically an unguent is oilier and less viscous. It is usually delivered as a semi-solid paste spread on the skin, and it is often oily in order to suspend the medication or other active ingredients.
During the Victorian era, the use of the unguent macassar oil on the hair became so popular that antimacassars were invented to prevent damage to furniture.
Mercurochrome unguent
Various preparations of mercurochrome unguent are occasionally used as adjunct therapy in the treatment of furunculosis, and palliative relief of Kaposi sarcomas, although mercurials should only be used in extreme cases due to high toxicity and severe hypersensitivity or idiosyncratic reactions.
It was also used by the Egyptians to help soothe their skin from the dry heat.
See also
Aegyptiacum
Salve
Cream perfumes
Further reading
References
Routes of administration
Ointments | Unguent | Chemistry | 240 |
25,291,178 | https://en.wikipedia.org/wiki/Atom%20%28programming%20language%29 | Atom is a domain-specific language (DSL) in Haskell, for designing real-time embedded software.
History
Originally intended as a high-level hardware description language (HDL), Atom was created in early 2007 and released as free and open-source software (FOSS) of April of that year. Inspired by TRS and Bluespec, Atom compiled circuit descriptions, that were based on guarded atomic operations, or conditional term rewriting, into Verilog netlists for simulation and logic synthesis. As a hardware compiler, Atom's main objective is to maximize the number of operations, or rules, that can execute in a given clock cycle without violating the semantics of atomic operation. By employing the properties of conflict-free and sequentially composable rules, Atom reduced maximizing execution concurrency to a feedback arc set optimization of a rule-data dependency graph. This process was similar to James Hoe's original algorithm.
When Atom's author switched careers in late 2007, from logic design to embedded system software engineering, Atom was redesigned from an HDL to a domain-specific language targeting hard real-time computing embedded applications. As a result, Atom's compiler's main objective changed from maximizing rule concurrency to balancing processing load and minimizing worst case timing latency. In September 2008, Atom was presented at the Commercial Users of Functional Programming (CUFP) conference. In April 2009, in its new form, it was released as FOSS.
Overview
Atom is a concurrent programming language intended for embedded applications. Atom features compile time task scheduling and generates code with deterministic execution time and memory use, simplifying worst case execution time analysis for applications that need hard realtime performance. Atom's concurrency model is that of guarded atomic actions, which eliminates the need for, and the problems of using, mutex locks.
By removing runtime task scheduling and mutex locking, two services traditionally served by a real-time operating system (RTOS), Atom can eliminate the need and overhead of an RTOS in embedded applications.
Limits
To provide guarantees of deterministic execution time and memory consumption, Atom places several restrictions on computing. First, Atom designs are always finite state: all variables are global and declared at compile time and dynamic memory allocation is disallowed. Second, Atom provides no function or looping constructs. Instead, state variable updates are pure combinational logic functions of the current state.
References
External links
Declarative programming languages
Functional languages
Real-time computing
Synchronous programming languages
Statically typed programming languages
Haskell programming language family
Free software programmed in Haskell
Cross-platform free software
Free and open source compilers
Programming languages created in 2007
2007 software | Atom (programming language) | Technology | 554 |
32,345,601 | https://en.wikipedia.org/wiki/KIX%20domain | In biochemistry, the KIX domain (kinase-inducible domain (KID) interacting domain) or CREB binding domain is a protein domain of the eukaryotic transcriptional coactivators CBP and P300. It serves as a docking site for the formation of heterodimers between the coactivator and specific transcription factors. Structurally, the KIX domain is a globular domain consisting of three α-helices and two short 310-helices.
The KIX domain was originally discovered in 1996 as the specific and minimal region in CBP that binds and interacts with phosphorylated CREB to activate transcription. It was thus first termed CREB-binding domain. However, when it was later discovered that it also binds many other proteins, the more general name KIX domain became favoured. The KIX domain contains two separate binding sites: the "c-Myb site", named after the oncoprotein c-Myb, and the "MLL site", named after the proto-oncogene MLL (Mixed Lineage Leukemia, KMT2A).
The paralogous coactivators CBP (CREBBP) and P300 (EP300) are recruited to DNA-bound transcription factors to activate transcription. Coactivators can associate with promoters and enhancers in the DNA only indirectly through protein-protein contacts with transcription factors. CBP and P300 activate transcription synergistically in two ways: first, by remodelling and relaxing chromatin through their intrinsic histone acetyltransferase activity, and second, by recruiting the basal transcription machinery, such as RNA polymerase II.
The KIX domain belongs to the proposed GACKIX domain superfamily. GACKIX comprises structurally and functionally highly homologous domains in related proteins. It is named after the protein GAL11 / ARC105 (MED15), the plant protein CBP-like, and the KIX domain from CBP and P300. Additional instances include RECQL5 and related plant proteins. All of these contain a KIX domain or KIX-related domain that interacts with the transactivation domain of many different transcription factors. The distinction between a KIX domain, a KIX-related domain and a GACKIX domain is subject to an ongoing debate and not clearly defined.
The full CBP/P300 protein
Aside from the KIX domain, CBP and P300 contain many other protein binding domains that should not be confused (numbers are aa numberings):
CH1/TAZ1 domain, CBP[347–433], P300[323-423]
KIX domain, CBP[587–666], P300[566–645]
Bromodomain, CBP[1103–1175], P300[1067–1139]
CH2 domain (), CBP[1191–1317], P300[1155-1280].
HAT domain, CBP[1323–1700], P300[1287–1663]
CH3/ZZ domain, CBP[1701-1744], P300[1664-1707]
CH3/TAZ2 domain, CBP[1765–1846], P300[1728-1809]
IRF-3 binding (i-BiD), nuclear receptor coactivator binding (NCBD), or SRC1 interaction domain (SID; ), CBP[2020-2113], P300[1992-2098].
All three CH (cysteine/histidine-rich) domains are zinc fingers.
Interactions
Human and animal proteins:
Yeast proteins:
Viral proteins:
References
External links
KIXBASE, a database of KIX-superfamily domains and PDB structures (HMM training dataset)
Protein domains
Gene expression | KIX domain | Chemistry,Biology | 821 |
23,653,447 | https://en.wikipedia.org/wiki/C17H20N2O | {{DISPLAYTITLE:C17H20N2O}}
The molecular formula C17H20N2O (molar mass: 268.35 g/mol, exact mass: 268.1576 u) may refer to:
Centralite, or ethyl centralite
Michler's ketone
Remacemide
Molecular formulas | C17H20N2O | Physics,Chemistry | 73 |
49,986,238 | https://en.wikipedia.org/wiki/Caulobacter%20phage%20holin%20family | The Caulobacter Phage Holin (CauHol) Family (TC# 1.E.47) consists of several putative holins of 157 to 159 amino acyl residues (aas) in length that exhibit 2 transmembrane segments (TMSs). They derive from phage specific for Caulobacter species. These proteins are not functionally characterized. A representative list of proteins belonging to the CauHol family can be found in the Transporter Classification Database.
See also
Holin
Lysin
Transporter Classification Database
Further reading
Reddy, Bhaskara L.; Saier Jr., Milton H. (2013-11-01). "Topological and phylogenetic analyses of bacterial holin families and superfamilies". Biochimica et Biophysica Acta (BBA) - Biomembranes 1828 (11): 2654–2671.. . .
Saier, Milton H.; Reddy, Bhaskara L. (2015-01-01). "Holins in Bacteria, Eukaryotes, and Archaea: Multifunctional Xenologues with Potential Biotechnological and Biomedical Applications". Journal of Bacteriology 197(1): 7–17. . . . .
Wang, I. N.; Smith, D. L.; Young, R. (2000-01-01). "Holins: the protein clocks of bacteriophage infections". Annual Review of Microbiology 54: 799–825. . . .
Young, R.; Bläsi, U. (1995-08-01). "Holins: form and function in bacteriophage lysis". FEMS Microbiology Reviews 17 (1-2): 191–205. . .
References
Protein families
Membrane proteins
Transmembrane proteins
Transmembrane transporters
Transport proteins
Integral membrane proteins
Holins | Caulobacter phage holin family | Biology | 402 |
32,319,985 | https://en.wikipedia.org/wiki/Ichir%C5%8D%20Satake | (25 December 1927 – 10 October 2014) was a Japanese mathematician working on algebraic groups who introduced the Satake isomorphism and Satake diagrams. He was considered an iconic figure in the theory of linear algebraic groups and symmetric spaces.
Satake was born in Tokyo, Japan in 1927, and received his Ph.D. at the University of Tokyo in 1959 under the supervision of Shokichi Iyanaga. He was a professor at University of California, Berkeley from 1968 to 1983. After retirement he returned to Japan, where he spent time at Tohoku University and Chuo University. He died of respiratory failure on 10 October 2014.
Although they are often attributed to William Thurston, Satake was the first to introduce orbifold, which he did in the 1950s under the name of V-manifold. In , he gave the modern definition, along with the basic calculus of smooth functions and differential forms. He demonstrated that the de Rham theorem and Poincaré duality, along with their proofs, carry over to the orbifold setting. In , he demonstrated that the standard tensor calculus of bundles, connections, and curvature also carries over to orbifolds, along with the Chern-Gauss-Bonnet theorem and Shiing-Shen Chern's proof thereof.
Major publications
References
External links
FORMULA IN SIMPLE JORDAN ALGEBRAS ICHIRO SATAKE (Received May 7, 1984)
1927 births
2014 deaths
Deaths from respiratory failure
20th-century Japanese mathematicians
21st-century Japanese mathematicians
University of California, Berkeley faculty
University of Tokyo alumni
Academic staff of Tohoku University
Academic staff of Chuo University
University of Chicago faculty
Mathematicians from Tokyo
Group theorists
Topologists | Ichirō Satake | Mathematics | 338 |
57,876,996 | https://en.wikipedia.org/wiki/Binary%20angular%20measurement | Binary angular measurement (BAM) (and the binary angular measurement system, BAMS) is a measure of angles using binary numbers and fixed-point arithmetic, in which a full turn is represented by the value 1. The unit of angular measure used in those methods may be called binary radian (brad) or binary degree.
These representation of angles are often used in numerical control and digital signal processing applications, such as robotics, navigation, computer games, and digital sensors, taking advantage of the implicit modular reduction achieved by truncating binary numbers. It may also be used as the fractional part of a fixed-point number counting the number of full rotations of e.g. a vehicle's wheels or a leadscrew.
Representation
Unsigned fraction of turn
In this system, an angle is represented by an n-bit unsigned binary number in the sequence 0, ..., 2n−1 that is interpreted as a multiple of 1/2n of a full turn; that is, 360/2n degrees or 2π/2n radians. The number can also be interpreted as a fraction of a full turn between 0 (inclusive) and 1 (exclusive) represented in binary fixed-point format with a scaling factor of 1/2n. Multiplying that fraction by 360° or 2π gives the angle in degrees in the range 0 to 360, or in radians, in the range 0 to 2π, respectively.
For example, with n = 8, the binary integers (00000000)2 (fraction 0.00), (01000000)2 (0.25), (10000000)2 (0.50), and (11000000)2 (0.75) represent the angular measures 0°, 90°, 180°, and 270°, respectively.
The main advantage of this system is that the addition or subtraction of the integer numeric values with the n-bit arithmetic used in most computers produces results that are consistent with the geometry of angles. Namely, the integer result of the operation is automatically reduced modulo 2n, matching the fact that angles that differ by an integer number of full turns are equivalent. Thus one does not need to explicitly test or handle the wrap-around, as one must do when using other representations (such as number of degrees or radians in floating-point).
Signed fraction of turn
Alternatively, the same n bits can also be interpreted as a signed integer in the range −2n−1, ..., 2n−1−1 in the two's complement convention. They can also be interpreted as a fraction of a full turn between −0.5 (inclusive) and +0.5 (exclusive) in signed fixed-point format, with the same scaling factor; or a fraction of half-turn between −1.0 (inclusive) and +1.0 (exclusive) with scaling factor 1/2n−1.
Either way, these numbers can then be interpreted as angles between −180° (inclusive) and +180° (exclusive), with −0.25 meaning −90° and +0.25 meaning +90°. The result of adding or subtracting the numerical values will have the same sign as the result of adding or subtracting angles, once reduced to this range. This interpretation eliminates the need to reduce angles to the range when computing trigonometric functions.
Example
In the orbital data broadcast by the Global Positioning System, angles are encoded using binary angular measurement. In particular, each satellite broadcasts an ephemeris containing its six Keplerian orbital elements. Four of these are angles, which are encoded as 32-bit binary angles. In the lower-precision almanac data, 24-bit binary angles are used.
See also
Grade, 1/400 of a full turn
Binary scaling
CORDIC, algorithms for trigonometric functions
Constructible polygon, including all polygons with 2n sides
References
Units of plane angle
Binary arithmetic | Binary angular measurement | Mathematics | 818 |
38,068,881 | https://en.wikipedia.org/wiki/Native%20American%20ethnobotany | This is a list of plants used by the indigenous people of North America. For lists pertaining specifically to the Cherokee, Iroquois, Navajo, and Zuni, see Cherokee ethnobotany, Iroquois ethnobotany, Navajo ethnobotany, and Zuni ethnobotany.
A
Abronia fragrans (snowball-sand verbena) Used as both food and medicine. See article for complete list of uses.
Acer glabrum var. douglasii (Douglas maple), used by Plateau tribes as a treatment for diarrhea.
Acer glabrum var. glabrum The Blackfoot take an infusion of the bark in the morning as a cathartic. The Okanagan-Colville, when hunting, use a branch tied in a knot and placed over the bear's tracks while hunting to stop the wounded bear. The Thompson people use a decoction of wood and bark taken for nausea caused by smelling a corpse.
Acer negundo (box elder), used as food, lumber, and medicine. Please see article for full information.
Acer saccharinum (silver maple), an infusion of bark removed from the south side of the tree is used by the Mohegan for cough medicine. It is also used by other tribes for various purposes.
Acer saccharum (sugar maple), used by the Mohegan as a cough remedy, and the sap as a sweetening agent and to make maple syrup. It is also used by other tribes for various purposes.
Actaea racemosa (black cohosh), used to treat gynecological and other disorders, including sore throats, kidney problems, and depression.
Actaea rubra (red baneberry), used by the Algonquin for stomach pains, in some seasons for males, other seasons for females.
Agrimonia gryposepala, used by the Iroquois to treat diarrhea. Also used by the Cherokee to treat fever, by the Ojibwa for urinary problems, and by the Meskwaki and Prairie Potawatomi used it as a styptic for nosebleeds.
Allium tricoccum, used as both food and medicine. Please see the article for full information.
Alnus rhombifolia, used by some Plateau tribes for female health treatment.
Alnus rubra, used to treat poison oak, insect bites, and skin irritations. The Blackfoot Confederacy used an infusion made from the bark of red alder to treat lymphatic disorders and tuberculosis. Recent clinical studies have verified that red alder contains betulin and lupeol, compounds shown to be effective against a variety of tumors.
Artemisia californica (California Sagebrush), used by the Cahuilla and Tongva to alleviate menstrual cramps and menopause by taking it as a decoction, and consuming it regularly before the menstruation period. They also used it as an aid for child labor since the plant stimulates the uterine mucosa, quickening the process. The Cahuilla people chewed on the leaves, dried or fresh, to fight colds and coughs. The Ohlone used it to remove pain by applying it to wounds and teeth, to treat colds, coughs, and rheumatism by making it into a tea bath, and as a poultice for asthma.
Artemisia douglasiana, used to treat colds, fevers, and headaches.
Artemisia ludoviciana, used by several tribes for a variety of medicinal purposes.
Arundinaria, used for medicinal as well as many other purposes.
Asarum canadense, used to treat a number of ailments including dysentery, digestive problems, swollen breasts, coughs and colds, typhus, scarlet fever, nerves, sore throats, cramps, heaves, earaches, headaches, convulsions, asthma, tuberculosis, urinary disorders and venereal disease. They also used it as a stimulant, an appetite enhancer and a charm. It was also used as an admixture to strengthen other herbal preparations.
Asclepias verticillata, used medicinally.
B
Baccharis sarothroides, used by the Seri people to make a decoction by cooking the twigs. This tea is used to treat colds, sinus headache, and general sore achy ailments. The same tea is also used as a rub for sore muscles. Studies done on plant extracts show that desert broom is rich in leutolin, a flavonoid that has demonstrated anti-inflammatory, antioxidant, and cholesterol lowering capabilities. Desert broom also has quercetin, a proven antioxidant, and apigenin a chemical which binds to the same brain receptor sites that Valium does.
Balsamorhiza sagittata, used as food and medicine by many Native American groups, such as the Nez Perce, Kootenai, Cheyenne, and Salish.
Baptisia australis – the Cherokee would use the roots in teas as a purgative or to treat tooth aches and nausea, while the Osage made an eyewash with the plant.
Betula occidentalis, used by some Plateau tribes to treat pimples and sores.
Blephilia ciliata, traditionally used by the Cherokee to make a poultice to treat headaches.
Bloodroot, used as an emetic, respiratory aid, and other treatments.<ref>[http://herb.umd.umich.edu/herb/search.pl?searchstring=Sanguinaria+canadensis Native American Ethnobotany (University of Michigan - Dearborn: Sanguinaria canadensis']. accessed 2011-01-12.</ref>
C
Calypso (orchid), used by the Nlaka'pamux of British Columbia used it as a treatment for mild epilepsy.Cardamine diphylla, used for food and medicine. See article for full information.CaulophyllumCeanothus integerrimus, the branches of which were used among the Indigenous peoples of California in treating women after childbirth.Ceanothus velutinus, used by certain Plateau tribes to create herbal tea to induce sweating as a treatment for colds, fevers, and influenza. Leaves were also used when rinsing to help prevent dandruff. C. velutinus was known as "red root" by many Native American tribes due to the color of the inner root bark, and was used as a medicine for treating lymphatic disorders, ovarian cysts, fibroid tumors, and tonsillitis. Clinical studies of the alkaloid compounds in C. velutinus has verified its effectiveness in treating high blood pressure and lymphatic blockages.Chimaphila umbellata, used by some Plateau tribes in an herbal tea to treat tuberculosis.Claytonia virginica (Virginia spring-beauty), used medicinally by the Iroquois, who would give a cold infusion or decoction of the powdered roots to children suffering from convulsions. They would also eat the raw roots, believing that they permanently prevented conception. They would also eat the roots, as would the Algonquin people, who cooked them like potatoes.Cleome serrulata, used by tribes in the southwest to make an infusion to treat stomach illnesses and fevers. Poultices can be used on the eyes.Commelina dianthifolia, infusion of plant used by Keres as a strengthener for weakened tuberculosis patients.Cornus sericea, used by Plateau tribes to treat colds by eating the berries. Also used to slow bleeding.Moerman, Daniel E. (1998) "Cornus sericea ssp. occidentallis" Native American ethnobotany Timber Press, Portland, Oregon, page 178,
D
Datura wrightii, the plant, often the root but any part of the plant could be used, was made into a tea which was then consumed as a rite of passage in Chumash ceremonies due to being a deliriant hallucinogen.Delphinium nudicaule, the root of which was used as a narcotic by the Mendocino.
Devil's club, traditionally used by Native Americans to treat adult-onset diabetes and a variety of tumors. In vitro studies showed that extracts of devil's club inhibit tuberculosis microbes. The plant is used medicinally and ceremonially by the Tlingit people of Southeast Alaska, who refer to it as "Tlingit aspirin". A piece of devil's club hung over a doorway is said to ward off evil. The plant is harvested and used in a variety of ways, including lip balms, ointments, and herbal teas. Some Tlingit disapprove of the commercialization of the plant as they see it as a violation of its sacred status.
EEchinacea, Echinacea angustifolia was widely used by the North American Plains Indians for its general medicinal qualities. Echinacea was one of the basic antimicrobial herbs of eclectic medicine from the mid 19th century through the early 20th century, and its use was documented for snakebite, anthrax, and for relief of pain. In the 1930s echinacea became popular in both Europe and America as an herbal medicine. According to Wallace Sampson, MD, its modern-day use as a treatment for the common cold began when a Swiss herbal supplement maker was "erroneously told" that echinacea was used for cold prevention by Native American tribes who lived in the area of South Dakota. Although Native American tribes didn't use echinacea to prevent the common cold, some Plains tribes did use echinacea to treat some of the symptoms that could be caused by the common cold: The Kiowa used it for coughs and sore throats, the Cheyenne for sore throats, the Pawnee for headaches, and many tribes including the Lakotah used it as an analgesic. Native Americans learned of E. angustifolia by observing elk seeking out the plants and consuming them when sick or wounded, and identified those plants as elk root. The following table examines why various tribes use echinacea.
The entire echinacea plant is used medicinally, both dried and fresh. Common preparations include making a decoction or infusion of the roots and leaves, making a poultice of parts of the plant, juicing the root or simply using the leaves as they were.
Echinacea contains essential oils and polysaccharides that boost the immune system, leading to a faster recovery from various illnesses. Due to this property, echinacea has been commercialized and has had clinical trials support that it reduces the duration of a cold by 1–4 days and reduces the chance of developing a cold by 58%.Encelia farinosa (brittlebush), used by the Seri to treat toothache. For toothache the bark is removed, the branch heated in ashes, and then placed in the mouth to "harden" a loose tooth. The Cahuilla of California also used this as a toothache reliever, and to treat chest pain as well by heating the plant gum and applying it to the chest.Ephedra californica, used by the indigenous peoples of California.Epigaea repens, see article for full information.Equisetum hyemale, used by some Plateau tribes. They boiled the stalks to produce a drink used as a diuretic and to treat venereal disease.Erigenia bulbosa, the Cherokee were known to chew this plant as medicine for toothaches, it is unknown what parts of plant they chewed.Eriodictyon crassifolium, used by the Chumash people to keep airways open for proper breathing.Eriodictyon trichocalyx (Yerba Santa), used by the Cahuilla to pure blood and to treat coughs, colds, sore throats, asthma, tuberculosis, and catarrh. It was also used as a liniment, a poultice, and a tea bath to treating rheumatism, fatigued limbs, sores, and fevers. The Chumash also used this as a liniment for the feet and chest.Eriodictyon californicum (Yerba Santa), Native Americans used it to treat asthma, upper respiratory infections, and allergic rhinitis. The Chumash used it to poultice broken bones, wounds, insect bites, and sores. A steam bath was used to treat hemorrhoids.Eryngium aquaticum, used by the Cherokee for nausea, by the Choctaw people used it as a remedy for snakebite and gonorrhea, and by the Delaware people for intestinal worms.Erythrina herbacea, Creek women used an infusion of the root for bowel pain; the Choctaw used a decoction of the leaves as a general tonic; the Seminole used an extract of the roots for digestive problems, and extracts of the seeds, or of the inner bark, as an external rub for rheumatic disorders.Eurybia macrophylla (bigleaf aster), used as both food and medicine. Please see article for more information.
GGaultheria hispidula (creeping snowberry) Infusion of leaves used as a tonic for overeating by the Algonquin people. Fruit used as food. Used as a sedative by the Anticosti. Decoction of leaves or whole plant taken for unspecified purpose by Micmac. Leaves used by Ojibwa people to make a beverage.Gaultheria procumbens, used by various tribes.Gentiana villosa, Catawba Indians used the boiled roots as medicine to relieve back pain.Geranium maculatum, used by the Meskwaki people to brew a root tea for toothache and for painful nerves. They also mashed the roots for treating hemorrhoids.
Goldenseal, referred to by Prof. Benjamin Smith Barton in his first edition of Collections for an Essay Toward a Materia Medica of the United States (1798), as being used by the Cherokee as a cancer treatment.Gutierrezia microcephala, used by the Native Americans for various reasons. The Cahuilla used an infusion of the plant as a gargle or placed the plant in their mouths as a toothache remedy. The Hopi and Tewa both used the plant as a carminative, as prayer stick decorations, and for roasting sweet corn.
HHamamelis virginiana, also known as Witch Hazel. Native Americans produced witch hazel extract by boiling the stems of the shrub and producing a decoction, which was used to treat swellings, inflammations, and tumors. Early Puritan settlers in New England adopted this remedy from the natives, and its use became widely established in the United States. It is a flowering plant with multiple species native to North America. It has been widely used by Native Americans for its medicinal benefits, leading white settlers to incorporate it into their own medical practices. An extract of witch hazel stems is used to treat sore muscles, skin and eye inflammation and to stop bleeding. Witch hazel is utilized by many tribes, including the Menominee for sore legs of tribesmen who participate in sporting games, the Osage for skin ulcers and sores, the Potawatomi in sweat lodges for sore muscles and the Iroquois in tea for coughs and colds.
Witch hazel works as an astringent, a substance that causes the constriction of body tissues. The tannins and flavonoids found in witch hazel have astringent and antioxidant properties, respectively, which are thought to contract and protect blood vessels, thereby reducing inflammation. However, modern witch hazel extracts are often distilled and do not contain tannins due to health concerns.Heracleum maximum, used by various Native American peoples. Perhaps the most common use was to make poultices to be applied to bruises or sores.an infusion of the flowers can be rubbed on the body to repel flies and mosquitoes.Holodiscus discolor, used by Indian tribes, such as the Stl'atl'imx. They would steep the berries in boiling water to use as a treatment for diarrhea, smallpox, chickenpox and as a blood tonic.Holodiscus dumosus, used by the Paiute and Shoshone as medicine for problems such as stomachaches and colds.Hydrangea arborescens, used in the treatment of kidney and bladder stones.Hydrangea cinerea, used by the Cherokee.
IIlex verticillata, used by Native Americans for medicinal purposes, the origin of the name "fever bush".Iris missouriensis, the roots of which were used by some Plateau tribes to treat toothache.
JJeffersonia diphylla – the Cherokee reportedly used an infusion of this plant for treating dropsy and urinary tract problems, it was also used as a poultice for sores and inflammation. The Iroquois used a decoction of the plant to treat liver problems and diarrhea.Juniperus communis – Western American tribes combined the berries of Juniperus communis with Berberis root bark in a herbal tea. Native Americans also used juniper berries as a female contraceptive.Juniperus scopulorum, the leaves and inner bark of which were boiled by some Plateau tribes to create an infusion to treat coughs and fevers. The berries were also sometimes boiled into a drink used as a laxative and to treat colds.
KKrascheninnikovia lanata, used for a wide variety of ailments.
LLarrea tridentata, used by Native Americans in the Southwest as a treatment for many maladies, including sexually transmitted diseases, tuberculosis, chicken pox, dysmenorrhea, and snakebite. The shrub is still widely used as a medicine in Mexico. It contains nordihydroguaiaretic acid.Lobelia, used to treat respiratory and muscle disorders, and as a purgative. The species used most commonly in modern herbalism is Lobelia inflata (Indian tobacco).Lophophora williamsii, has at least 5,500 years of entheogenic and medicinal use by indigenous North Americans.
MMahonia aquifolium, used by some Plateau tribes to treat dyspepsia.Mahonia nervosa, an infusion of the root of which was used some Plateau tribes to treat rheumatism.Mahonia repens, used by the Tolowa and Karok of Northwest California used the roots for a blood and cough tonic, as well as by other tribes for various purposes.Malosma, the root bark of which was used by the Chumash to make an herbal tea for treating dysentery.Menispermum canadense, Cherokee used as a laxative, and as a gynecological and venereal aid. The root was used for skin diseases. The Lenape used it in a salve for sores on the skin.
OOsmunda claytoniana, used by the Iroquois for blood and venereal diseases and conditions.
PPectis papposa, used as food and medicine.Persicaria amphibia, used medicinally.Pinus quadrifolia, used medicinally by the Cahuilla by taking the resin and making a face cream usually used by girls to prevent sunburn. The resin was also used as a glue for fixing pottery and reattaching arrowheads to the arrow shafts. The nuts were given to babies as an alternative for breast milk; were ground then mixed with water as a drink; were roasted; were ground into mush; and were an important trade item. The pine needles and roots were materials for basketry and the bark was used as roofing material of houses. The wood was burnt as firewood because of high combustibility and incense for the pleasant smell it emitted when burnt. The Diegueno also ate nuts and the seeds also.Pinus strobus, the resin of which was used by the Chippewa to treat infections and gangrene.Fernald, M., A. Kinsey, and R. Rollins. 1943. Edible Wild Plants. Harper & Row, NY.Pluchea sericea, used as an antidiarrheal and eyewash.Podophyllum peltatum, used as an emetic, cathartic, and anthelmintic agent. They also boiled the poisonous root, and used the water to treat stomach aches.Populus tremuloides, the bark of which contains a substance that can be extracted and used as a quinine substitute.Prunus emarginata, used by Kwakwaka'wakw and other tribes for medicinal purposes, such as poultices and bark infusions.Prunus virginiana, the root bark of which was once made into an asperous-textured concoction used to ward off or treat colds, fever and stomach maladies by Native Americans.
Pseudognaphalium obtusifolium, ssp obtusifolium, see article for full information.
RRibes aureum, used as medicine by several tribes.Ribes divaricatum, used by various tribes in the Pacific Northwest.Ribes glandulosum (skunk currant), used in a compound decoction of the root for back pain and for "female weakness" by the Ojibwa people. The Cree people use a decoction of the stem, either by itself or mixed with wild red raspberry, to prevent clotting after birth. The Algonquin people use the berries as food.Ribes laxiflorum, used an infusion to make an eyewash (roots and or branches, by the Bella Coolah). Decoctions of: bark to remedy tuberculosis (with the roots, by the Skokomish); or for the common cold (Skagit): leaves and twigs, as a general tonic (Lummi).Ribes oxyacanthoides, used medicinally.
S
Sage is a small evergreen shrub used to treat inflammation, bacterial or viral infection and chronic illness. Commonly treated conditions include abdominal cramping/pain, bloating, bleeding, bruising, skin disease, cough, excessive sweating, menstrual cramps and flu as well as depression, obesity heart disease and cancer. Sage can be administered in tea, food, as a poultice or in smoke. Sage contains multiple essential oils as well as tannins and flavonoids, which have "carminative, antispasmodic, antiseptic, and astringent properties". In addition to being used in modern food preparation, sage is still utilized for herbal and pharmaceutical medicines with strong evidence supporting its impacts. The following table examines why various tribes use sage.Salvia apiana, several tribes used the seed for removing foreign objects from the eye, similar to the way that Clary sage seeds were used in Europe. A tea from the roots was used by the Cahuilla women for healing and strength after childbirth. The leaves are also burnt by many Native American tribes, with the smoke used in different purification rituals. A study performed at the University of Arizona in 1991 demonstrated that Salvia apiana has potential antibacterial properties against Staphylococcus aureus, Bacillus subtilis, Klebsiella pneumoniae, and Candida brassicae.Salvia mellifera, the leaves and stems of the plant were made by the Chumash into a strong sun tea. This was rubbed on the painful area or used to soak one's feet. The plant contains diterpenoids, such as aethiopinone and ursolic acid, that are pain relievers.Senegalia greggii, the fresh pods were eaten unripe by the Chemehuevi, Pima, and the Cahuilla. The Cahuilla dried the pods then ground it for mush and cakes, the Havasupai ground it to make bread flour, and the Seri ground it to meal to mix with water and sea lion oil for porridge. The Diegueno used it as food for domesticated animals. The Cahuilla and Pima used it for construction material and firewood. The Havasupai split the twigs to make as basket material and used bundles as a broom for dusting off metates. The Papago broke the twigs in half to make baskets, and were curved to make difficult weaves in the baskets. The Pima piled dried bushes for a brush fence, and used the branches for cradle frames too. The Papago deer hunters wore the branches as a disguise as a deer, and the buds and blossoms were dried for perfume pouches. The branches were used to dislodge saguaro fruits from the body, and the rods were used to remove flesh from animal skins. The Pima used the wood for bows.Silene latifolia, subspecies alba: Infusion used by the Ojibwa as a physic. Note that this plant is not native to the Americas and was introduced by Europeans.
T
Tobacco, previously used for a variety of medicinal purposesTrichostema lanatum, used for a variety of medicinal purposes.Trichostema lanceolatum, used by natives of northern California as a cold and fever remedy, a pain reliever, and a flea repellent.Triodanis perfoliata, see article for full information.
U
Poultices of Umbellularia leaves were used to treat rheumatism and neuralgias. A tea was made from the leaves to treat stomach aches, colds, sore throats, and to clear up mucus in the lungs. The leaves were steeped in hot water to make an infusion that was used to wash sores. The Pomo and Yuki tribes of Mendocino County treated headaches by placing a single leaf in the nostril or bathing the head with a laurel leaf infusion.
VViburnum prunifolium, a decoction of which was to treat gynecological conditions, including menstrual cramps, aiding recovery after childbirth, and in treating the effects of menopause.
Virginia iris – Cherokee and other tribes in the southeastern United States are known to have used Virginia iris for its medicinal properties. The root was pounded into a paste that was used as a salve for skin. An infusion made from the root was used to treat ailments of the liver, and a decoction of root was used to treat "yellowish urine". Virginia iris may have been one of the iris species used by the Seminole to treat "shock following alligator-bite".
W
The inner bark of willow trees has been used by Native American groups for health issues including headache, bleeding cuts, skin sores, fever, cough and hoarseness, menstrual cramping, stomach pain and diarrhea. The inner bark is most often made into tea and drank, though it is also made into a poultice to cover the skin over broken bones or used to wash skin and hair to promote skin repair and hair growth.
Willow bark contains salicin, a compound similar to aspirin that has anti-inflammatory, antipyretic, and analgesic properties. The following table examines why various tribes use willow.
One reason for the vast differences in the use of the willow is that there are many ways to prepare it and these different preparations allow for it to be utilized in different ways. For example, the Thompson people would make a concoction of wood, willow, soapberry branches and "anything weeds" to treat broken bones. If they wanted to treat a cold, however, the Thompson people would make a decoction of red willow branches and wild rose roots.
YYucca glauca'', used by the Blackfoot, Cheyenne, Lakota, and other tribes.
References
External links
http://herb.umd.umich.edu Native American Ethnobotany Database.
https://mc.miamioh.edu/mahkihkiwa/ Myaamia Ethnobotanical Database
See also
Navajo ethnobotany
Zuni ethnobotany
List of plants used in herbalism
Traditional Alaska Native medicine
Traditional knowledge
Ethnobotany
Ethnobotany
Ethnobotany
Ethnobotany
Lists of plants
Medical lists
Medicinal plants
Flora of the United States
Native American ethnobotany | Native American ethnobotany | Biology | 6,023 |
28,000,935 | https://en.wikipedia.org/wiki/Intubation | Intubation (sometimes entubation) is a medical procedure involving the insertion of a tube into the body. Patients are generally anesthetized beforehand. Examples include tracheal intubation, and the balloon tamponade with a Sengstaken–Blakemore tube (a tube into the gastrointestinal tract).
See also
Catheterization
Nasogastric intubation
Tracheal intubation
ROTIGS
References
Airway management
Emergency medical procedures
Medical equipment
Routes of administration | Intubation | Chemistry,Biology | 104 |
602,456 | https://en.wikipedia.org/wiki/Gardening%20%28cryptanalysis%29 | In cryptanalysis, gardening is the act of encouraging a target to use known plaintext in an encrypted message, typically by performing some action the target is sure to report. It was a term used during World War II at the British Government Code and Cypher School at Bletchley Park, England, for schemes to entice the Germans to include particular words, which the British called "cribs", in their encrypted messages. This term presumably came from RAF minelaying missions, or "gardening" sorties. "Gardening" was standard RAF slang for sowing mines in rivers, ports and oceans from low heights, possibly because each sea area around the European coasts was given a code-name of flowers or vegetables.
The technique is claimed to have been most effective against messages produced by the German Navy's Enigma machines. If the Germans had recently swept a particular area for mines, and analysts at Bletchley Park were in need of some cribs, they might (and apparently did on several occasions) request that the area be mined again. This would hopefully evoke encrypted messages from the local command mentioning Minen (German for mines), the location, and perhaps messages also from the headquarters with minesweeping ships to assign to that location, mentioning the same. It worked often enough to try several times.
This crib-based decryption is usually not considered a chosen-plaintext attack, even though plain text effectively chosen by the British was injected into the ciphertext, because the choice was very limited and the cryptanalysts did not care what the crib was so long as they knew it. Most chosen-plaintext cryptanalysis requires very specific patterns (e.g. long repetitions of "AAA...", "BBB...", "CCC...", etc.) which could not be mistaken for normal messages. It does, however, show that the boundary between these two is somewhat fuzzy.
Another notable example occurred during the lead up to the Battle of Midway. U.S. cryptanalysts had decrypted numerous Japanese messages about a planned operation at "AF", but the code word "AF" came from a second location code book which was not known. Suspecting it was Midway island, they arranged for the garrison there to report in the clear about a breakdown of their desalination plant. A Japanese report about "AF" being short of fresh water soon followed, confirming the guess.
See also
Cryptanalysis of the Enigma
Known-plaintext attack
Notes
Cryptographic attacks
Bletchley Park | Gardening (cryptanalysis) | Technology | 540 |
18,865,642 | https://en.wikipedia.org/wiki/Supersymmetry%20algebra | In theoretical physics, a supersymmetry algebra (or SUSY algebra) is a mathematical formalism for describing the relation between bosons and fermions. The supersymmetry algebra contains not only the Poincaré algebra and a compact subalgebra of internal symmetries, but also contains some fermionic supercharges, transforming as a sum of N real spinor representations of the Poincaré group. Such symmetries are allowed by the Haag–Łopuszański–Sohnius theorem. When N>1 the algebra is said to have extended supersymmetry. The supersymmetry algebra is a semidirect sum of a central extension of the super-Poincaré algebra by a compact Lie algebra B of internal symmetries.
Bosonic fields commute while fermionic fields anticommute. In order to have a transformation that relates the two kinds of fields, the introduction of a Z2-grading under which the even elements are bosonic and the odd elements are fermionic is required. Such an algebra is called a Lie superalgebra.
Just as one can have representations of a Lie algebra, one can also have representations of a Lie superalgebra, called supermultiplets. For each Lie algebra, there exists an associated Lie group which is connected and simply connected, unique up to isomorphism, and the representations of the algebra can be extended to create group representations. In the same way, representations of a Lie superalgebra can sometimes be extended into representations of a Lie supergroup.
Structure of a supersymmetry algebra
The general supersymmetry algebra for spacetime dimension d, and with the fermionic piece consisting of a sum of N irreducible real spinor representations, has a structure of the form
(P×Z).Q.(L×B)
where
P is a bosonic abelian vector normal subalgebra of dimension d, normally identified with translations of spacetime. It is a vector representation of L.
Z is a scalar bosonic algebra in the center whose elements are called central charges.
Q is an abelian fermionic spinor subquotient algebra, and is a sum of N real spinor representations of L. (When the signature of spacetime is divisible by 4 there are two different spinor representations of L, so there is some ambiguity about the structure of Q as a representation of L.) The elements of Q, or rather their inverse images in the supersymmetry algebra, are called supercharges. The subalgebra (P×Z).Q is sometimes also called the supersymmetry algebra and is nilpotent of length at most 2, with the Lie bracket of two supercharges lying in P×Z.
L is a bosonic subalgebra, isomorphic to the Lorentz algebra in d dimensions, of dimension d(d–1)/2
B is a scalar bosonic subalgebra, given by the Lie algebra of some compact group, called the group of internal symmetries. It commutes with P,Z, and L, but may act non-trivially on the supercharges Q.
The terms "bosonic" and "fermionic" refer to even and odd subspaces of the superalgebra.
The terms "scalar", "spinor", "vector", refer to the behavior of subalgebras under the action of the Lorentz algebra L.
The number N is the number of irreducible real spin representations. When the signature of spacetime is divisible by 4 this is ambiguous as in this case there are two different irreducible real spinor representations, and the number N is sometimes replaced by a pair of integers (N1, N2).
The supersymmetry algebra is sometimes regarded as a real super algebra, and sometimes as a complex algebra with a hermitian conjugation. These two views are essentially equivalent, as the real algebra can be constructed from the complex algebra by taking the skew-Hermitian elements, and the complex algebra can be constructed from the real one by taking tensor product with the complex numbers.
The bosonic part of the superalgebra is isomorphic to the product of the Poincaré algebra P.L with the algebra Z×B of internal symmetries.
When N>1 the algebra is said to have extended supersymmetry.
When Z is trivial, the subalgebra P.Q.L is the super-Poincaré algebra.
See also
Adinkra symbols
Super-Poincaré algebra
Superconformal algebra
Supersymmetry algebras in 1 + 1 dimensions
N = 2 superconformal algebra
References
Supersymmetry
Lie algebras | Supersymmetry algebra | Physics | 998 |
28,235,575 | https://en.wikipedia.org/wiki/Swarts%20fluorination | Swarts fluorination is a process whereby the chlorine atoms in a compound – generally an organic compound, but experiments have been performed using silanes – are replaced with fluorine, by treatment with antimony trifluoride in the presence of chlorine or of antimony pentachloride. Some metal fluorides are particularly more useful than others, including silver(I) fluoride, mercurous fluoride, cobalt(II) fluoride and aforementioned antimony.
Heating the mixture of the metal fluoride and the haloalkane (chlorine and bromine are replaced readily) yields the desired fluoroalkane. In some particularly reactive cases, heating is unnecessary; shaking or stirring the reaction mixture is sufficient. This reaction has a good yield.
The process was initially described by Frédéric Jean Edmond Swarts in 1892.
Mechanism
The active species is antimony trifluorodichloride 2, which is produced in situ from the reaction between antimony trifluoride 1 and chlorine; this compound can also be produced in bulk, according to a patent of John Weaver. This then undergoes a halogen exchange with a haloalkane (here trichloroethylsilane), as in 3, replacing the halogen atom (here chlorine) with fluorine and affording the fluorinated product 4.
References
Halogenation reactions
Substitution reactions
Name reactions | Swarts fluorination | Chemistry | 300 |
49,309,525 | https://en.wikipedia.org/wiki/Pholiota%20gummosa | Pholiota gummosa, commonly known as the sticky scalycap, is a common species of mushroom-forming fungus in the family Strophariaceae. It is found in Europe and North America, where it grows as a saprotroph on the rotting wood of deciduous trees, including trunks and roots. It can also grow on wood buried near the surface, making it seem as if it is fruiting in grass.
Taxonomy
The fungus was originally described by Wilhelm Gottfried Lasch in 1828, as a member of the genus Agaricus. After being shuffled to several different genera in its taxonomic history, it was transferred to Pholiota by Rolf Singer in 1951.
Description
The fungus makes fruitbodies with straw-yellow to beige caps measuring in diameter. The crowded gills on the cap underside have an adnate attachment to the stipe. Initially pale yellow, they turn brownish in age as the spores mature. The mushroom makes a brown spore print. Spores are smooth, thin-walled, somewhat bean-shaped (subphaseoliform), and measure 6–8 by 3.5–4.5 μm.
See also
List of Pholiota species
References
External links
Fungi described in 1828
Fungi of Europe
Fungi of North America
Strophariaceae
Fungus species | Pholiota gummosa | Biology | 260 |
7,513,144 | https://en.wikipedia.org/wiki/Thrombopoietic%20agent | Thrombopoietic agents are drugs that induce the growth and maturation of megakaryocytes. Some of them are currently in clinical use: romiplostim, eltrombopag, oprelvekin (a recombinant interleukin 11) and thrombopoietin. Several others are under clinical investigation such as lusutrombopag and avatrombopag.
References
Drugs by mechanism of action | Thrombopoietic agent | Chemistry | 96 |
15,552,594 | https://en.wikipedia.org/wiki/Intraperitoneal%20injection | Intraperitoneal injection or IP injection is the injection of a substance into the peritoneum (body cavity). It is more often applied to non-human animals than to humans. In general, it is preferred when large amounts of blood replacement fluids are needed or when low blood pressure or other problems prevent the use of a suitable blood vessel for intravenous injection.
In humans, the method is widely used to administer chemotherapy drugs to treat some cancers, particularly ovarian cancer. Although controversial, intraperitoneal use in ovarian cancer has been recommended as a standard of care. Fluids are injected intraperitoneally in infants, also used for peritoneal dialysis.
Intraperitoneal injections are a way to administer therapeutics and drugs through a peritoneal route (body cavity). They are one of the few ways drugs can be administered through injection, and have uses in research involving animals, drug administration to treat ovarian cancers, and much more. Understanding when intraperitoneal injections can be utilized and in what applications is beneficial to advance current drug delivery methods and provide avenues for further research. The benefit of administering drugs intraperitoneally is the ability for the peritoneal cavity to absorb large amounts of a drug quickly. A disadvantage of using intraperitoneal injections is that they can have a large variability in effectiveness and misinjection. Intraperitoneal injections can be similar to oral administration in that hepatic metabolism could occur in both.
History
There are few accounts of the use of intraperitoneal injections prior to 1970. One of the earliest recorded uses of IP injections involved the insemination of a guinea-pig in 1957. The study however did not find an increase in conception rate when compared to mating. In that same year, a study injected egg whites intraperitoneally into rats to study changes in "droplet" fractions in kidney cells. The study showed that the number of small droplets decreased after administration of the egg whites, indicating that they have been changed to large droplets. In 1964, a study delivered chemical agents such as acetic acid, bradykinin, and kaolin to mice intraperitoneally in order to study a "squirming" response. In 1967, the production of amnesia was studied through an injection of physostigmine. In 1968, melatonin was delivered to rats intraperitoneally in order to study how brain serotonin would be affected in the midbrain. In 1969, errors depending on a variety of techniques of administering IP injections were analyzed, and a 12% error in placement was found when using a one-man procedure versus a 1.2% error when using a two-man procedure.
A good example of how intraperitoneal injections work is depicted through "The distribution of salicylate in mouse tissues after intraperitoneal injection" because it includes information on how a drug can travel to the blood, liver, brain, kidney, heart, spleen, diaphragm, and skeletal muscle once it has been injected intraperitoneally.
These early uses of Intraperitoneal injections provide good examples of how the delivery method can be used, and provides a base for future studies on how to properly inject mice for research.
Use in humans
Currently, there are a handful of drugs that are delivered through intraperitoneal injection for chemotherapy. They are mitomycin C, cisplatin, carboplatin, oxaliplatin, irinotecan, 5-fluorouracil, gemcitabine, paclitaxel, docetaxel, doxorubicin, premetrexed, and melphalan. There needs to be more research done to determine appropriate dosing and combinations of these drugs to advance intraperitoneal drug delivery.
There are few examples of the use of intraperitoneal injections in humans cited in literature because it is mainly used to study the effects of drugs in mice. The few examples that do exist pertain to the treatment of pancreatic/ovarian cancers and injections of other drugs in clinical trials. One study utilized IP injections to study pain in the abdomen after a hysterectomy when administering anesthetic continuously vs patient-controlled. The results depicted that ketobemidone consumption was significantly lower when patients controlled anesthetic through IP. This led to the patients being able to be discharged earlier than when anesthesia was administered continuously. These findings could be advanced by studying how the route of injection affects the organs in the peritoneal cavity.
In another Phase I clinical trial, patients with ovarian cancer were injected intraperitoneally with dl1520 in order to study the effects of a replication-competent/-selective virus. The effects of this study were the onset of flu-like symptoms, emesis, and abdominal pain. The study overall defines appropriate doses and toxicity levels of dl1520 when injected intraperitoneally.
One study attempted to diagnose hepatic hydrothorax with the use of injecting Sonazoid intraperitoneally. Sonazoid was utilized to aid with contrast-enhanced ultrasonography by enhancing the peritoneal and pleural cavities. This study demonstrates how intraperitoneal injections can be used to help diagnose diseases by providing direct access to the peritoneal cavity and affecting the organs in the cavity.
In a case of a ruptured hepatocellular carcinoma, it was reported that the patient was treated successfully through the use of an intraperitoneal injection of OK-432, which is an immunomodulatory agent. The patient was a 51-year-old male who was hospitalized. The delivery of OK-432 occurred a total of four times in a span of one week. The results of this IP injection were the disappearance of the ascites associated with the rupture. This case is a good example of how IP injections can be used to deliver a drug that can help to treat or cure a medical diagnosis over the use of other routes of delivery. The results set a precedent of how other drugs may be delivered in this way to treat other similar medical issues after further research.
In 2018, a patient with stage IV ovarian cancer and peritoneal metastases was injected intraperitoneally with 12g of mixed cannabinoid before later being hospitalized. The symptoms of this included impairment of cognitive and psychomotor abilities. Because of the injection of cannabis, the patient was predicted to have some level of THC in the blood from absorption. This case presents the question of how THC is absorbed in the peritoneal cavity. It also shows how easily substances are absorbed through the peritoneal cavity after an IP injection.
Overall, this section provides a few examples of the effects and uses of intraperitoneal injections in human patients. There are a variety of uses and possibilities for many more in the future with further research and approval.
Use in laboratory animals
Intraperitoneal injections are the preferred method of administration in many experimental studies due to the quick onset of effects post injection. This allows researchers to observe the effects of a drug in a shorter period of time, and allows them to study the effects of drugs on multiple organs that are in the peritoneal cavity at once. In order to effectively administer drugs through IP injections, the stomach of the animal is exposed, and the injection is given in the lower abdomen. The most efficient method to inject small animals is a two-person method where one holds the rodent and the other person injects the rodent at about 10 to 20 degrees in mice and 20 to 45 degrees in rats. The holder retains the arms of the animal and tilts the head lower than the abdomen to create optimal space in the peritoneal cavity.
There has been some debate on whether intraperitoneal injections are the best route of administration for experimental animal studies. It was concluded in a review article that utilizing IP injections to administer drugs to laboratory rodents in experimental studies is acceptable when being applied to proof-of-concept studies.
A study was conducted to determine the best route of administration to transplant mesenchymal stem cells for colitis. This study compared intraperitoneal injections, intravenous injections, and anal injections. It was concluded that the intraperitoneal injection had the highest survival rate of 87.5%. This study shows how intraperitoneal injections can be more effective and beneficial than other traditional routes of administration.
One article reviews the injection of sodium pentobarbital to euthanize rodents intraperitoneally. Killing the rodent through an intraperitoneal route was originally recommended over other routes such as inhalants because it was thought to be more efficient and ethical. The article overviews whether IP is the best option for euthanization based on evidence associated with welfare implications. It was concluded that there is evidence that IP may not be the best method of euthenasia due to possibilities of missinjection.
Another example of how intraperitoneal injections are used in studies involving rodents is the use of IP for micro-CT contrast enhanced detection of liver tumors. Contrast agents were administered intraperitoneally instead of intravenously to avoid errors and challenges. It was determined that IP injections are a good option for Fenestra to quantify liver tumors in mice.
An example of how intraperitoneal injections can be optimized is depicted in a study where IP injections are used to deliver anesthesia to mice. This study goes over the dosages, adverse effects, and more of using intraperitoneal injections of anesthesia.
An example of when intraperitoneal injections are not ideal is given in a study where the best route of administration was determined for cancer biotherapy. It was concluded that IP administration should not be used over intravenous therapy due to high radiation absorption in the intestines. This shows an important limitation to the use of IP therapy.
The provided examples show a variety of uses for intraperitoneal injections in animals for in vitro studies. Some of the examples depict situations where IP injections are not ideal, while others prove the advantageous uses if this delivery method. Overall, many studies utilize IP injections to deliver therapeutics to lab animals due to the efficiency of the administration route.
References
Medical treatments
Routes of administration
Dosage forms
Digestive system procedures | Intraperitoneal injection | Chemistry | 2,212 |
53,989,605 | https://en.wikipedia.org/wiki/Polyrotaxane | Polyrotaxane is a type of mechanically interlocked molecule consisting of strings and rings, in which multiple rings are threaded onto a molecular axle and prevented from dethreading by two bulky end groups. As oligomeric or polymeric species of rotaxanes, polyrotaxanes are also capable of converting energy input to molecular movements because the ring motions can be controlled by external stimulus. Polyrotaxanes have attracted much attention for decades, because they can help build functional molecular machines with complicated molecular structure.
Although there are no covalent bonds between the axes and rings, polyrotaxanes are stable due to the high free activation energy (Gibbs energy) needed to be overcome to withdraw rings from the axes. Also, rings are capable of shuttling along and rotating around the axes freely, which leads to a huge amount of internal degree of freedom of polyrotaxanes. Due to this topologically interlocked structure, polyrotaxanes have many different mechanical, electrical, and optical properties compared to conventional polymers.
Additionally the mechanically interlocked structures can be maintained in slide-ring materials, which are a type supramolecular network synthesized by crosslinking the rings (called figure-of-eight crosslinking) in different polyrotaxanes. In slide-ring materials, crosslinks of rings can pass along the axes freely to equalize the tension of the threading polymer networks, which is similar to pulleys. With this specific structure, slide-ring materials can be fabricated highly stretchable engineering materials due to their different mechanical properties.
If the rings and axes are biodegradable and biocompatible, the polyrotaxanes can also be used for biomedical application, such as gene/drug delivery. The advantage of polyrotaxanes over other biomedical polymers, such as polysaccharides, is that because the interlocked structures are maintained by bulky stoppers at the ends of the strings, if the bulky stoppers are removed, such as removed by a chemical stimulus, rings dethread from the axes. The drastic structural change can be used for programmed drug or gene delivery, in which the drug or gene can be released with the rings when the stoppers are cut off at the specific destination.
Types of polyrotaxanes
According to the location of the rotaxanes units, polyrotaxanes can be mainly divided into two types: main chain polyrotaxanes, in which the rotaxane units locate on the main chain (axis), and side chain polyrotaxanes, in which the rotaxane units are located on the side chain. Corresponding polypseudorotaxanes can also be divided based on the same principle: main chain polypseudorotaxnes or side chain polypseudorotaxanes, in which there is no stopper at the ends.
In both main chain polyrotaxanes or side chain polyrotaxanes, the unique feature from other polymers is the potential for different motion of the ring unit relative to the string units. Because the shape and location of the assembly are capable of showing different responses to changes in temperature, pH or other environment conditions, polyrotaxanes have many distinctive properties.
Main chain polyrotaxanes
Main chain polyrotaxanes are formed by host–guest interactions of polymer backbones (main chain) with cyclic molecules that are interlocked by bulky stoppers.
There are five major synthesis routes for main chain polyrotaxanes.
(1) Cyclization in the presence of main chain.
This synthesis route requires high dilution conditions of cyclization reactions. However, to most cases, it is difficult to sustain the high dilution conditions for rotaxane formation. Other possible methods to solve this problem are template cyclizations, such as cyclization based on metal chelation, change-transfer complexation or inclusion complexes.
(2) Polymerization of monomeric rotaxanes units.
Through polymerizing stable rotaxane monomers, polyrotaxanes are obtained. This method requires that the monomeric rotaxane units are stable in the solvent and have active groups that can be polymerized, which means the rings will not dethread from the main chain.
(3) Chemical conversion.
Specially designed linear polymers are required in this method. Designed monomers are polymerized to obtain special linear polymers with precursors of cyclic compounds. After bulky stoppers are modified onto two sides of polymer chains, the "temporary" chemical bonds in the precursors are cleaved to generate cyclic structure on the main chain, which becomes a polyrotaxane. The disadvantage of this method is the complex chemistry needed in the process of design and synthesis of the special linear polymers with precursors and the transitions to polyrotaxanes, e.g. the selective chemical bond cleavage. Many synthesis steps are required in this method.
(4) Threading of preformed main chain molecules through preformed rings.
The fourth approach is the simplest method to synthesize polyrotaxanes. Through mixing the main chain polymers and the rings in the solution, polyrotaxanes can be obtained after adding bulky stoppers to prevent the rings from dethreading from the chains. The number of rings on each chain depends on the threading equilibrium. Kinetic limitations due to the low concentration of chain ends and entropic effects also need further consideration. To overcome these obstacles, template threading (see below) is also a feasible alternative that can improve dynamically the number of threading rings by changing the equilibrium constant.
(5) Production of linear macromolecule in the presence of preformed rings.
Two general methods are included in this approach: the "statistical approach" and "template threading approach".
In the "statistical approach", the interaction between rings and strings is weakly attractive or repulsive or even negligible. Through employing an excess of rings, the equilibrium for threading or dethreading is forced to the threading side before polymerization. Compared with synthesis route 1, rings are a major constituent of the system instead of the rotaxanes, so the high dilution conditions are not required for this methods.
In "template threading approach", unlike the statistical approach, the interactions between rings and strings need to be attractive, such as metal chelations or charge transfer interactions which have been mentioned in the synthesis route 1. Because of this, the equilibrium is enthalpically driven, where the enthalpy is negative. In this method, high numbers of threading rings can be achieved, thus it is a useful way to stoichiometrically control the rings ratio of polyrotaxanes.
An example of the "statistical approach" is that a polyrotaxane was synthesized through polymerizing the rotaxane monomer that was assembled by oligomeric ethylene glycols (string) and crown ethers (ring) and naphthalene-1,5-di-isocyanate (stopper), which involves the threading equilibrium in the chain-ring system.
Cyclodextrins have been extensively studied as host molecules (ring) in polyrotaxanes. The poly(ethylene glycol)s can assemble with α-cyclodextrins to form a molecular necklace. Every two ethyleneoxy repeat units in poly(ethylene glycol)s can thread in one α-cyclodextrin. The models confirm that the distance of form zig-zag structure of repeat units corresponds to the size of cavity in α-cyclodextrins. This is a classical example of "template threadings" which also explains why poly(ethylene glycol)s are not able to form rotaxanes with β-cyclodextrin.
Crown ethers are another type of monomacrocyclic polymers that are used in synthesis of polyrotaxanes. The polyrotaxanes can be prepared by carrying out step-growth polymerizations in the presence of aliphatic crown ethers. In most of the cases, hydrogen bonding between the crown ethers and OH or NH/NHCO moieties are involved in the form of the assemblies. The threading efficiency will increase with the growth of sizes of the crown molecules. Additionally, stoppers will also greatly increase the threading efficiency.
Metal coordination also can be used to construct polyrotaxane structures. In this method, metal ions are employed as the synthesis templates to determine the coordinating sites of rotaxane structures. Conjugated polyrotaxanes can be synthesized through metal-template strategies followed by electropolymerization that ensures tuning of the electronic coupling between the ring cites and the conjugated backbone (string).
Side chain polyrotaxanes
Side chain polyrotaxanes are formed by host–guest interactions of polymer side chains with cyclic molecules that are interlocked by bulky stoppers.
There are mainly three types of side chain polyrotaxanes:
(1) Polyaxis/rotor: Comb-like polymers assembled with the cyclic molecules that are not interlocked on the side chain.
(2) Polyrotor/axis: polymers possess cyclic molecules on the side chain, which assemble with guest molecules to form polypseudorotaxanes.
(3) Polyrotor/polyaxis: polymers possess covalently bonded cyclic molecule-moieties assembled with polymers possess guested in the side chain.
Similar to the synthesis routes to main chain polyrotaxanes, there are mainly six approaches to side chain polyrotaxane.
(1) Ring-threading of performed graft polymer
(2) Ring-grafting
(3) Rotaxane-grafting
(4) Polymerization of macromonomer with rings
(5) Polymerization of rotaxane-monomer
(6) Chemical conversion
Similarly, the positions of chain and rings can be switched, which results in corresponding side-chain polyrotaxanes.
Properties
In a polyrotaxane, unlike a conventional polymer, the molecules are linked by mechanical bonding, such as hydrogen boding or charge transfer, not covalent bonds. Also, the rings are capable of rotating on or shuttling around the axles, resulting in the large amount of freedom of polyrotaxanes. This unconventional combination of molecules leads to the distinctive properties of polyrotaxanes.
Stability and solubility
Due to the existence of stoppers on the ends of the rotaxanes units, polyrotaxanes are more thermodynamically stable than polypseudorotaxanes (similar structure to polyrotaxane but without stoppers at two ends). Also, if the interactions between guest and host molecules are attractive, such as hydrogen bonding or charge transfer, they have better stabilities than those without attractive interactions. However, specific salts, changes of pH condition or temperature that can disturb or interrupt the interactions between ring-ring, ring-backbone, or backbone-backbone will destroy the structural integrity of polyrotaxanes. For example, dimethylformamide or dimethyl sulfoxide is able to interrupt the hydrogen bonding between cyclodextrins in the cyclodextrin-based polyrotaxanes. Also, change of pH or high temperature can also destroy the crystalline domains. Some chemical bonds between stoppers and chains are not stable in acidic or basic solution. As the stoppers cut from the chain, the rings will dethread from the axles, which leads to the dissociation of the polyrotaxanes.
For example, a "molecular necklace" assembled by α-cyclodextrins and polyethylene glycol is insoluble in water and dimethylfomamide, although their parents' components α-cyclodextrin and polyethylene glycol can be dissolved and this synthesis can happen in water. The product is soluble in dimethyl sulfoxide or 0.1 M sodium hydroxide solution. This is because the hydrogen bonding between the cyclodextrins. As the hydrogen bonding is destroyed by dimethyl sulfoxide or base solution, it can be dissolved, but the water does not deform the hydrogen interaction between cyclodextrins. In addition, the complexation process is exothermic in thermodynamic tests, which is also corresponding with the existence of hydrogen bonding.
Photoelectronic properties
One of the properties of polytorotaxanes involves the photoelectronic response when introducing photoactive or electrionic-active units into the mechanically interlocked structures.
For examples, the polyrotaxane structures are capable of enhancing the fluorescence quenching molecules that grafting on the rings and the other molecules at the ends. Amplification of a fluorescence chemosensory can be achieved by using polyrotaxane structure, which enhances the energy migration in the polymer. It was found that a rapid migration of the hole-electron pair to the rotaxanes sites is followed by a rapid combination which leads to the enhancement of the energy migration. In addition, the conductivity of these polyrotaxanes was lower than the parent components.
Also conductive polyrotaxanes can be obtained by employing metal binding in the polyrotaxanes structure. For example, a polyrotaxane containing a conjugated backbone can be synthesized through metal template and electropolymerization. The metal ion binding is reversible when another metal with stronger binding ability is employed to remove the previous ion, which results in the "scaffolding effect reversibility". The free coordination sites and the organic matrix are able to be maintained by the labile scaffolding.
Potential application
Molecular machines
Many mechanically interlocked molecules have been studied to construct molecular machines. Because the molecules are linked by mechanical bonds instead of conventional covalent bonds, a component can move (shuttle) or rotate around the other parent component, which results in the large amount of freedom of mechanically interlocked molecules. Polyrotaxanes, as the polymer form of corresponding rotaxanes, are also applied in molecular machines.
For example, the shuttling behavior of the molecular shuttle can be controlled by the solvent or temperature. Due to the hydrophobic interaction between rings and strings, and the repulsive interaction between rings and linkers, conditions that are capable of influencing these interactions can be used to control the mobility of the rings in the molecular shuttle. In addition, if cationic or anionic units are employed to form the polyrotaxanes, the salts or pH in the solution also will influence the charge interactions between rings and strings, which is an alternative method to control the ring motion of the molecular shuttle.
Poly[2]rotaxane "daisy chains" (like a string of daisies with stems linked to form a chain)is an example of a molecule that can be used to form a molecular muscle. Poly[2]rotaxane can expand or shrink in response to external stimulus, which is similar to behaviors of muscle, an ideal model to construct a "molecular muscle". The ring stations on the chain can be controlled by pH or light. Due to "daisy chain" structure, two rings on the daisy chain will shift from one station to another station, which changes the distance between two rings as well as the state of the whole daisy chain. When the rings come close, the whole size of the daisy chain will increase, which is the "expand" state. As the rings get to the further station, the molecule become the "shrink" state as the decreased size.
Slide-ring materials
By chemically crosslinking the rings contained in the polyrotaxanes, sliding gels are obtained by being topologically interlocked by figure-of-eight crosslinks. Although it is a polymer network (gel), the rings are not fixed on the polyrotaxanes in the polymer network, the crosslinks of rings are able to freely move along the polymer chain. This can equalize the tension of the network, just like a pulley manner, which is referred to pulley effect. In chemical gels, the polymer chains are easy to be broken because the lengths of the heterogeneous polymer are limited or fixed. As a result, when the chemical gel is under a high pressure, the tension can not be equalized to the whole. On the opposite, the weakest part in the network will be broken easier, which leads to the damage of the gel. However, in the slide-ring materials, the polymer chain are able to pass through the figure-of-eight crosslinks which is like pulleys, and equalize the tension of network. As a result, slide-ring materials are applied to construct highly stretchable materials, up to 24 times its length when stretching and this process can be reversible.
Drug/gene delivery
Although polyrotaxanes are formed from components, their solubilities are different from the host or guest molecules. For examples, in the cyclodextrin-based polyrotaxanes, due to the hydrophilicity or high polarity of exterior structure of the cyclodextrins, some polyrotaxanes are able to be dissolved in water or other polar solvents though the guest molecules are hydrophobic or nonpolar. These water-soluble can be applied into drug or gene carriers.
There are two main advantages for polyrotaxanes applied to drug/gene delivery:
Targeting
Because the mechanically interlocked structures are maintained by bulky stoppers at the ends of the strings, if the bulky stoppers are removed, such as removed by a chemical stimulus, rings dethread from the axes. The drastic structural change can be used for programmed drug or gene delivery, of which drug or gene can be released with the rings when the stoppers are cut off at the specific destination.
For example, an enhanced gene delivery vehicle can be obtained by using a polyrotaxane formed by rings, backbones, then stoppers that linked by a disulfide bond (or other chemical bond that can be selected cleave in the body). The cation-functionalized polyrotaxanes can bind with pDNA to form complex through the electronstatic interaction. Glutathione (or other corresponding chemicals that can cleave the sensitive chemical bond) is over-expressed in the target cells. When the polyrotaxane/plasmid DNA (pDNA) complexes are uptaken by the target cells, intercellular glutathione could cleave the disulfide bond to cut off the stoppers at the end of polyrotaxanes, which results in the dissociation of the polyrotaxanes. As the rings dethread from the chain, pDNA is released with the ring molecules.
Long-term controlled release
Another advantage of poly(pseudo)rotaxanes is the ability for long-term release of drugs or genes. Some polyrotaxanes can used to form a physical hydrogel, which is called supramolecular hydrogel. In these cases, a three-dimensional physically crosslinked network formed by the poly(pseudo)rotaxanes, can be obtained, which is able to retain a large amount of water inside this network. If water-soluble drugs or genes are added in the solution, it could be capsulated in the supramolecular hydrogels. Also, functional units can be employed in the units of the poly(pseudo)rotaxanes, which enhances the interaction between the poly(pseudo)rotaxanes and capsulated drugs/genes and provides the carriers with other predetermined functions. As the network is further swollen in the water-based environment, part of the carrier will be dissolved gradually, so the capsulated drug or gene can be released from the hydrogels over a long period of time.
See also
Polyrotaxane-based paint
References
Supramolecular chemistry | Polyrotaxane | Chemistry,Materials_science | 4,167 |
8,984,724 | https://en.wikipedia.org/wiki/Dirichlet%20algebra | In mathematics, a Dirichlet algebra is a particular type of algebra associated to a compact Hausdorff space X. It is a closed subalgebra of C(X), the uniform algebra of bounded continuous functions on X, whose real parts are dense in the algebra of bounded continuous real functions on X. The concept was introduced by .
Example
Let be the set of all rational functions that are continuous on ; in other words functions that have no poles in . Then
is a *-subalgebra of , and of . If is dense in , we say is a Dirichlet algebra.
It can be shown that if an operator has as a spectral set, and is a Dirichlet algebra, then has a normal boundary dilation. This generalises Sz.-Nagy's dilation theorem, which can be seen as a consequence of this by letting
References
Completely Bounded Maps and Operator Algebras Vern Paulsen, 2002
.
Functional analysis
C*-algebras | Dirichlet algebra | Mathematics | 202 |
2,879,824 | https://en.wikipedia.org/wiki/List%20of%20Japanese%20map%20symbols | This is a list of symbols appearing on Japanese maps. These symbols are called in the Japanese language.
Partial list of symbols for users with visual impairment
Official symbols according to the conventions of the Geographical Survey Institute of Japan appear with a circle below.
See also
(GSI)
External links
Japanese map symbols
This is a very good reference, it has separate links for each symbol.
Japanese map
Maps of Japan
Geography of Japan
Japan | List of Japanese map symbols | Mathematics | 85 |
59,545,820 | https://en.wikipedia.org/wiki/NGC%206907 | NGC 6907 is a spiral galaxy located in the constellation Capricornus. It is located at a distance of about 120 million light-years from Earth, which, given its apparent dimensions, means that NGC 6907 is about 115,000 light-years across. It was discovered by William Herschel on July 12, 1784. The total infrared luminosity of the galaxy is , and thus it is categorised as a luminous infrared galaxy.
Characteristics
NGC 6907 is a grand design spiral galaxy with two spiral arms. It has an elliptical bulge that is skewed towards the base of the arms. The inner arms are bright and with knots, forming a bar. There are dust lanes in the arms. The disk of NGC 6907 is asymmetric. The eastern arm changes pitch angle and becomes linear after the location of the nearby galaxy NGC 6908. The western arm is less strong, but it is considerably longer, as its outermost parts form an arc with H II regions, wrapping nearly 360 degrees around the disk and forming a pseudoring. NGC 6907 also has a tidal tail with low surface brightness. The asymmetric tail extends from the north part of the disk of the galaxy towards the west and southwest. Its presence is an indicator of an ongoing unequal mass merger. The total HI mass of NGC 6907 is estimated to be .
NGC 6907 interacts with a low-luminosity lenticular galaxy, known as NGC 6908, that is superimposed on the eastern arm of NGC 6907, lying 40 arcseconds off the nucleus of NGC 6907. NGC 6908 was thought for many years to be actually part of NGC 6907, which was described as having two massive asymmetric arms; however, when observed in infrared, it becomes apparent NGC 6908 is a different galaxy. As NGC 6908 passed through the disk of NGC 6907, a stellar and gas bridge was formed between the two galaxies that has been observed as high-velocity gas. It is estimated that NGC 6908 passed through the disk approximately 35 million years ago.
Nearby galaxies
NGC 6907 is the more prominent member of a small galaxy group known as the NGC 6907 group or LGG 436. Other members of the group, apart from NGC 6908, include IC 4999 and IC 5005. These two galaxies lie 61 and 74 arcminutes off NGC 6907, respectively. The group seems to form, with some other galaxies lying at similar redshift, like ESO 462- G016, a sheet of galaxies that extends 10 degrees in the sky, which corresponds to 7 Mpc at the distance of NGC 6907.
Supernovae
NGC 6907 has been home to four supernovae:
SN 1984V (type unknown, mag 15.0) was discovered by L. E. Gonzalez on 29 May 1984.
SN 2004bv (type Ia, mag 15.6) was discovered by R. Kushida on 24 May 2004.
SN 2008fq (Type II, mag 15.4) was discovered by the Lick Observatory Supernova Search (LOSS) on 15 September 2008.
SN 2014eh (Type Ic, mag 16.0) was discovered by LOSS on 28 October 2014.
Gallery
See also
NGC 1097 – another spiral galaxy with a smaller companion
References
External links
NGC 6907 on SIMBAD
Barred spiral galaxies
Luminous infrared galaxies
Capricornus
6907
UGCA objects
64650
Astronomical objects discovered in 1784
Discoveries by William Herschel | NGC 6907 | Astronomy | 719 |
268,420 | https://en.wikipedia.org/wiki/Foam | Foams are two-phase material systems where a gas is dispersed in a second, non-gaseous material, specifically, in which gas cells are enclosed by a distinct liquid or solid material. The foam "may contain more or less liquid [or solid] according to circumstances", although in the case of gas-liquid foams, the gas occupies most of the volume. The word derives from the medieval German and otherwise obsolete veim, in reference to the "frothy head forming in the glass once the beer has been freshly poured" (cf. ausgefeimt).
Theories regarding foam formation, structure, and properties—in physics and physical chemistry—differ somewhat between liquid and solid foams in that the former are dynamic (e.g., in their being "continuously deformed"), as a result of gas diffusing between cells, liquid draining from the foam into a bulk liquid, etc. Theories regarding liquid foams have as direct analogs theories regarding emulsions, two-phase material systems in which one liquid is enclosed by another.
In most foams, the volume of gas is large, with thin films of liquid or solid separating the regions of gas. A bath sponge and the head on a glass of beer are examples of foams; soap foams are also known as suds.
Solid foams can be closed-cell or open-cell. In closed-cell foam, the gas forms discrete pockets, each completely surrounded by the solid material. In open-cell foam, gas pockets connect to each other. A bath sponge is an example of an open-cell foam: water easily flows through the entire structure, displacing the air. A sleeping mat is an example of a product composed of closed-cell foam.
Foams are examples of dispersed media. In general, gas is present, so it divides into gas bubbles of different sizes (i.e., the material is polydisperse)—separated by liquid regions that may form films, thinner and thinner when the liquid phase drains out of the system films. When the principal scale is small, i.e., for a very fine foam, this dispersed medium can be considered a type of colloid.
Foam can also refer to something that is analogous to foam, such as quantum foam.
Structure
A foam is, in many cases, a multi-scale system.
One scale is the bubble: material foams are typically disordered and have a variety of bubble sizes. At larger sizes, the study of idealized foams is closely linked to the mathematical problems of minimal surfaces and three-dimensional tessellations, also called honeycombs. The Weaire–Phelan structure is reported in one primary philosophical source to be the best possible (optimal) unit cell of a perfectly ordered foam, while Plateau's laws describe how soap-films form structures in foams.
At lower scale than the bubble is the thickness of the film for metastable foams, which can be considered a network of interconnected films called lamellae. Ideally, the lamellae connect in triads and radiate 120° outward from the connection points, known as Plateau borders.
An even lower scale is the liquid–air interface at the surface of the film. Most of the time this interface is stabilized by a layer of amphiphilic structure, often made of surfactants, particles (Pickering emulsion), or more complex associations.
Formation
Several conditions are needed to produce foam: there must be mechanical work, surface active components (surfactants) that reduce the surface tension, and the formation of foam faster than its breakdown.
To create foam, work (W) is needed to increase the surface area (ΔA):
where γ is the surface tension.
One of the ways foam is created is through dispersion, where a large amount of gas is mixed with a liquid. A more specific method of dispersion involves injecting a gas through a hole in a solid into a liquid. If this process is completed very slowly, then one bubble can be emitted from the orifice at a time as shown in the picture below.
One of the theories for determining the separation time is shown below; however, while this theory produces theoretical data that matches the experimental data, detachment due to capillarity is accepted as a better explanation.
The buoyancy force acts to raise the bubble, which is
where is the volume of the bubble, is the acceleration due to gravity, and ρ1 is the density of the gas ρ2 is the density of the liquid. The force working against the buoyancy force is the surface tension force, which is
,
where γ is the surface tension, and is the radius of the orifice.
As more air is pushed into the bubble, the buoyancy force grows quicker than the surface tension force. Thus, detachment occurs when the buoyancy force is large enough to overcome the surface tension force.
In addition, if the bubble is treated as a sphere with a radius of and the volume is substituted in to the equation above, separation occurs at the moment when
Examining this phenomenon from a capillarity viewpoint for a bubble that is being formed very slowly, it can be assumed that the pressure inside is constant everywhere. The hydrostatic pressure in the liquid is designated by . The change in pressure across the interface from gas to liquid is equal to the capillary pressure; hence,
where R1 and R2 are the radii of curvature and are set as positive. At the stem of the bubble, R3 and R4 are the radii of curvature also treated as positive. Here the hydrostatic pressure in the liquid has to take into account z, the distance from the top to the stem of the bubble. The new hydrostatic pressure at the stem of the bubble is p0(ρ1 − ρ2)z. The hydrostatic pressure balances the capillary pressure, which is shown below:
Finally, the difference in the top and bottom pressure equals the change in hydrostatic pressure:
At the stem of the bubble, the shape of the bubble is nearly cylindrical; consequently, either R3 or R4 is large while the other radius of curvature is small. As the stem of the bubble grows in length, it becomes more unstable as one of the radius grows and the other shrinks. At a certain point, the vertical length of the stem exceeds the circumference of the stem and due to the buoyancy forces the bubble separates and the process repeats.
Stability
Stabilization
The stabilization of foam is caused by van der Waals forces between the molecules in the foam, electrical double layers created by dipolar surfactants, and the Marangoni effect, which acts as a restoring force to the lamellae.
The Marangoni effect depends on the liquid that is foaming being impure. Generally, surfactants in the solution decrease the surface tension. The surfactants also clump together on the surface and form a layer as shown below.
For the Marangoni effect to occur, the foam must be indented as shown in the first picture. This indentation increases the local surface area. Surfactants have a larger diffusion time than the bulk of the solution—so the surfactants are less concentrated in the indentation.
Also, surface stretching makes the surface tension of the indented spot greater than the surrounding area. Consequentially—since the diffusion time for the surfactants is large—the Marangoni effect has time to take place. The difference in surface tension creates a gradient, which instigates fluid flow from areas of lower surface tension to areas of higher surface tension. The second picture shows the film at equilibrium after the Marangoni effect has taken place.
Curing a foam solidifies it, making it indefinitely stable at STP.
Destabilization
Witold Rybczynski and Jacques Hadamard developed an equation to calculate the velocity of bubbles that rise in foam with the assumption that the bubbles are spherical with a radius .
with velocity in units of centimeters per second. ρ1 and ρ2 is the density for a gas and liquid respectively in units of g/cm3 and ῃ1 and ῃ2 is the dynamic
viscosity of the gas and liquid respectively in units of g/cm·s and g is the acceleration of gravity in units of cm/s2.
However, since the density and viscosity of a liquid is much greater than the gas, the density and viscosity of the gas can be neglected, which yields the new equation for velocity of bubbles rising as:
However, through experiments it has been shown that a more accurate model for bubbles rising is:
Deviations are due to the Marangoni effect and capillary pressure, which affect the assumption that the bubbles are spherical.
For laplace pressure of a curved gas liquid interface, the two principal radii of curvature at a point are R1 and R2. With a curved interface, the pressure in one phase is greater than the pressure in another phase. The capillary pressure Pc is given by the equation of:
,
where is the surface tension. The bubble shown below is a gas (phase 1) in a liquid (phase 2) and point A designates the top of the bubble while point B designates the bottom of the bubble.
At the top of the bubble at point A, the pressure in the liquid is assumed to be p0 as well as in the gas. At the bottom of the bubble at point B, the hydrostatic pressure is:
where ρ1 and ρ2 is the density for a gas and liquid respectively. The difference in hydrostatic pressure at the top of the bubble is 0, while the difference in hydrostatic pressure at the bottom of the bubble across the interface is gz(ρ2 − ρ1). Assuming that the radii of curvature at point A are equal and denoted by RA and that the radii of curvature at point B are equal and denoted by RB, then the difference in capillary pressure between point A and point B is:
At equilibrium, the difference in capillary pressure must be balanced by the difference in hydrostatic pressure. Hence,
Since, the density of the gas is less than the density of the liquid the left hand side of the equation is always positive. Therefore, the inverse of RA must be larger than the RB. Meaning that from the top of the bubble to the bottom of the bubble the radius of curvature increases. Therefore, without neglecting gravity the bubbles cannot be spherical. In addition, as z increases, this causes the difference in RA and RB too, which means the bubble deviates more from its shape the larger it grows.
Foam destabilization occurs for several reasons. First, gravitation causes drainage of liquid to the foam base, which Rybczynski and Hadamar include in their theory; however, foam also destabilizes due to osmotic pressure causes drainage from the lamellas to the Plateau borders due to internal concentration differences in the foam, and Laplace pressure causes diffusion of gas from small to large bubbles due to pressure difference. In addition, films can break under disjoining pressure, These effects can lead to rearrangement of the foam structure at scales larger than the bubbles, which may be individual (T1 process) or collective (even of the "avalanche" type).
Mechanical properties
Liquid foams
Solid foams
Solid foams, both open-cell and closed-cell, are considered as a sub-class of cellular structures. They often have lower nodal connectivity as compared to other cellular structures like honeycombs and truss lattices, and thus, their failure mechanism is dominated by bending of members. Low nodal connectivity and the resulting failure mechanism ultimately lead to their lower mechanical strength and stiffness compared to honeycombs and truss lattices.
The strength of foams can be impacted by the density, the material used, and the arrangement of the cellular structure (open vs closed and pore isotropy). To characterize the mechanical properties of foams, compressive stress-strain curves are used to measure their strength and ability to absorb energy since this is an important factor in foam based technologies.
Elastomeric foam
For elastomeric cellular solids, as the foam is compressed, first it behaves elastically as the cell walls bend, then as the cell walls buckle there is yielding and breakdown of the material until finally the cell walls crush together and the material ruptures. This is seen in a stress-strain curve as a steep linear elastic regime, a linear regime with a shallow slope after yielding (plateau stress), and an exponentially increasing regime. The stiffness of the material can be calculated from the linear elastic regime where the modulus for open celled foams can be defined by the equation:
where is the modulus of the solid component, is the modulus of the honeycomb structure, is a constant having a value close to one, is the density of the honeycomb structure, and is the density of the solid. The elastic modulus for closed cell foams can be described similarly by:
where the only difference is the exponent in the density dependence. However, in real materials, a closed-cell foam has more material at the cell edges which makes it more closely follow the equation for open-cell foams. The ratio of the density of the honeycomb structure compared with the solid structure has a large impact on the modulus of the material. Overall, foam strength increases with density of the cell and stiffness of the matrix material.
Energy of deformation
Another important property which can be deduced from the stress strain curve is the energy that the foam is able to absorb. The area under the curve (specified to be before rapid densification at the peak stress), represents the energy in the foam in units of energy per unit volume. The maximum energy stored by the foam prior to rupture is described by the equation:
This equation is derived from assuming an idealized foam with engineering approximations from experimental results. Most energy absorption occurs at the plateau stress region after the steep linear elastic regime.
Directional dependence
The isotropy of the cellular structure and the absorption of fluids can also have an impact on the mechanical properties of a foam. If there is anisotropy present, then the materials response to stress will be directionally dependent, and thus the stress-strain curve, modulus, and energy absorption will vary depending on the direction of applied force. Also, open-cell structures which have connected pores can allow water or other liquids to flow through the structure, which can also affect the rigidity and energy absorption capabilities.
Applications
Liquid foams
Liquid foams can be used in fire retardant foam, such as those that are used in extinguishing fires, especially oil fires.
The dough of leavened bread has traditionally been understood as a closed-cell foam—yeast causing bread to rise via tiny bubbles of gas that become the bread pores—where the cells do not connect with each other. Cutting the dough releases the gas in the bubbles that are cut, but the gas in the rest of the dough cannot escape. When dough is allowed to rise too far, it becomes an open-cell foam, in which the gas pockets are connected; cutting the dough surface at that point would cause a large volume of gas to escape, and the dough to collapse. Recent research has indicated that the pore structure in bread is 99% interconnected into one large vacuole, thus the closed-cell foam of the moist dough is transformed into an open cell solid foam in the bread.
The unique property of gas-liquid foams having very high specific surface area is exploited in the chemical processes of froth flotation and foam fractionation.
Depopulation
Foam depopulation or foaming is a means of mass killing farm animals by spraying foam over a large area to obstruct breathing and ultimately cause suffocation. It is usually used to attempt to stop disease spread.
Solid foams
Solid foams are a class of lightweight cellular engineering materials. These foams are typically classified into two types based on their pore structure: open-cell-structured foams (also known as reticulated foams) and closed-cell foams. At high enough cell resolutions, any type can be treated as continuous or "continuum" materials and are referred to as cellular solids, with predictable mechanical properties.
Open-cell foams can be used to filter air. For example, a foam embedded with catalyst has been shown to catalytically convert formaldehyde to benign substances when formaldehyde polluted air passes through the open cell structure.
Open-cell-structured foams contain pores that are connected to each other and form an interconnected network that is relatively soft. Open-cell foams fill with whatever gas surrounds them. If filled with air, a relatively good insulator results, but, if the open cells fill with water, insulation properties would be reduced. Recent studies have put the focus on studying the properties of open-cell foams as an insulator material. Wheat gluten/TEOS bio-foams have been produced, showing similar insulator properties as for those foams obtained from oil-based resources. Foam rubber is a type of open-cell foam.
Closed-cell foams do not have interconnected pores. The closed-cell foams normally have higher compressive strength due to their structures. However, closed-cell foams are also, in general more dense, require more material, and as a consequence are more expensive to produce. The closed cells can be filled with a specialized gas to provide improved insulation. The closed-cell structure foams have higher dimensional stability, low moisture absorption coefficients, and higher strength compared to open-cell-structured foams. All types of foam are widely used as core material in sandwich-structured composite materials.
The earliest known engineering use of cellular solids is with wood, which in its dry form is a closed-cell foam composed of lignin, cellulose, and air. From the early 20th century, various types of specially manufactured solid foams came into use. The low density of these foams makes them excellent as thermal insulators and flotation devices and their lightness and compressibility make them ideal as packing materials and stuffings.
An example of the use of azodicarbonamide as a blowing agent is found in the manufacture of vinyl (PVC) and EVA-PE foams, where it plays a role in the formation of air bubbles by breaking down into gas at high temperature.
The random or "stochastic" geometry of these foams makes them good for energy absorption, as well. In the late 20th century to early 21st century, new manufacturing techniques have allowed for geometry that results in excellent strength and stiffness per weight. These new materials are typically referred to as engineered cellular solids.
Syntactic foam
Integral skin foam
Integral skin foam, also known as self-skin foam, is a type of foam with a high-density skin and a low-density core. It can be formed in an open-mold process or a closed-mold process. In the open-mold process, two reactive components are mixed and poured into an open mold. The mold is then closed and the mixture is allowed to expand and cure. Examples of items produced using this process include arm rests, baby seats, shoe soles, and mattresses. The closed-mold process, more commonly known as reaction injection molding (RIM), injects the mixed components into a closed mold under high pressures.
Gallery
Foam scales and properties
See also
Aluminium foam sandwich
Ballistic foam
Chaotic bubble
Defoamer
Foam glass
Metal foam
Nanofoam
Sea foam
Reversibly assembled cellular composite materials
Foam party
Soft matter
References
Further reading
A modern treatise almost exclusively focused on liquid foams.
A treatise termed a classic by Weaire & Hutzler (1999), on solid foams, and the reason they limit their focus to liquid foams.
Note, this source also focuses on liquid foams.
Thomas Hipke, Günther Lange, René Poss: Taschenbuch für Aluminiumschäume. Aluminium-Verlag, Düsseldorf 2007, .
Hannelore Dittmar-Ilgen: Metalle lernen schwimmen. In: Dies.: Wie der Kork-Krümel ans Weinglas kommt. Hirzel, Stuttgart 2006, , S. 74.
External links
Andrew M. Kraynik, Douglas A. Reinelt, Frank van Swol Structure of random monodisperse foam
Colloids | Foam | Physics,Chemistry,Materials_science | 4,222 |
5,306 | https://en.wikipedia.org/wiki/Chemical%20equilibrium | In a chemical reaction, chemical equilibrium is the state in which both the reactants and products are present in concentrations which have no further tendency to change with time, so that there is no observable change in the properties of the system. This state results when the forward reaction proceeds at the same rate as the reverse reaction. The reaction rates of the forward and backward reactions are generally not zero, but they are equal. Thus, there are no net changes in the concentrations of the reactants and products. Such a state is known as dynamic equilibrium.
Historical introduction
The concept of chemical equilibrium was developed in 1803, after Berthollet found that some chemical reactions are reversible. For any reaction mixture to exist at equilibrium, the rates of the forward and backward (reverse) reactions must be equal. In the following chemical equation, arrows point both ways to indicate equilibrium. A and B are reactant chemical species, S and T are product species, and α, β, σ, and τ are the stoichiometric coefficients of the respective reactants and products:
α A + β B σ S + τ T
The equilibrium concentration position of a reaction is said to lie "far to the right" if, at equilibrium, nearly all the reactants are consumed. Conversely the equilibrium position is said to be "far to the left" if hardly any product is formed from the reactants.
Guldberg and Waage (1865), building on Berthollet's ideas, proposed the law of mass action:
where A, B, S and T are active masses and k+ and k− are rate constants. Since at equilibrium forward and backward rates are equal:
and the ratio of the rate constants is also a constant, now known as an equilibrium constant.
By convention, the products form the numerator.
However, the law of mass action is valid only for concerted one-step reactions that proceed through a single transition state and is not valid in general because rate equations do not, in general, follow the stoichiometry of the reaction as Guldberg and Waage had proposed (see, for example, nucleophilic aliphatic substitution by SN1 or reaction of hydrogen and bromine to form hydrogen bromide). Equality of forward and backward reaction rates, however, is a necessary condition for chemical equilibrium, though it is not sufficient to explain why equilibrium occurs.
Despite the limitations of this derivation, the equilibrium constant for a reaction is indeed a constant, independent of the activities of the various species involved, though it does depend on temperature as observed by the van 't Hoff equation. Adding a catalyst will affect both the forward reaction and the reverse reaction in the same way and will not have an effect on the equilibrium constant. The catalyst will speed up both reactions thereby increasing the speed at which equilibrium is reached.
Although the macroscopic equilibrium concentrations are constant in time, reactions do occur at the molecular level. For example, in the case of acetic acid dissolved in water and forming acetate and hydronium ions,
a proton may hop from one molecule of acetic acid onto a water molecule and then onto an acetate anion to form another molecule of acetic acid and leaving the number of acetic acid molecules unchanged. This is an example of dynamic equilibrium. Equilibria, like the rest of thermodynamics, are statistical phenomena, averages of microscopic behavior.
Le Châtelier's principle (1884) predicts the behavior of an equilibrium system when changes to its reaction conditions occur. If a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to partially reverse the change. For example, adding more S (to the chemical reaction above) from the outside will cause an excess of products, and the system will try to counteract this by increasing the reverse reaction and pushing the equilibrium point backward (though the equilibrium constant will stay the same).
If mineral acid is added to the acetic acid mixture, increasing the concentration of hydronium ion, the amount of dissociation must decrease as the reaction is driven to the left in accordance with this principle. This can also be deduced from the equilibrium constant expression for the reaction:
If {H3O+} increases {CH3CO2H} must increase and must decrease. The H2O is left out, as it is the solvent and its concentration remains high and nearly constant.
J. W. Gibbs suggested in 1873 that equilibrium is attained when the "available energy" (now known as Gibbs free energy or Gibbs energy) of the system is at its minimum value, assuming the reaction is carried out at a constant temperature and pressure. What this means is that the derivative of the Gibbs energy with respect to reaction coordinate (a measure of the extent of reaction that has occurred, ranging from zero for all reactants to a maximum for all products) vanishes (because dG = 0), signaling a stationary point. This derivative is called the reaction Gibbs energy (or energy change) and corresponds to the difference between the chemical potentials of reactants and products at the composition of the reaction mixture. This criterion is both necessary and sufficient. If a mixture is not at equilibrium, the liberation of the excess Gibbs energy (or Helmholtz energy at constant volume reactions) is the "driving force" for the composition of the mixture to change until equilibrium is reached. The equilibrium constant can be related to the standard Gibbs free energy change for the reaction by the equation
where R is the universal gas constant and T the temperature.
When the reactants are dissolved in a medium of high ionic strength the quotient of activity coefficients may be taken to be constant. In that case the concentration quotient, Kc,
where [A] is the concentration of A, etc., is independent of the analytical concentration of the reactants. For this reason, equilibrium constants for solutions are usually determined in media of high ionic strength. Kc varies with ionic strength, temperature and pressure (or volume). Likewise Kp for gases depends on partial pressure. These constants are easier to measure and encountered in high-school chemistry courses.
Thermodynamics
At constant temperature and pressure, one must consider the Gibbs free energy, G, while at constant temperature and volume, one must consider the Helmholtz free energy, A, for the reaction; and at constant internal energy and volume, one must consider the entropy, S, for the reaction.
The constant volume case is important in geochemistry and atmospheric chemistry where pressure variations are significant. Note that, if reactants and products were in standard state (completely pure), then there would be no reversibility and no equilibrium. Indeed, they would necessarily occupy disjoint volumes of space. The mixing of the products and reactants contributes a large entropy increase (known as entropy of mixing) to states containing equal mixture of products and reactants and gives rise to a distinctive minimum in the Gibbs energy as a function of the extent of reaction. The standard Gibbs energy change, together with the Gibbs energy of mixing, determine the equilibrium state.
In this article only the constant pressure case is considered. The relation between the Gibbs free energy and the equilibrium constant can be found by considering chemical potentials.
At constant temperature and pressure in the absence of an applied voltage, the Gibbs free energy, G, for the reaction depends only on the extent of reaction: ξ (Greek letter xi), and can only decrease according to the second law of thermodynamics. It means that the derivative of G with respect to ξ must be negative if the reaction happens; at the equilibrium this derivative is equal to zero.
:equilibrium
In order to meet the thermodynamic condition for equilibrium, the Gibbs energy must be stationary, meaning that the derivative of G with respect to the extent of reaction, ξ, must be zero. It can be shown that in this case, the sum of chemical potentials times the stoichiometric coefficients of the products is equal to the sum of those corresponding to the reactants. Therefore, the sum of the Gibbs energies of the reactants must be the equal to the sum of the Gibbs energies of the products.
where μ is in this case a partial molar Gibbs energy, a chemical potential. The chemical potential of a reagent A is a function of the activity, {A} of that reagent.
(where μ is the standard chemical potential).
The definition of the Gibbs energy equation interacts with the fundamental thermodynamic relation to produce
.
Inserting dNi = νi dξ into the above equation gives a stoichiometric coefficient () and a differential that denotes the reaction occurring to an infinitesimal extent (dξ). At constant pressure and temperature the above equations can be written as
which is the Gibbs free energy change for the reaction. This results in:
.
By substituting the chemical potentials:
,
the relationship becomes:
:
which is the standard Gibbs energy change for the reaction that can be calculated using thermodynamical tables.
The reaction quotient is defined as:
Therefore,
At equilibrium:
leading to:
and
Obtaining the value of the standard Gibbs energy change, allows the calculation of the equilibrium constant.
Addition of reactants or products
For a reactional system at equilibrium: Qr = Keq; ξ = ξeq.
If the activities of constituents are modified, the value of the reaction quotient changes and becomes different from the equilibrium constant: Qr ≠ Keq and then
If activity of a reagent i increases the reaction quotient decreases. Then and The reaction will shift to the right (i.e. in the forward direction, and thus more products will form).
If activity of a product j increases, then and The reaction will shift to the left (i.e. in the reverse direction, and thus less products will form).
Note that activities and equilibrium constants are dimensionless numbers.
Treatment of activity
The expression for the equilibrium constant can be rewritten as the product of a concentration quotient, Kc and an activity coefficient quotient, Γ.
[A] is the concentration of reagent A, etc. It is possible in principle to obtain values of the activity coefficients, γ. For solutions, equations such as the Debye–Hückel equation or extensions such as Davies equation Specific ion interaction theory or Pitzer equations may be used. However this is not always possible. It is common practice to assume that Γ is a constant, and to use the concentration quotient in place of the thermodynamic equilibrium constant. It is also general practice to use the term equilibrium constant instead of the more accurate concentration quotient. This practice will be followed here.
For reactions in the gas phase partial pressure is used in place of concentration and fugacity coefficient in place of activity coefficient. In the real world, for example, when making ammonia in industry, fugacity coefficients must be taken into account. Fugacity, f, is the product of partial pressure and fugacity coefficient. The chemical potential of a species in the real gas phase is given by
so the general expression defining an equilibrium constant is valid for both solution and gas phases.
Concentration quotients
In aqueous solution, equilibrium constants are usually determined in the presence of an "inert" electrolyte such as sodium nitrate, NaNO3, or potassium perchlorate, KClO4. The ionic strength of a solution is given by
where ci and zi stand for the concentration and ionic charge of ion type i, and the sum is taken over all the N types of charged species in solution. When the concentration of dissolved salt is much higher than the analytical concentrations of the reagents, the ions originating from the dissolved salt determine the ionic strength, and the ionic strength is effectively constant. Since activity coefficients depend on ionic strength, the activity coefficients of the species are effectively independent of concentration. Thus, the assumption that Γ is constant is justified. The concentration quotient is a simple multiple of the equilibrium constant.
However, Kc will vary with ionic strength. If it is measured at a series of different ionic strengths, the value can be extrapolated to zero ionic strength. The concentration quotient obtained in this manner is known, paradoxically, as a thermodynamic equilibrium constant.
Before using a published value of an equilibrium constant in conditions of ionic strength different from the conditions used in its determination, the value should be adjusted.
Metastable mixtures
A mixture may appear to have no tendency to change, though it is not at equilibrium. For example, a mixture of SO2 and O2 is metastable as there is a kinetic barrier to formation of the product, SO3.
2 SO2 + O2 2 SO3
The barrier can be overcome when a catalyst is also present in the mixture as in the contact process, but the catalyst does not affect the equilibrium concentrations.
Likewise, the formation of bicarbonate from carbon dioxide and water is very slow under normal conditions
but almost instantaneous in the presence of the catalytic enzyme carbonic anhydrase.
Pure substances
When pure substances (liquids or solids) are involved in equilibria their activities do not appear in the equilibrium constant because their numerical values are considered one.
Applying the general formula for an equilibrium constant to the specific case of a dilute solution of acetic acid in water one obtains
CH3CO2H + H2O CH3CO2− + H3O+
For all but very concentrated solutions, the water can be considered a "pure" liquid, and therefore it has an activity of one. The equilibrium constant expression is therefore usually written as
.
A particular case is the self-ionization of water
2 H2O H3O+ + OH−
Because water is the solvent, and has an activity of one, the self-ionization constant of water is defined as
It is perfectly legitimate to write [H+] for the hydronium ion concentration, since the state of solvation of the proton is constant (in dilute solutions) and so does not affect the equilibrium concentrations. Kw varies with variation in ionic strength and/or temperature.
The concentrations of H+ and OH− are not independent quantities. Most commonly [OH−] is replaced by Kw[H+]−1 in equilibrium constant expressions which would otherwise include hydroxide ion.
Solids also do not appear in the equilibrium constant expression, if they are considered to be pure and thus their activities taken to be one. An example is the Boudouard reaction:
2 CO CO2 + C
for which the equation (without solid carbon) is written as:
Multiple equilibria
Consider the case of a dibasic acid H2A. When dissolved in water, the mixture will contain H2A, HA− and A2−. This equilibrium can be split into two steps in each of which one proton is liberated.
K1 and K2 are examples of stepwise equilibrium constants. The overall equilibrium constant, βD, is product of the stepwise constants.
Note that these constants are dissociation constants because the products on the right hand side of the equilibrium expression are dissociation products. In many systems, it is preferable to use association constants.
β1 and β2 are examples of association constants. Clearly and ; and
For multiple equilibrium systems, also see: theory of Response reactions.
Effect of temperature
The effect of changing temperature on an equilibrium constant is given by the van 't Hoff equation
Thus, for exothermic reactions (ΔH is negative), K decreases with an increase in temperature, but, for endothermic reactions, (ΔH is positive) K increases with an increase temperature. An alternative formulation is
At first sight this appears to offer a means of obtaining the standard molar enthalpy of the reaction by studying the variation of K with temperature. In practice, however, the method is unreliable because error propagation almost always gives very large errors on the values calculated in this way.
Effect of electric and magnetic fields
The effect of electric field on equilibrium has been studied by Manfred Eigen among others.
Types of equilibrium
Equilibrium can be broadly classified as heterogeneous and homogeneous equilibrium. Homogeneous equilibrium consists of reactants and products belonging in the same phase whereas heterogeneous equilibrium comes into play for reactants and products in different phases.
In the gas phase: rocket engines
The industrial synthesis such as ammonia in the Haber–Bosch process (depicted right) takes place through a succession of equilibrium steps including adsorption processes
Atmospheric chemistry
Seawater and other natural waters: chemical oceanography
Distribution between two phases
log D distribution coefficient: important for pharmaceuticals where lipophilicity is a significant property of a drug
Liquid–liquid extraction, Ion exchange, Chromatography
Solubility product
Uptake and release of oxygen by hemoglobin in blood
Acid–base equilibria: acid dissociation constant, hydrolysis, buffer solutions, indicators, acid–base homeostasis
Metal–ligand complexation: sequestering agents, chelation therapy, MRI contrast reagents, Schlenk equilibrium
Adduct formation: host–guest chemistry, supramolecular chemistry, molecular recognition, dinitrogen tetroxide
In certain oscillating reactions, the approach to equilibrium is not asymptotically but in the form of a damped oscillation .
The related Nernst equation in electrochemistry gives the difference in electrode potential as a function of redox concentrations.
When molecules on each side of the equilibrium are able to further react irreversibly in secondary reactions, the final product ratio is determined according to the Curtin–Hammett principle.
In these applications, terms such as stability constant, formation constant, binding constant, affinity constant, association constant and dissociation constant are used. In biochemistry, it is common to give units for binding constants, which serve to define the concentration units used when the constant's value was determined.
Composition of a mixture
When the only equilibrium is that of the formation of a 1:1 adduct as the composition of a mixture, there are many ways that the composition of a mixture can be calculated. For example, see ICE table for a traditional method of calculating the pH of a solution of a weak acid.
There are three approaches to the general calculation of the composition of a mixture at equilibrium.
The most basic approach is to manipulate the various equilibrium constants until the desired concentrations are expressed in terms of measured equilibrium constants (equivalent to measuring chemical potentials) and initial conditions.
Minimize the Gibbs energy of the system.
Satisfy the equation of mass balance. The equations of mass balance are simply statements that demonstrate that the total concentration of each reactant must be constant by the law of conservation of mass.
Mass-balance equations
In general, the calculations are rather complicated or complex. For instance, in the case of a dibasic acid, H2A dissolved in water the two reactants can be specified as the conjugate base, A2−, and the proton, H+. The following equations of mass-balance could apply equally well to a base such as 1,2-diaminoethane, in which case the base itself is designated as the reactant A:
with TA the total concentration of species A. Note that it is customary to omit the ionic charges when writing and using these equations.
When the equilibrium constants are known and the total concentrations are specified there are two equations in two unknown "free concentrations" [A] and [H]. This follows from the fact that [HA] = β1[A][H], [H2A] = β2[A][H]2 and [OH] = Kw[H]−1
so the concentrations of the "complexes" are calculated from the free concentrations and the equilibrium constants.
General expressions applicable to all systems with two reagents, A and B would be
It is easy to see how this can be extended to three or more reagents.
Polybasic acids
The composition of solutions containing reactants A and H is easy to calculate as a function of p[H]. When [H] is known, the free concentration [A] is calculated from the mass-balance equation in A.
The diagram alongside, shows an example of the hydrolysis of the aluminium Lewis acid Al3+(aq) shows the species concentrations for a 5 × 10−6 M solution of an aluminium salt as a function of pH. Each concentration is shown as a percentage of the total aluminium.
Solution and precipitation
The diagram above illustrates the point that a precipitate that is not one of the main species in the solution equilibrium may be formed. At pH just below 5.5 the main species present in a 5 μM solution of Al3+ are aluminium hydroxides Al(OH)2+, and , but on raising the pH Al(OH)3 precipitates from the solution. This occurs because Al(OH)3 has a very large lattice energy. As the pH rises more and more Al(OH)3 comes out of solution. This is an example of Le Châtelier's principle in action: Increasing the concentration of the hydroxide ion causes more aluminium hydroxide to precipitate, which removes hydroxide from the solution. When the hydroxide concentration becomes sufficiently high the soluble aluminate, , is formed.
Another common instance where precipitation occurs is when a metal cation interacts with an anionic ligand to form an electrically neutral complex. If the complex is hydrophobic, it will precipitate out of water. This occurs with the nickel ion Ni2+ and dimethylglyoxime, (dmgH2): in this case the lattice energy of the solid is not particularly large, but it greatly exceeds the energy of solvation of the molecule Ni(dmgH)2.
Minimization of Gibbs energy
At equilibrium, at a specified temperature and pressure, and with no external forces, the Gibbs free energy G is at a minimum:
where μj is the chemical potential of molecular species j, and Nj is the amount of molecular species j. It may be expressed in terms of thermodynamic activity as:
where is the chemical potential in the standard state, R is the gas constant T is the absolute temperature, and Aj is the activity.
For a closed system, no particles may enter or leave, although they may combine in various ways. The total number of atoms of each element will remain constant. This means that the minimization above must be subjected to the constraints:
where aij is the number of atoms of element i in molecule j and b is the total number of atoms of element i, which is a constant, since the system is closed. If there are a total of k types of atoms in the system, then there will be k such equations. If ions are involved, an additional row is added to the aij matrix specifying the respective charge on each molecule which will sum to zero.
This is a standard problem in optimisation, known as constrained minimisation. The most common method of solving it is using the method of Lagrange multipliers (although other methods may be used).
Define:
where the λi are the Lagrange multipliers, one for each element. This allows each of the Nj and λj to be treated independently, and it can be shown using the tools of multivariate calculus that the equilibrium condition is given by
(For proof see Lagrange multipliers.) This is a set of (m + k) equations in (m + k) unknowns (the Nj and the λi) and may, therefore, be solved for the equilibrium concentrations Nj as long as the chemical activities are known as functions of the concentrations at the given temperature and pressure. (In the ideal case, activities are proportional to concentrations.) (See Thermodynamic databases for pure substances.) Note that the second equation is just the initial constraints for minimization.
This method of calculating equilibrium chemical concentrations is useful for systems with a large number of different molecules. The use of k atomic element conservation equations for the mass constraint is straightforward, and replaces the use of the stoichiometric coefficient equations. The results are consistent with those specified by chemical equations. For example, if equilibrium is specified by a single chemical equation:,
where νj is the stoichiometric coefficient for the j th molecule (negative for reactants, positive for products) and Rj is the symbol for the j th molecule, a properly balanced equation will obey:
Multiplying the first equilibrium condition by νj and using the above equation yields:
As above, defining ΔG
where Kc is the equilibrium constant, and ΔG will be zero at equilibrium.
Analogous procedures exist for the minimization of other thermodynamic potentials.
See also
Acidosis
Alkalosis
Arterial blood gas
Benesi–Hildebrand method
Determination of equilibrium constants
Equilibrium constant
Henderson–Hasselbalch equation
Mass-action ratio
Michaelis–Menten kinetics
pCO2
pH
pKa
Redox equilibria
Steady state (chemistry)
Thermodynamic databases for pure substances
Non-random two-liquid model (NRTL model) – Phase equilibrium calculations
UNIQUAC model – Phase equilibrium calculations
References
Further reading
Mainly concerned with gas-phase equilibria.
External links
Analytical chemistry
Physical chemistry | Chemical equilibrium | Physics,Chemistry | 5,214 |
15,806,009 | https://en.wikipedia.org/wiki/Informative%20site | In phylogenetics, informative site is a term used when maximum parsimony is the optimality criterion for construction of a phylogenetic tree. It refers to a characteristic for which the number of character-state evolutionary changes of at this site depends on the topology of the tree. The charactetistics can take on multiple types of data, including morphological (such as the presence of wings, tentacles, etc.) or molecular information such as sequences of DNA or proteins.
The informative site is a position in the relevant set of aligned sequences at which there are at least two different character states and each of those states occurs in at least two of the sequences. In other words, it cannot be a fully conserved (i.e., invariable) site nor can it be a (singleton) site with a difference in only one sequence (as seen, for example, in single-nucleotide polymorphisms and single-nucleotide variants). In both cases, the number of character-state changes is the same regardless of the topology of the tree, equal to 0 and 1 respectively.
References
Computational phylogenetics | Informative site | Chemistry,Biology | 230 |
1,197,184 | https://en.wikipedia.org/wiki/Formal%20proof | In logic and mathematics, a formal proof or derivation is a finite sequence of sentences (known as well-formed formulas when relating to formal language), each of which is an axiom, an assumption, or follows from the preceding sentences in the sequence, according to the rule of inference. It differs from a natural language argument in that it is rigorous, unambiguous and mechanically verifiable. If the set of assumptions is empty, then the last sentence in a formal proof is called a theorem of the formal system. The notion of theorem is generally effective, but there may be no method by which we can reliably find proof of a given sentence or determine that none exists. The concepts of Fitch-style proof, sequent calculus and natural deduction are generalizations of the concept of proof.
The theorem is a syntactic consequence of all the well-formed formulas preceding it in the proof. For a well-formed formula to qualify as part of a proof, it must be the result of applying a rule of the deductive apparatus (of some formal system) to the previous well-formed formulas in the proof sequence.
Formal proofs often are constructed with the help of computers in interactive theorem proving (e.g., through the use of proof checker and automated theorem prover). Significantly, these proofs can be checked automatically, also by computer. Checking formal proofs is usually simple, while the problem of finding proofs (automated theorem proving) is usually computationally intractable and/or only semi-decidable, depending upon the formal system in use.
Background
Formal language
A formal language is a set of finite sequences of symbols. Such a language can be defined without reference to any meanings of any of its expressions; it can exist before any interpretation is assigned to it – that is, before it has any meaning. Formal proofs are expressed in some formal languages.
Formal grammar
A formal grammar (also called formation rules) is a precise description of the well-formed formulas of a formal language. It is synonymous with the set of strings over the alphabet of the formal language which constitute well formed formulas. However, it does not describe their semantics (i.e. what they mean).
Formal systems
A formal system (also called a logical calculus, or a logical system) consists of a formal language together with a deductive apparatus (also called a deductive system). The deductive apparatus may consist of a set of transformation rules (also called inference rules) or a set of axioms, or have both. A formal system is used to derive one expression from one or more other expressions.
Interpretations
An interpretation of a formal system is the assignment of meanings to the symbols, and truth values to the sentences of a formal system. The study of interpretations is called formal semantics. Giving an interpretation is synonymous with ''constructing a model.
See also
Axiomatic system
Formal verification
Mathematical proof
Proof assistant
Proof calculus
Proof theory
Proof (truth)
De Bruijn factor
References
External links
2πix.com: Logic Part of a series of articles covering mathematics and logic.
Archive of Formal Proofs
Mizar Home Page
Pr∞fWiki, Definition:Proof System/Formal Proof
Formal languages
Proof theory
Formal systems
Syntax (logic)
Logical truth
de:Axiomatischer Beweis | Formal proof | Mathematics | 673 |
33,947,481 | https://en.wikipedia.org/wiki/List%20of%20%CE%B2-lactam%20antibiotics | This is a list of common β-lactam antibiotics—both administered drugs and those not in clinical use—organized by structural class. Antibiotics are listed alphabetically within their class or subclass by their nonproprietary name. If an antibiotic is a combination drug, both ingredients will be listed.
Penams
Narrow-spectrum
β-lactamase-sensitive
Benzathine
benzylpenicillin (Penicillin G)
Benzathine penicillin G
Benzathine penicillin V
Phenoxymethylpenicillin (penicillin V)
Procaine penicillin
Pheneticillin
β-lactamase-resistant
Cloxacillin
Dicloxacillin
Flucloxacillin
Methicillin
Nafcillin
Oxacillin
Temocillin
Broad spectrum
Amoxicillin
Ampicillin
Extended spectrum (Antipseudomonal)
Mecillinam
Piperacillin
Carbenicillin
Ticarcillin
Carboxypenicillins
Carbenicillin
Ticarcillin
Ureidopenicillins
Azlocillin
Mezlocillin
Piperacillin
Cephems
First generation (moderate spectrum)
Cefazolin
Cephalexin
Cephalosporin C
Cephalothin
Cefapirin
Second generation (moderate spectrum)
cefuroxime, cefaclor, cefprozil
With anti-Haemophilus activity
Cefaclor
Cefamandole
Cefuroxime
With anti-anaerobic activity
Cefotetan
Cefoxitin
Third generation (broad spectrum)
Cefixime
Cefotaxime
Cefpodoxime
Ceftazidime
Ceftriaxone
Cefdinir
Fourth generation (broad spectrum)
(With β-lactamase stability and enhanced activity against Gram-positive bacteria and Pseudomonas aeruginosa)
Cefepime
Cefpirome
Fifth generation* (broad spectrum)
(activity against MRSA and variably VRE. *Not universally accepted nomenclature. NO Antipseudomonal activity, mostly ceftriaxone coverage with additional MRSA and some VRE)
Ceftaroline, Ceftobiprole
Carbapenems and penems
(Broadest spectrum of β-lactam antibiotics)
Biapenem
Doripenem
Ertapenem
Faropenem
Imipenem
Meropenem
Panipenem
Razupenem
Tebipenem
Thienamycin
Monobactams
Aztreonam
Tigemonam
Nocardicin A
Tabtoxinine β-lactam (does not inhibit penicillin-binding proteins)
β-lactamase inhibitors
Clavulanic acid
Tazobactam
Sulbactam
Avibactam
Beta-lactam antibiotics
Beta-lactam antibiotics | List of β-lactam antibiotics | Chemistry | 584 |
39,334,096 | https://en.wikipedia.org/wiki/World%20manifold | In gravitation theory, a world manifold endowed with some Lorentzian pseudo-Riemannian metric and an associated space-time structure is a space-time. Gravitation theory is formulated as classical field theory on natural bundles over a world manifold.
Topology
A world manifold is a four-dimensional orientable real smooth manifold. It is assumed to be a Hausdorff and second countable topological space. Consequently, it is a locally compact space which is a union of a countable number of compact subsets, a separable space, a paracompact and completely regular space. Being paracompact, a world manifold admits a partition of unity by smooth functions. Paracompactness is an essential characteristic of a world manifold. It is necessary and sufficient in order that a world manifold admits a Riemannian metric and necessary for the existence of a pseudo-Riemannian metric. A world manifold is assumed to be connected and, consequently, it is arcwise connected.
Riemannian structure
The tangent bundle of a world manifold and the associated principal frame bundle of linear tangent frames in possess a general linear group structure group . A world manifold is said to be parallelizable if the tangent bundle and, accordingly, the frame bundle are trivial, i.e., there exists a global section (a frame field) of . It is essential that the tangent and associated bundles over a world manifold admit a bundle atlas of finite number of trivialization charts.
Tangent and frame bundles over a world manifold are natural bundles characterized by general covariant transformations. These transformations are gauge symmetries of gravitation theory on a world manifold.
By virtue of the well-known theorem on structure group reduction, a structure group of a frame bundle over a world manifold is always reducible to its maximal compact subgroup . The corresponding global section of the quotient bundle is a Riemannian metric on . Thus, a world manifold always admits a Riemannian metric which makes a metric topological space.
Lorentzian structure
In accordance with the geometric Equivalence Principle, a world manifold possesses a Lorentzian structure, i.e., a structure group of a frame bundle must be reduced to a Lorentz group . The corresponding global section of the quotient bundle is a pseudo-Riemannian metric of signature on . It is treated as a gravitational field in General Relativity and as a classical Higgs field in gauge gravitation theory.
A Lorentzian structure need not exist. Therefore, a world manifold is assumed to satisfy a certain topological condition. It is either a noncompact topological space or a compact space with a zero Euler characteristic. Usually, one also requires that a world manifold admits a spinor structure in order to describe Dirac fermion fields in gravitation theory. There is the additional topological obstruction to the existence of this structure. In particular, a noncompact world manifold must be parallelizable.
Space-time structure
If a structure group of a frame bundle is reducible to a Lorentz group, the latter is always reducible to its maximal compact subgroup . Thus, there is the commutative diagram
of the reduction of structure groups of a frame bundle in
gravitation theory. This reduction diagram results in the following.
(i) In gravitation theory on a world manifold , one can always choose an atlas of a frame bundle (characterized by local frame fields ) with -valued transition functions. These transition functions preserve a time-like component of local frame fields which, therefore, is globally defined. It is a nowhere vanishing vector field on . Accordingly, the dual time-like covector field also is globally defined, and it yields a spatial distribution
on such that . Then the tangent bundle of a world manifold admits a space-time decomposition
, where is a one-dimensional fibre bundle spanned by a time-like vector field . This decomposition, is called the -compatible space-time structure. It makes a world manifold the space-time.
(ii) Given the above-mentioned diagram of reduction of structure groups, let and be the corresponding
pseudo-Riemannian and Riemannian metrics on . They form a triple obeying the relation
.
Conversely, let a world manifold admit a nowhere vanishing
one-form (or, equivalently, a nowhere vanishing vector
field). Then any Riemannian metric on yields the
pseudo-Riemannian metric
.
It follows that a world manifold admits a pseudo-Riemannian
metric if and only if there exists a nowhere vanishing vector (or covector) field on .
Let us note that a -compatible Riemannian metric in a triple defines a -compatible distance function on a world manifold . Such a function brings into a metric space whose locally Euclidean topology is equivalent to a manifold topology on . Given a gravitational field , the -compatible Riemannian metrics and the corresponding distance
functions are different for different spatial distributions
and . It follows that physical observers associated with
these different spatial distributions perceive a world manifold as different Riemannian spaces. The well-known relativistic changes of sizes of moving bodies exemplify this phenomenon.
However, one attempts to derive a world topology directly from a space-time structure (a path topology, an Alexandrov topology). If a space-time satisfies the strong causality condition, such topologies coincide with a familiar manifold topology of a world manifold. In a general case, they however are rather extraordinary.
Causality conditions
A space-time structure is called integrable if a spatial distribution is involutive. In this case, its integral manifolds constitute a spatial foliation of a world manifold whose leaves are spatial three-dimensional subspaces. A spatial foliation is called causal if no curve transversal to its leaves intersects each leave more than once. This condition is equivalent to the stable causality of Stephen Hawking. A space-time foliation is causal if and only if it is a foliation of level surfaces of some smooth real function on whose differential nowhere vanishes. Such a foliation is a fibred manifold .
However, this is not the case of a compact world manifold which can not be
a fibred manifold over .
The stable causality does not provide the simplest causal structure. If a fibred manifold is a fibre bundle, it is trivial, i.e., a world manifold is a globally hyperbolic manifold . Since any oriented three-dimensional manifold is parallelizable, a globally
hyperbolic world manifold is parallelizable.
See also
Spacetime
Mathematics of general relativity
Gauge gravitation theory
References
S.W. Hawking, G.F.R. Ellis, The Large Scale Structure of Space-Time (Cambridge Univ. Press, Cambridge, 1973)
C.T.G. Dodson, Categories, Bundles, and Spacetime Topology (Shiva Publ. Ltd., Orpington, UK, 1980)
External links
Gravity
Theoretical physics | World manifold | Physics | 1,413 |
13,337,084 | https://en.wikipedia.org/wiki/Nanomesh | The nanomesh is an inorganic nanostructured two-dimensional material, similar to graphene. It was discovered in 2003 at the University of Zurich, Switzerland.
It consists of a single layer of boron (B) and nitrogen (N) atoms, which forms by self-assembly into a highly regular mesh after high-temperature exposure of a clean rhodium or ruthenium surface to borazine under ultra-high vacuum.
The nanomesh looks like an assembly of hexagonal pores (see right image) at the nanometer (nm) scale. The distance between two pore centers is only 3.2 nm, whereas each pore has a diameter of about 2 nm and is 0.05 nm deep. The lowest regions bind strongly to the underlying metal, while the wires (highest regions) are only bound to the surface through strong cohesive forces within the layer itself.
The boron nitride nanomesh is not only stable under vacuum, air and some liquids, but also up to temperatures of 796 °C (1070 K). In addition it shows the extraordinary ability to trap molecules and metallic clusters, which have similar sizes to the nanomesh pores, forming a well-ordered array. These characteristics may provide applications of the material in areas like, surface functionalisation, spintronics, quantum computing and data storage media like hard drives.
Structure
h-BN nanomesh is a single sheet of hexagonal boron nitride, which forms on substrates like rhodium Rh(111) or ruthenium Ru(0001) crystals by a self-assembly process.
The unit cell of the h-BN nanomesh consists of 13x13 BN or 12x12 Rh atoms with a lattice constant of 3.2 nm. In a cross-section it means that 13 boron or nitrogen atoms are sitting on 12 rhodium atoms. This implies a modification of the relative positions of each BN towards the substrate atoms within a unit cell, where some bonds are more attractive or repulsive than other (site selective bonding), what induces the corrugation of the nanomesh (see right image with pores and wires).
The nanomesh corrugation amplitude of 0.05 nm causes a strong effect on the electronic structure, where two distinct BN regions are observed. They are easily recognized in the lower right image, which is a scanning tunneling microscopy (STM) measurement, as well as in the lower left image representing a theoretical calculation of the same area. A strongly bounded region assigned to the pores is visible in blue in the left image below (center of bright rings in the right image) and a weakly bound region assigned to the wires appears yellow-red in the left image below (area in-between rings in the right image).
See for more details.
Properties
The nanomesh is stable under a wide range of environments like air, water and electrolytes among others. It is also temperature resistant since it does not decompose in temperatures up to 1275K under a vacuum. In addition to these exceptional stabilities, the nanomesh shows the extraordinary ability to act as a scaffold for metallic nanoclusters and to trap molecules forming a well-ordered array.
In the case of gold (Au), its evaporation on the nanomesh leads to formation of well-defined round Au nanoparticles, which are centered at the nanomesh pores.
The STM figure on the right shows Naphthalocyanine (Nc) molecules, which were vapor-deposited onto the nanomesh. These planar molecules have a diameter of about 2 nm, whose size is comparable to that of the nanomesh pores (see upper inset). It is spectacularly visible how the molecules form a well-ordered array with the periodicity of the nanomesh (3.22 nm). The lower inset shows a region of this substrate with higher resolution, where individual molecules are trapped inside the pores. In addition, the molecules seem to keep their native conformation, what means that their functionality is kept, which is nowadays a challenge in nanoscience.
Such systems with wide spacing between individual molecules/clusters and negligible intermolecular interactions might be interesting for applications such as molecular electronics and memory elements, in photochemistry or in optical devices.
See for more detailed information.
Preparation and analysis
Well-ordered nanomeshes are grown by thermal decomposition of borazine (HBNH)3, a colorless substance that is liquid at room temperature. The nanomesh results after exposing the atomically clean Rh(111) or Ru(0001) surface to borazine by chemical vapor deposition (CVD).
The substrate is kept at a temperature of 796 °C (1070 K) when borazine is introduced in the vacuum chamber at a dose of about 40 L (1 Langmuir = 10−6 torr sec). A typical borazine vapor pressure inside the ultrahigh vacuum chamber during the exposure is 3x10−7 mbar.
After cooling down to room temperature, the regular mesh structure is observed using different experimental techniques. Scanning tunneling microscopy (STM) gives a direct look on the local real space structure of the nanomesh, while low energy electron diffraction (LEED) gives information about the surface structures ordered over the whole sample. Ultraviolet photoelectron spectroscopy (UPS) gives information about the electronic states in the outermost atomic layers of a sample, i.e. electronic information of the top substrate layers and the nanomesh.
See also
Other forms
CVD of borazine on other substrates has not led so far to the formation of a corrugated nanomesh. A flat BN layer is observed on nickel and palladium, whereas stripped structures appear on molybdenum instead.
References and notes
Other links
http://www.nanomesh.ch
http://www.nanomesh.org
Two-dimensional nanomaterials
Self-organization
Thin films
Nitrides
Boron compounds
III-V compounds
Transition metals
NASA spin-off technologies | Nanomesh | Chemistry,Materials_science,Mathematics,Engineering | 1,274 |
56,538,024 | https://en.wikipedia.org/wiki/Columbia%20Data%20Center | Columbia Data Center is Microsoft's data center in Quincy, Washington. Property at Quincy was purchased in 2006; the building opened in April, 2007; and the data center reached operational status in May, 2007. It was said to be the largest data center in the world as of 2015. The company located there due to low land costs, abundant data fiber, and extremely low cost electricity provided by Grant County PUD for as little as 1.9 or 2.5 cents per kilowatt-hour. Building began with a facility in 2006 and several expansions followed, occupying with of floorspace in two buildings on a complex by 2016.
The data center consumed 30 to 50 megawatts in 2012 and employs 50 people.
References
Buildings and structures in Grant County, Washington
Data centers
Microsoft buildings and structures
2007 establishments in Washington (state)
Infrastructure completed in 2007 | Columbia Data Center | Technology | 174 |
1,965,869 | https://en.wikipedia.org/wiki/Banks%E2%80%93Zaks%20fixed%20point | In quantum chromodynamics (and also N = 1 super quantum chromodynamics) with massless flavors, if the number of flavors, Nf, is sufficiently small (i.e. small enough to guarantee asymptotic freedom, depending on the number of colors), the theory can flow to an interacting conformal fixed point of the renormalization group. If the value of the coupling at that point is less than one (i.e. one can perform perturbation theory in weak coupling), then the fixed point is called a Banks–Zaks fixed point. The existence of the fixed point was first reported in 1974 by Belavin and Migdal and by Caswell, and later used by Banks and Zaks in their analysis of the phase structure of vector-like gauge theories with massless fermions. The name Caswell–Banks–Zaks fixed point is also used.
More specifically, suppose that we find that the beta function of a theory up to two loops has the form
where and are positive constants. Then there exists a value such that :
If we can arrange to be smaller than , then we have . It follows that when the theory flows to the IR it is a conformal, weakly coupled theory with coupling .
For the case of a non-Abelian gauge theory with gauge group and Dirac fermions in the fundamental representation of the gauge group for the flavored particles we have
where is the number of colors and the number of flavors. Then should lie just below in order for the Banks–Zaks fixed point to appear. Note that this fixed point only occurs if, in addition to the previous requirement on (which guarantees asymptotic freedom),
where the lower bound comes from requiring . This way remains positive while is still negative (see first equation in article) and one can solve with real solutions for . The coefficient was first correctly computed by Caswell, while the earlier paper by Belavin and Migdal has a wrong answer.
See also
Beta function
References
T. J. Hollowood, "Renormalization Group and Fixed Points in Quantum Field Theory", Springer, 2013, .
Gauge theories
Quantum chromodynamics
Fixed points (mathematics)
Renormalization group
Conformal field theory
Supersymmetric quantum field theory | Banks–Zaks fixed point | Physics,Mathematics | 468 |
3,157,586 | https://en.wikipedia.org/wiki/Dimethyl%20methylphosphonate | Dimethyl methylphosphonate is an organophosphorus compound with the chemical formula CH3PO(OCH3)2. It is a colourless liquid, which is primarily used as a flame retardant.
Synthesis
Dimethyl methylphosphonate can be prepared from trimethyl phosphite and a halomethane (e.g. iodomethane) via the Michaelis–Arbuzov reaction.
Dimethyl methylphosphonate is a schedule 2 chemical as it may be used in the production of chemical weapons. It will react with thionyl chloride to produce methylphosphonic acid dichloride, which is used in the production of sarin and soman nerve agents. Various amines can be used to catalyse this process. It can be used as a sarin-simulant for the calibration of organophosphorus detectors.
Uses
The primary commercial use of dimethyl methylphosphonate is as a flame retardant. Other commercial uses are a preignition additive for gasoline, anti-foaming agent, plasticizer, stabilizer, textile conditioner, antistatic agent, and an additive for solvents and low-temperature hydraulic fluids. It can be used as a catalyst and a reagent in organic synthesis, as it can generate a highly reactive ylide. The yearly production in the United States varies between .
About 190 liters of dimethyl methylphosphonate, together with other chemicals, were released during the crash of El Al Flight 1862 at Bijlmer in Amsterdam in 1992.
References
Methyl esters
Phosphonate esters
Flame retardants
Plasticizers
Chemical weapons
Antistatic agents
Fuel additives
Nerve agent precursors | Dimethyl methylphosphonate | Chemistry,Biology | 364 |
41,460,633 | https://en.wikipedia.org/wiki/Siguazodan | Siguazodan is a phosphodiesterase inhibitor.
References
Cyanamides
Guanidines
Phosphodiesterase inhibitors | Siguazodan | Chemistry | 32 |
1,013,492 | https://en.wikipedia.org/wiki/Marcos%20Moshinsky | Marcos Moshinsky Borodiansky (; ; 1921–2009) was a Mexican physicist of Ukrainian-Jewish origin whose work in the field of elementary particles won him the Prince of Asturias Prize for Scientific and Technical Investigation in 1988 and the UNESCO Science Prize in 1997.
Early life
He was born in 1921 into a Jewish family in Kyiv, Ukrainian SSR. At the age of three, he emigrated as a refugee to Mexico, where he became a naturalized citizen in 1942. He received a bachelor's degree in physics from the National Autonomous University of Mexico (UNAM) and a doctorate in the same discipline at Princeton University under Nobel Laureate Eugene Paul Wigner.
Career
In the 1950s he researched nuclear reactions and the structure of the atomic nucleus, introducing the concept of the transformation bracket for eigenstates of the quantum harmonic oscillator, which, together with the tables elaborated in collaboration with Thomas A. Brody, simplified calculations in the nuclear shell model and became an indispensable reference for the study of nuclear structure. In 1952, his work on the transient dynamics of matter waves led to the discovery of diffraction in time.
After completing postdoctoral studies at the Henri Poincaré Institute in Paris, France, he returned to Mexico City to serve as a professor at the UNAM. In 1967 he was chosen president of the Mexican Society of Physics and in 1972 he was admitted to the National College. He was the editor of several international scientific reviews, including the Bulletin of the Atomic Scientists, and authored four books and more than 200 technical papers. He received the Mexican National Prize for Science (1968), the Luis Elizondo Prize (1971), the Prince of Asturias Prize for Scientific and Technical Investigation (1988) and the UNESCO Science Prize (1997).
In 1990 he was elected a Fellow of the American Physical Society "for his many fundamental contributions to the description of many-body quantum systems through the use of group-theoretical techniques"
While practicing physics, he wrote a weekly column in the newspaper Excélsior on Mexican politics.
References
This article began as a translation of the corresponding article in the Spanish-language Wikipedia.
M. Moshinsky and Y. F. Smirnov, The harmonic oscillator in modern physics, Informa HealthCare, Amsterdam 1996.
External links
Profile at the Prince of Asturias Foundation
Profile at the National College of Mexico.
2009 deaths
1921 births
Scientists from Mexico City
UNESCO Science Prize laureates
Members of El Colegio Nacional (Mexico)
Particle physicists
20th-century Mexican physicists
Members of the Pontifical Academy of Sciences
Members of the Brazilian Academy of Sciences
National Autonomous University of Mexico alumni
Academic staff of the National Autonomous University of Mexico
Mexican people of Ukrainian-Jewish descent
Ukrainian Jews
Soviet emigrants to Mexico
Members of the Mexican Academy of Sciences
Mathematical physicists
Fellows of the American Physical Society | Marcos Moshinsky | Physics | 569 |
14,325,287 | https://en.wikipedia.org/wiki/Bluebugging | Bluebugging is a form of Bluetooth attack often caused by a lack of awareness. It was developed after the onset of bluejacking and bluesnarfing. Similar to bluesnarfing, bluebugging accesses and uses all phone features but is limited by the transmitting power of class 2 Bluetooth radios, normally capping its range at 10–15 meters. However, the operational range can be increased with the use of a directional antenna.
History
Bluebugging was developed by the German researcher Martin Herfurt in 2004, one year after the advent of bluejacking. Initially a threat against laptops with Bluetooth capability, it later targeted mobile phones and PDAs.
Bluebugging manipulates a target phone into compromising its security, this to create a backdoor attack before returning control of the phone to its owner. Once control of a phone has been established, it is used to call back the hacker who is then able to listen in to conversations, hence the name "bugging". The Bluebug program also has the capability to create a call forwarding application whereby the hacker receives calls intended for the target phone.
A further development of Bluebugging has allowed for the control of target phones through Bluetooth phone headsets, It achieves this by pretending to be the headset and thereby "tricking" the phone into obeying call commands. Not only can a hacker receive calls intended for the target phone, they can send messages, read phonebooks, and examine calendars.
See also
IEEE 802.15
Near-field communication
Personal area network
References
External links
Bluetooth Special Interest Group Site (includes specifications)
Official Bluetooth site aimed at users
Bluetooth/Ethernet Vendor MAC Address Lookup
Bluebugging Video and description
Bluetooth
Hacking (computer security) | Bluebugging | Technology | 362 |
27,603,257 | https://en.wikipedia.org/wiki/Kisrhombille | In geometry, a kisrhombille is a uniform tiling of rhombic faces, divided by central points into four triangles.
Examples:
3-6 kisrhombille – Euclidean plane
3-7 kisrhombille – hyperbolic plane
3-8 kisrhombille – hyperbolic plane
4-5 kisrhombille – hyperbolic plane
References
Uniform tilings
John Horton Conway | Kisrhombille | Physics | 86 |
50,204,361 | https://en.wikipedia.org/wiki/Potassium%20transporter%20family | The K+ Transporter (Trk) Family is a member of the voltage-gated ion channel (VIC) superfamily. The proteins of the Trk family are derived from Gram-negative and Gram-positive bacteria, yeast and plants.
Homology
The phylogenetic tree reveals that the proteins cluster according to phylogeny of the source organism with
the Gram-negative bacterial Trk proteins,
the Gram-negative and Gram-positive bacterial Ktr proteins,
the yeast proteins and
the plant proteins comprising four distinct clusters.
S. cerevisiae possesses at least two paralogues, high- and low-affinity K+ transporters. Folding pattern seen in Trk proteins resembles quadruplicated primitive K+ channels of the VIC superfamily (TC #1.A.1) instead of typical 12 TMS carriers. Homology has been established between Trk carriers and VIC family channels.
Structure
The sizes of the Trk family members vary from 423 residues to 1235 residues. The bacterial proteins are of 423-558 residues, the Triticum aestivum protein is 533 residues, and the yeast proteins vary between 841 and 1241 residues. These proteins possess 8 putative transmembrane α-helical spanners (TMSs). An 8 TMS topology with N- and C-termini on the inside, has been established for AtHKT1 of A. thaliana. and Trk2 of S. cerevisiae. This folding pattern resembles quadruplicated primitive K+ channels of the VIC superfamily (TC #1.A.1) instead of typical 12 TMS carriers. As homology has been established between Trk carriers and VIC family channels.
Function
Trk family members regulate various K+ transporters in all three domains of life. These regulatory subunits are generally called K+ transport/nucleotide binding subunits. TrkA domains can bind NAD+ and NADH, possibly allowing K+ transporters to be responsive to the redox state of the cell. The ratio of NADH/NAD+ may control gating. Multiple crystal structures of two KTN domains complexed with NAD+ or NADH reveal that these ligands control the oligomeric (tetrameric) state of KTN. The results suggest that KTN is inherently flexible, undergoing a large conformational change through a hinge motion. The KTN domains of Kef channels interact dynamically with the transporter. The KTN conformation then controls permease activity.
Both yeast transport systems are believed to function by K+:H+ symport, but the wheat protein functions by K+:Na+ symport. It is possible that some of these proteins can function by a channel-type mechanism. Positively charged residues in TMS8 of several ktr/Trk/HKT transporters probably face the channel and block a conformational change that is essential for channel activity while allowing secondary active transport.
The putative generalized transport reaction catalyzed by the Trk family members is:K+ (out) + H+ (out) ⇌ K+ (in) + H+ (in).
References
Protein families
Membrane proteins
Transmembrane proteins
Transmembrane transporters
Transport proteins
Integral membrane proteins | Potassium transporter family | Biology | 679 |
1,869,960 | https://en.wikipedia.org/wiki/Alazan%20%28rocket%29 | The Alazan rocket was a Cold War-era, 82mm Soviet rocket originally developed to distribute cloud seeding chemicals such as potassium or silver iodide. Some were converted into improvised munitions and modified to carry explosive warheads. Others were retrofitted with a warhead, which, in one case, contained up to 400g of radioactive caesium-137 and strontium-90. Both types were acquired by militants following the Soviet collapse.
References
Rockets and missiles | Alazan (rocket) | Astronomy | 98 |
8,310,995 | https://en.wikipedia.org/wiki/Shrinking%20city | Shrinking cities or urban depopulation are dense cities that have experienced a notable population loss. Emigration is a common reason for city shrinkage. Since the infrastructure of such cities was built to support a larger population, its maintenance can become a serious concern. A related phenomenon is counterurbanization.
Definition
Origins
The phenomenon of shrinking cities generally refers to a metropolitan area that experiences significant population loss in a short period of time. The process is also known as counterurbanization, metropolitan deconcentration, and metropolitan turnaround. It was popularized in reference to Eastern Europe post-socialism, when old industrial regions came under Western privatization and capitalism. Shrinking cities in the United States, on the other hand, have been forming since 2006 in dense urban centers while external suburban areas continue to grow. Suburbanization in tandem with deindustrialization, human migration, and the 2008 Great Recession all contribute to origins of shrinking cities in the U.S. Scholars estimate that one in six to one in four cities worldwide are shrinking in countries with expanding economies and those with deindustrialization. However, there are some issues with the concept of shrinking cities, as it seeks to group together areas that undergo depopulation for a variety of complex reasons. These may include an aging population, shifting industries, intentional shrinkage to improve quality of life, or a transitional phase, all of which require different responses and plans.
Causes
There are various theoretical explanations for the shrinking city phenomenon. Hollander et al. and Glazer cite railroads in port cities, the depreciation of national infrastructure (i.e., highways), and suburbanization as possible causes of de-urbanization. Pallagst also suggests that shrinkage is a response to deindustrialization, as jobs move from the city core to cheaper land on the periphery. This case has been observed in Detroit, where employment opportunities in the automobile industry were moved to the suburbs because of room for expansion and cheaper acreage. Bontje proposes three factors contributing to urban shrinkage, followed by one suggested by Hollander:
Urban development model: Based on the Fordist model of industrialization, it suggests that urbanization is a cyclical process and that urban and regional decline will eventually allow for increased growth
One company town/monostructure model: Cities that focus too much on one branch of economic growth make themselves vulnerable to rapid declines, such as the case with the automobile industry in Flint.
Shock therapy model: Especially in Eastern Europe post-socialism, state-owned companies did not survive privatization, leading to plant closures and massive unemployment.
Smart decline: City planners have utilized this term and inadvertently encouraged decline by "planning for less—fewer people, fewer buildings, fewer land uses.". It is a development method focused on improving the quality of life for current residents without taking those residents' needs into account, thus pushing more people out of the city core.
Effects
Economic
The shrinking of urban populations indicates a changing of economic and planning conditions of a city. Cities begin to 'shrink' from economic decline, usually resulting from war, debt, or lack of production and work force. Population decline affects a large number of communities, both communities that are far removed from and deep within large urban centers. These communities usually consist of native people and long-term residents, so the initial population is not large. The outflow of people is then detrimental to the production potential and quality of life in these regions, and a decline in employment and productivity ensues.
Social and infrastructural
Shrinking cities experience dramatic social changes due to fertility decline, changes in life expectancy, population aging, and household structure. Another reason for this shift is job-driven migration. This causes different household demands, posing a challenge to the urban housing market and the development of new land or urban planning. A decline in population does not inspire confidence in a city, and often deteriorates municipal morale. Coupled with a weak economy, the city and its infrastructure begin to deteriorate from lack of upkeep from citizens.
Political
Historically, shrinking cities have been a taboo topic in politics. Representatives ignored the problem and refused to deal with it, leading many to believe it was not a real problem. Today, urban shrinkage is an acknowledged issue, with many urban planning firms working together to strategize how to combat the implications that affect all dimensions of daily life.
International perspectives
Former Socialist regions in Europe and Central Asia have historically suffered the most from population decline and deindustrialization. East German cities, as well as former Yugoslavian and Soviet territories, were significantly affected by their weak economic situation after the fall of socialism. The reunification of European countries yielded both benefits and drawbacks. German cities like Leipzig and Dresden, for example, experienced a drastic population decline as many people emigrated to western cities like Berlin. Hamburg in particular experienced a population boom with record production yields in 1991, after the unification of Germany. Conversely, Leipzig and Dresden suffered from a failing economy and a neglected infrastructure. These cities were built to support a much larger population. However, both Dresden and Leipzig are now growing again, largely at the expense of smaller cities and rural areas. Shrinking cities in the United States face different issues, with much of the population migrating out of cities to other states for better economic opportunities and safer conditions. Advanced capitalist countries generally have a larger population, so this shift is not as dangerous as it is to post-socialist countries. The United States also has more firms willing to rehabilitate shrinking cities and invest in revitalization efforts. For example, after the 1989 Loma Prieta earthquake in San Francisco in 1989, the dynamics between the city and its residents provoked change and plans achieved visible improvements in the city. By contrast, cities in Germany have not gotten the same attention. Urban planning projects take a long time to be approved and established. As of now, Leipzig is taking steps toward making the city more nature-oriented and 'green' so that the population can be first stabilized, and then the country can focus on drawing the population back into the city.
Theories
The observable demographic out-migration and disinvestment of capital from many industrial cities across the globe following World War II prompted an academic investigation into the causes of shrinking cities, or urban decline. Serious issues of justice, racism, economic and health disparity, as well as inequitable power relations, are consequences of the shrinking cities phenomenon. The question is, what causes urban decline and why? While theories do vary, three main categories of influence are widely attributed to urban decline: deindustrialization, globalization, and suburbanization.
Deindustrialization
One theory of shrinking cities is deindustrialization or, the process of disinvestment from industrial urban centers. This theory of shrinking cities is mainly focused on post-World War II Europe as manufacturing declined in Western Europe and increased in the United States, causing a shift of global economic power to the United States. The result was that Western European industrialization largely ceased, and alternative industries arose. This economic shift is clearly seen through the United Kingdom's rise of a service sector economy. With the decline in industry, many jobs were lost or outsourced, resulting in urban decline and massive demographic movement from former industrial urban centers into suburban and rural locales.
Post-World War II politics
Rapid privatization incentives encouraged under the United States-sponsored post-World War II economic aid policies such as the Marshall Plan and Lend-Lease program, motivated free-market, capitalist approaches to governance across the Western European economic landscape. The result of these privatization schemes was a movement of capital into American manufacturing and financial markets and out of Western European industrial centers. American loans were also used as political currency contingent upon global investment schemes meant to stifle economic development within the Soviet-allied Eastern Bloc. With extensive debt tying capitalist Europe to the United States and financial blockades inhibiting full development of the communist Eastern half, this Cold War economic power structure greatly contributed to European urban decline.
The case of Great Britain
Great Britain, widely considered the first nation to fully industrialize, is often used as a case study in support of the theory of deindustrialization and urban decline. Political economists often point to the Cold War era as the moment when a monumental shift in global economic power structures occurred. The former "Great Empire" of the United Kingdom was built from industry, trade and financial dominion. This control was, however, effectively lost to the United States under such programs as the Lend-Lease and Marshall Plan. As the global financial market moved from London to New York City, so too did the influence of capital and investment.
With the initial decades following World War II dedicated to rebuilding or, readjusting the economic, political and cultural role of Britain within the new world order, it was not until the 1960s and 1970s that major concerns over urban decline emerged. With industry moving out of Western Europe and into the United States, rapid depopulation of cities and movement into rural areas occurred in Great Britain. Deindustrialization was advanced further under the Thatcherite privatization policies of the 1980s. Privatization of industry took away all remaining state protection of manufacturing. With industry now under private ownership, "free-market" incentives (along with a strong pound resulting from North Sea Oil) pushed further movement of manufacturing out of the United Kingdom.
Under Prime Minister Tony Blair, the United Kingdom effectively tried to revamp depopulated and unemployed cities through the enlargement of service sector industry. This shift from manufacturing to services did not, however, reverse the trend of urban decline observed beginning in 1966, with the exception of London.
The case of Leipzig
Leipzig serves as an example of urban decline on the Eastern half of post-World War II Europe. Leipzig, an East German city under Soviet domain during the Cold War era, did not receive adequate government investment as well as market outlets for its industrial goods. With the stagnation of demand for production, Leipzig began to deindustrialize as the investment in manufacturing stifled. This deindustrialization, demographers theorize, prompted populations to migrate from the city center and into the country and growing suburbs in order to find work elsewhere. Since the 2000s, Leipzig has re-industrialized and is once again a growing urban realm.
The case of Detroit
Although most major research on deindustrialization focuses on post-World War II Europe, many theorists also turn to the case of Detroit, Michigan as further evidence of the correlation between deindustrialization and shrinking cities. Detroit, nicknamed Motor City because of its expansive automobile manufacturing sector, reached its population peak during the 1950s. As European and Japanese industry recovered from the destruction of World War II, the American automobile industry no longer had a monopoly advantage. With new global market competition, Detroit began to lose its unrivaled position as "Motor City". With this falling demand, investment shifted to other locations outside of Detroit. Deindustrialization followed as production rates began to drop.
Globalization
As evident from the theory of deindustrialization, political economists and demographers both place huge importance on the global flows of capital and investment in relation to population stability. Many theorists point to the Bretton Woods Conference as setting the stage for a new globalized age of trade and investment. With the creation of the International Monetary Fund (IMF) and World Bank in addition to the United States' economic aid programs (i.e., Marshall Plan and Lend-Lease), many academics highlight Bretton Woods as a turning point in world economic relations. Under a new academic stratification of developed and developing nations, trends in capital investment flows and urban population densities were theorized following post-World War II global financial reorganization.
Product life-cycle theory
The product life-cycle theory was originally developed by Raymond Vernon to help improve the theoretical understanding of modern patterns of international trade. In a widely cited study by Jurgen Friedrichs, "A Theory of Urban Decline: Economy, Demography and Political Elites," Friedrichs aims to clarify and build upon the existing theory of product life-cycle in relation to urban decline. Accepting the premise of shrinking cities as result of economic decline and urban out-migration, Friedrichs discusses how and why this initial economic decline occurs. Through a dissection of the theory of product life-cycle and its suggestion of urban decline from disinvestment of outdated industry, Friedrichs attributes the root cause of shrinking cities as the lack of industrial diversification within specific urban areas. This lack of diversification, Friedrichs suggests, magnifies the political and economic power of the few major companies and weakens the workers' ability to insulate against disinvestment and subsequent deindustrialization of cities. Friedrichs suggests that lack of urban economic diversity prevents a thriving industrial center and disempowers workers. This, in turn, allows a few economic elites in old-industrial cities such as St. Louis, Missouri and Detroit in the United States, to reinvest in cheaper and less-regulated third world manufacturing sites. The result of this economic decline in old-industrial cities is the subsequent out-migration of unemployed populations.
Neoliberal critique
Recent studies have further built upon the product life-cycle theory of shrinking cities. Many of these studies, however, focus specifically on the effects of globalization on urban decline through a critique of neoliberalism. This contextualization is used to highlight globalization and the internationalization of production processes as a major driver causing both shrinking cities and destructive development policies. Many of these articles draw upon case studies looking at the economic relationship between the United States and China to clarify and support the main argument presented. The neoliberal critique of globalization argues that a major driver of shrinking cities in developed countries is through the outflow of capital into developing countries. This outflow, according to theorists, is caused by an inability for cities in richer nations to find a productive niche in the increasingly international economic system. In terms of disinvestment and manufacturer movement, the rise of China's manufacturing industry from United States outsourcing of cheap labor is often cited as the most applicable current example of the product life-cycle theory. Dependency theory has also been applied to this analysis, arguing that cities outside of global centers experience outflow as inter-urban competition occurs. Based on this theory, it is argued that with the exception of a few core cities, all cities eventually shrink as capital flows outward.
Suburbanization
The migration of wealthier individuals and families from industrial city centers into surrounding suburban areas is an observable trend seen primarily within the United States during the mid to late 20th century. Specific theories for this flight vary across disciplines. The two prevalent cultural phenomenons of white flight and car culture are, however, consensus trends across academic disciplines.
White flight
White flight generally refers to the movement of large percentages of Caucasian Americans out of racially mixed United States city centers and into largely homogenous suburban areas during the 20th century. The result of this migration, according to theorists studying shrinking cities, was the loss of money and infrastructure from urban centers. As the wealthier and more politically powerful populations fled from cities, so too did funding and government interest. The result, according to many academics, was the fundamental decline of urban health across United States cities beginning in the 20th century.
The product of white flight was a stratification of wealth with the poorest (and mostly minority) groups in the center of cities and the richest (and mostly white) outside the city in suburban locations. As suburbanization began to increase through to the late 20th century, urban health and infrastructure precipitously dropped. In other words, United States urban areas began to decline.
Mid-20th-century political policies greatly contributed to urban disinvestment and decline. Both the product and intent of these policies were highly racial oriented. Although discrimination and racial segregation already existed prior to the passage of the National Housing Act in 1934, the structural process of discrimination was federally established with the Federal Housing Administration (FHA). The result of the establishment of the FHA was redlining. Redlining refers to the demarcation of certain districts of poor, minority urban populations where government and private investment were discouraged. The decline of minority inner city neighborhoods was worsened under the FHA and its policies. Redlined districts could not improve or maintain a thriving population under conditions of withheld mortgage capital.
Car culture and urban sprawl
In combination with the racial drivers of white flight, the development of a uniquely American car culture also led to further development of suburbanization and later, urban sprawl. As car culture made driving "cool" and a key cultural aspect of "American-ness," suburban locations proliferated in the imaginations of Americans as the ideal landscape to live during the 20th century. Urban decline, under these conditions, only worsened.
The more recent phenomenon of urban sprawl across American cities such as Phoenix and Los Angeles, were only made possible under the conditions of a car culture. The impact of this car culture and resulting urban sprawl is, according to academics, threefold. First, although urban sprawl in both shrinking and growing cities have many similar characteristics, sprawl in relation to declining cities may be more rapid with an increasing desire to move out of the poor, inner-city locations. Second, there are many similarities in the characteristics and features of suburban areas around growing and declining cities. Third, urban sprawl in declining cities can be contained by improving land use within inner city areas such as implementing micro-parks and implementing urban renewal projects. There are many similarities between urban sprawl in relation to both declining and growing cities. This, therefore, provides similar intervention strategies for controlling sprawl from a city planning point of view.
Interventions
Different interventions are adopted by different city governments to deal with the problem of city shrinkage based on their context and development. Governments of shrinking cities such as Detroit and Youngstown have used new approaches of adapting to populations well below their peak, rather than seeking economic incentives to boost populations to previous levels before shrinkage and embracing growth models.
Green retirement city
Research from Europe proposes "retirement migration" as one strategy to deal with city shrinkage. The idea is that abandoned properties or vacant lots can be converted into green spaces for retiring seniors migrating from other places. As older individuals migrate into cities they can bring their knowledge and savings to the city for revitalization. Retiring seniors are often ignored by the communities if they are not actively participating in community activities. The green retirement city approach could also have benefits on social inclusion of seniors, such as urban gardening. The approach could also act as a "catalyst in urban renewal for shrinking cities". Accommodations, in the meanwhile, have to be provided including accessibility to community facilities and health care.
Establishing a green retirement city would be a good approach to avoid tragedies like the 1995 Chicago heat wave. During the heat wave, hundreds of deaths occurred in the city, particularly in the inner neighborhood of the city. Victims were predominantly poor, elderly, African American populations living in the heart of the city. Later research pointed out that these victims were socially isolated and had a lack of contact with friends and families. People who were already very ill in these isolated, inner neighborhoods were also affected and might have died sooner than otherwise. The high crime rate in the inner decaying city also accounted for the high rate of deaths as they were afraid to open their windows. Therefore, a green retirement city with sufficient community facilities and support would accommodate needs for elderly population isolated in the poor, inner city communities.
Right-sizing
The idea of "right-sizing" is defined as "stabilizing dysfunctional markets and distressed neighborhoods by more closely aligning a city's built environment with the needs of existing and foreseeable future populations by adjusting the amount of land available for development." Rather than revitalize the entire city, residents are relocated into concentrated or denser neighborhoods. Such reorganization encourages residents and businesses in more sparsely populated areas to move into more densely populated areas. Public amenities are emphasized for improvement in these denser neighborhoods. Abandoned buildings in these less populated areas are demolished and vacant lots are reserved for future green infrastructure.
The city of Detroit has adopted right-sizing approaches in its "Detroit Work Project" plan. Many neighborhoods are only 10–15% occupied, and the plan encourages people to concentrate in nine of the densest neighborhoods. Under the plan, the city performs several tasks including: prioritizing public safety, providing reliable transportation and demolition plans for vacant structures.
Although the "right-sizing" approach may seem attractive to deal with vast vacant lots and abandoned houses with isolated residents, it can be problematic for people who are incapable of moving into these denser neighborhoods. In the case of Detroit, although residents in decaying neighborhoods are not forced to move into concentrated areas, if they live outside designated neighborhoods they may not get public services they require. This is because communities in shrinking cities often are low-income communities where they are racially segregated. Such segregation and exclusion may "contribute to psychosocial stress level" as well and further add burden to the quality of living environments in these communities.
Smart shrinkage
The idea of "smart shrinkage", in some regards, is similar to dominant growth-based models that offer incentives encouraging investment to spur economic and population growth, and reverse shrinkage. However, rather than believing the city can return to previous population levels, the governments embrace shrinkage and accept having a significantly smaller population. With this model, governments emphasize diversifying their economy and prioritizing funds over relocating people and neighborhoods.
Youngstown 2010 is an example of such an approach for the city of Youngstown, Ohio. The plan seeks to diversify the city's economy, "which used to be almost entirely based on manufacturing". Tax incentive programs like Youngstown Initiative have also "assisted in bringing in and retaining investment throughout the city." Since the plan was introduced, many major investments have been made in the city. The downtown Youngstown has been also transformed from a high crime rate area into a vibrant destination.
Nevertheless, there are concerns that the smart shrinkage approach may worsen existing isolation of residents who cannot relocate to more vibrant neighborhoods. Environmental justice issues may surface from this approach if city governments ignore the types of industries planning investment and neighborhoods that are segregated.
Land bank
Land banks are often quasi-governmental counties or municipal authorities that manage the inventory of surplus vacant lands. They "allow local jurisdictions to sell, demolish and rehabilitate large numbers of abandoned and tax-delinquent properties." Sometimes, the state works directly with local governments to allow abandoned properties to have easier and faster resale and to discourage speculative buying.
One of the most famous examples of land banks is the Genesee County Land Bank in the city of Flint, Michigan. As an industrial city with General Motors as the largest producer, declining car sales with the availability of cheap labor in other cities led to reduction in the labor force of the city. The main reason of the property or land abandonment problem in Flint was the state's tax foreclosure system. Abandoned properties were either transferred to private speculators or became state-owned property through foreclosure, which encouraged low-end reuse of tax-reverted land due to the length of time between abandonment and reuse.
The Land Bank provides a series of programs to revitalize shrinking cities. In the case of Flint, Brownfield Redevelopment for previous polluted lands is controlled by the land bank to allow financing of demolition, redevelopment projects and clean up through tax increment financing. A "Greening" strategy is also promoted by using abandonment as an opportunity for isolated communities to engage in maintenance and improvement of vacant lots. In the city, there is significant reduction in abandoned properties. Vacant lots are maintained by the banks or sold to adjacent land owners as well.
Establishment of land banks could increase land values and tax revenues for further innovation of the shrinking cities. Nevertheless, The process of acquiring foreclosures can be troublesome as "it may require involvement on the part of several jurisdictions to obtain clear title," which is necessary for redevelopment. Economic problems that local residents have, including income disparities between local residents, cannot be solved by the land bank, with the addition of increasing rents and land values led by the revitalization of vacant land. Local leaders also lack the authority to interrupt works that Land Banks do. Environmental justice problems that are from previous polluting industry may not be fully addressed through shrinking city intervention and without opinions from local people. Therefore, a new approach of dealing with these vacant lots will be to work with non-profit local community groups to construct more green open spaces among the declining neighborhoods to reduce vacant lots and create strong community commitments.
Other approaches
Cities have used several other interventions to deal with city shrinkage. One such is the series of policies adopted in the city of Leipzig in East Germany. They include construction of town houses in urban areas and Wächterhäuser, 'guardian houses' with temporary rental-free leases. Temporary use of private property as public spaces is also encouraged. Altena, near Dortmund, has addressed the issue through partnership with civil society and the integration of immigrants. Another intervention is the revitalization of vacant lots or abandoned properties for artistic development and artists interactions such as the Village of Arts and Humanities in North Philadelphia, where vacant lots and empty buildings are renovated with mosaics, gardens and murals.
Environmental justice
A rapidly contracting population is often viewed holistically, as a citywide and sometimes even regional struggle. However, shrinking cities, by their nature and how local officials respond to the phenomena, can have a disproportionate social and environmental impact on the less fortunate, resulting in the emergence of issues relating to environmental injustices. This paradigm was established almost immediately after cities started shrinking in significance during the mid-20th century and persists today in varying forms.
Historical precedent
Although the concept of environmental justice and the movement it sparked was formally introduced and popularized starting in the late 1980s, its historical precedent in the context of shrinking cities is rooted in mid-20th century trends that took place in the United States.
In an American context, historical suburbanization and subsequent ill-fated urban renewal efforts are largely why the very poor and people of color are concentrated in otherwise emptied cities, where they are adversely plagued by conditions which are today identified as environmental injustices or environmental racism. These conditions, although created and exacerbated through mid-20th century actions, still persist today in many cases and include: living in close proximity to freeways; living without convenient access, if any, to healthy foods and green space. Unlike white people, people of color were socially and legally barred from taking advantage of federal government policy encouraging suburban flight. For example, the early construction of freeways coupled with practices such as redlining and racially restrictive covenants, physically prevented people of color from participating in the mass migration to the suburbs, leaving them in – what would become – hollowed and blighted city cores. Because income and race are deeply embedded in understanding the formation of suburbs and shrinking cities, any interventions responding to the shrinking city phenomenon will almost invariably confront issues of social and environmental justice. It is not the case in Europe, where suburbanization has been less extreme, and drivers of shrinking cities are also more closely linked to aging demographics, and deindustrialization.
Case studies
In addition to discriminatory policy-driven decisions of the past, which caused cities to contract in population and created inhospitable living conditions for the poor and people of color in urban cores, environmental justices concerns also arise in present initiatives that seek solutions for cities struggling with considerable population losses.
New Orleans
New Orleans, like many major American cities, saw its population decrease considerably over the latter half of the 20th century, losing almost 50% of the population from its peak in 1960. In large part because of white flight and suburbanization, the population loss perpetuated existing racial segregation and left people of color (mostly African Americans) in the city center. By 2000, vacant and abandoned properties made up 12% of the housing stock. The city was struggling economically and in the wake of Hurricane Katrina, 134,344 of 188,251 occupied housing units sustained reportable damage, and 105,155 of them were severely damaged. Because of historical settlement patterns formed by racial restrictions in the first half of the 20th century, African Americans were disproportionately impacted by the destruction.
Responding to Hurricane Katrina, New Orleans Mayor C. Ray Nagin formed the Bring New Orleans Back Commission in September 2005. The goal of the commission was to assist in redevelopment decision-making for the city. The commission shared its proposal for redevelopment in January 2006, however it faced some criticism related to environmental justice concerns. The commission's proposal was presented prior to many residents having returned to the city and their homes. The process was not very inclusive, particularly with locals of impacted areas, who were predominantly from disadvantaged communities. While the proposal addressed future potential flooding by incorporating new parks in low-laying areas to manage storm water, the locations of the proposed greenspaces required the elimination of some of the low-income neighborhoods. Residents largely viewed the proposal as forced displacement and as benefitting primarily more affluent residents. The proposal was roundly rejected by residents and advocates for residents.
A later intervention to alleviate the mounting abandonment and blight (which existed prior to Katrina but was exacerbated by the disaster) was Ordinance No. 22605, enacted by the New Orleans city council in 2007. The rationale for the ordinance was to allow the city to establish a "Lot Next Door" program, which seeks to "assist in the elimination of abandoned or blighted properties; to spur neighborhood reinvestment, enhance stability in the rental housing market, and maintain and build wealth within neighborhoods." The program intended to give owner occupants the opportunity to purchase abutting properties (city acquired properties formerly state-owned or owned by the New Orleans Redevelopment Authority) as a means of returning properties to neighborhood residents. It later expanded to allow any individual to purchase a property if that person or a family member would live there. The impact of the program, however, was unevenly distributed throughout the city. Although black neighborhoods in the low-laying topographical regions were hit the hardest by Katrina, affluent neighborhoods with high rates of owner occupancy better absorbed vacant and abandoned properties than areas with more rental units.
Detroit
Perhaps the city most commonly associated with the concept of shrinking cities, Detroit too has grappled with issues of environmental justice. Detroit's current circumstances, as it struggles to deal with a population less than half of that from its peak in 1950, are partially the direct result of the same racist process, which left only the poor and people of color in urban city centers. The city presently faces economic strain since only six percent of the taxable value of real estate in the tri-county Detroit area is in the city of Detroit itself while the remaining ninety-four percent is in the suburbs. In recent years, the city has made attempts, out of necessity, to address both its economic and population decline.
In 2010, Detroit mayor David Bing introduced a plan to demolish approximately 10,000 of an estimated 33,000 vacant homes in the city because they were "vacant, open, and dangerous". The decision was driven by the reality that for financial constraints, the city's existing resources simply could not maintain providing services to all areas. However, the decision also reflected a desire to "right-size" Detroit by relocating residents from dilapidated neighborhoods to "healthy" ones. The idea of right-sizing and repurposing Detroit, however, is a contentious issue. Some locals are determined to stay put in their homes while others compare the efforts to past segregation and forced relocation. Mayor Bing clarified that people would not be forced to move, but residents in certain parts of the city "need to understand they're not going to get the kind of services they require."
In addition to right-sizing Detroit as a means to deal with a massively decreased city population and economic shortfall, Mayor Bing also undertook budget cuts.
Although often necessary and painful, certain cuts, such as those to the city's bus services can produce harms in an environmental justice framework. In Detroit, despite the city's massive size and sprawl, roughly 26% of households have no automobile access, compared to 9.2% nationally. From an environmental justice perspective this is significant because a lack of automobile access, coupled with poor transit and historic decentralization, perpetuates what is often referred to as a spatial mismatch. While wealth and jobs are on the outskirts of the metropolitan region, disadvantaged communities are concentrated in the inner-city, physically far from employment without a means of getting there. Indeed, almost 62% of workers are employed outside the city limit, and many depend on public transit. Some contend that for Detroit this situation should more specifically be termed a "modal mismatch" because the poor of the inner-city are disadvantaged because they lack automobile access in a region designed for automobiles.
Regardless of name, the situation is little different and still embedded in historic racial and environmental injustices; the poor are clustered in an inner-city from past policies, which were often racially discriminatory, and cuts to public transportation reduce job accessibility for the many households in Detroit that lack automobile access.
See also
Climate justice
Counterurbanization
Environmental justice
Environmental racism
Human migration
Urban sprawl
References
External links
Shrinking Cities. Research and Exhibition Project
SCiRN™ (The Shrinking Cities International Research Network)
Interview with German expert Wolfgang Kil on Shrinking Cities in Germany
Professor Hollander's research on shrinking cities
Urban studies and planning terminology
Demography
Urban decay
de:Stadtplanung#Aktuelle Themen der Stadtplanung | Shrinking city | Environmental_science | 6,906 |
40,546 | https://en.wikipedia.org/wiki/Jurij%20Vega | Baron Jurij Bartolomej Vega (also Veha; ; ; born Vehovec, March 23, 1754 – September 26, 1802) was a Slovene mathematician, physicist and artillery officer.
Early life
Born to a farmer's family in the small village of Zagorica east of Ljubljana in Slovenia, Vega was 6 years old when his father Jernej Veha died. Vega was educated first in Moravče and later attended high school for six years (1767–1773) in Ljubljana (the Jesuit College of Ljubljana, ), studying Latin, Greek, religion, German, history, geography, science, and mathematics. At that time there were about 500 students there. He was a schoolfellow of Anton Tomaž Linhart, a Slovenian writer and historian. Vega finished high school when he was 19, in 1773. After completing his studies at the Lyceum of Ljubljana (Licej v Ljubljani) he became a navigational engineer in 1775. Tentamen philosophicum, a list of questions for his comprehensive examination, was preserved and is available in the Mathematical Library in Ljubljana. The problems cover logic, algebra, metaphysics, geometry, trigonometry, geodesy, stereometry, geometry of curves, ballistics, and general and special physics.
Military service
Vega left Ljubljana five years after graduation and entered military service in 1780 as a professor of mathematics at the Artillery School in Vienna. At that time he started to sign his last name as Vega and no longer Veha. When Vega was 33 he married Josefa Svoboda (Jožefa Swoboda) (1771–1800), a Czech noble from České Budějovice who was 16 at that time.
Vega participated in several wars. In 1788 he served under Austrian Imperial Field-Marshal Ernst Gideon von Laudon (1717–1790) in a campaign against the Turks at Belgrade. His command of several mortar batteries contributed considerably to the fall of the Belgrade fortress. Between 1793 and 1797 he fought French Revolutionaries under the command of Austrian General Dagobert-Sigismond de Wurmser (1724–1797) with the European coalition on the Austrian side. He fought at Fort Louis, Mannheim, Mainz, Wiesbaden, Kehl, and Dietz. In 1795 he had two 30-pound (14 kilogram) mortars cast, with conically drilled bases and a greater charge, for a firing range up to 3000 metres (3300 yards). The old 60 lb (27 kg) mortars had a range of only 1800 m (2000 yd).
In September 1802 Vega was reported missing. After a few days' search his body was found. The police report concluded that his death was an accident. It is believed that he died on 26 September 1802 in Nußdorf on the Danube, near the Austrian capital, Vienna.
Mathematical accomplishments
Vega published a series of books of logarithm tables. The first one appeared in 1783. Much later, in 1797 it was followed by a second volume that contained a collection of integrals and other useful formulae. His Handbook, which was originally published in 1793, was later translated into several languages and appeared in over 100 issues. His major work was Thesaurus Logarithmorum Completus (Treasury of all Logarithms) that was first published 1794 in Leipzig (its 90th edition was published in 1924). This mathematical table was actually based on Adriaan Vlacq's tables, but corrected a number of errors and extended the logarithms of trigonometric functions for the small angles. An engineer, Franc Allmer, honourable senator of the Graz University of Technology, has found Vega's logarithmic tables with 10 decimal places in the Museum of Carl Friedrich Gauss in Göttingen. Gauss used this work frequently and he has written in it several calculations. Gauss has also found some of Vega's errors in the calculations in the range of numbers, of which there are more than a million. A copy of Vega's Thesaurus belonging to the private collection of the British mathematician and computing pioneer Charles Babbage (1791–1871) is preserved at the Royal Observatory, Edinburgh.
Over the years Vega wrote a four-volume textbook Vorlesungen über die Mathematik (Lectures about Mathematics). Volume I appeared in 1782 when he was 28 years old, Volume II in 1784, Volume III in 1788 and Volume IV in 1800. His textbooks also contain interesting tables: for instance, in Volume II one can find closed form expressions for sines of multiples of 3 degrees, written in a form easy to work with.
Vega wrote at least six scientific papers. On August 20, 1789, Vega achieved a world record when he calculated pi to 140 places, of which the first 126 were correct. This calculation he proposed to the Russian Academy of Sciences in Saint Petersburg in the booklet V. razprava (The fifth discussion), where he had found with his calculating method an error on the 113th place from the estimation of Thomas Fantet de Lagny (1660–1734) from 1719 of 127 places. Vega retained his record 52 years until 1841 and his method is mentioned still today. His article was not published by the academy until six years later, in 1795. Vega had improved John Machin's formula from 1706:
with his formula, which is equal to Euler's formula from 1755:
and which converges faster than Machin's formula. He had checked his result with the similar Hutton's formula:
He had developed the second term in the series only once.
Although he worked in the subjects of ballistics, physics and astronomy, his major contributions are to the mathematics of the second half of the 18th century.
In 1781 Vega tried to push further his idea in the Austrian Habsburg monarchy about the usage of the decimal metric system of units. His idea was not accepted, but it was introduced later under the emperor Franz Josef I in 1871.
Vega was a member of the Academy of Practical Sciences in Mainz, the Physical and Mathematical Society of Erfurt, the Bohemian Scientific Society in Prague, and the Prussian Academy of Sciences in Berlin. He was also an associate member of the British Scientific Society in Göttingen. He was awarded the Order of Maria Theresa on May 11, 1796. In 1800 Vega obtained a title of hereditary baron including the right to his own coat of arms.
Legacy
Jurij Vega High School (Gimnazija Jurija Vege) in Idrija was founded in 1901 as the first Slovene Realschule. In 1935, Vega (crater) on the Moon was named after Vega. The National Bank of Slovenia put into circulation a 50 tolar banknote in his honour in March 1993, and the Slovene Post Office issued a stamp honouring Vega in 1994. In 2004 Slovenia issued coins commemorating his 250th birthday. The asteroid 14966 Jurijvega, discovered on July 30, 1997, is named after him. Slovenia's Vega Astronomical Society is named after both Jurij Vega and the star Vega. The star, however, is not named after Jurij Vega and its name is much older. A free open-source physics library for 3D deformable object simulation, Vega FEM, has also been named after Vega.
Scientific genealogy
Vega is also notable as the tutor and academic advisor of , resulting in a notable scientific genealogy (see Academic genealogy of theoretical physicists: Jurij Vega).
References
External links
Jurij Vega on the Slovenian 50 Tolars banknote.
Georg Freiherr von Vega at MacTutor History of Mathematics archive
Vega and his time
Vega FEM library
1754 births
1802 deaths
18th-century Carniolan people
18th-century mathematicians
18th-century physicists
18th-century astronomers
Carniolan mathematicians
Carniolan physicists
Carniolan astronomers
Ballistics experts
Pi-related people
Austrian barons
Slovene nobility
Carniolan nobility
People from the Municipality of Dol pri Ljubljani
18th-century mathematicians from the Holy Roman Empire
18th-century astronomers from the Holy Roman Empire | Jurij Vega | Mathematics | 1,649 |
75,988,582 | https://en.wikipedia.org/wiki/Cefepime/enmetazobactam | Cefepime/enmetazobactam, sold under the brand name Exblifep, is a medication used for the treatment of urinary tract infections. It is a fixed dose combination containing cefepime, a cephalosporin antibacterial; and enmetazobactam, a beta-lactamase inhibitor.
The combination was approved for medical use in the United States in February 2024, and in the European Union in March 2024.
Medical uses
In the US, cefepime/enmetazobactam is indicated for the treatment of people with complicated urinary tract infections including pyelonephritis, caused by the following susceptible microorganisms: Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus mirabilis, and Enterobacter cloacae complex.
In the EU, cefepime/enmetazobactam is indicated for the treatment of complicated urinary tract infections, including pyelonephritis; hospital-acquired pneumonia, including ventilator-associated pneumonia; and the treatment of people with bacteremia that occurs in association with, or is suspected to be associated with, any of the infections listed above.
History
Enmetazobactam was invented by Orchid Pharma in India and then out-licensed to Allecra Therapeutics for further development.
Society and culture
Legal status
The combination was approved for medical use in the United States in February 2024.
In January 2024, the Committee for Medicinal Products for Human Use of the European Medicines Agency adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Exblifep, intended for the treatment of urinary tract infections and pneumonia in adults. The applicant for this medicinal product is Advanz Pharma Limited. The combination was approved for medical use in the European Union in March 2024.
Names
The combination cefepime/enmetazobactam is sold under the brand name Exblifep.
References
Further reading
External links
Combination drugs | Cefepime/enmetazobactam | Biology | 440 |
14,218,810 | https://en.wikipedia.org/wiki/TorrentFreak |
TorrentFreak (TF) is a blog dedicated to reporting the latest news and trends on the BitTorrent protocol and file sharing, as well as on copyright infringement and digital rights.
The website was started in November 2005 by a Dutchman using the pseudonym "Ernesto van der Sar". He was joined by Andy "Enigmax" Maxwell and Ben Jones in 2007. Regular contributors include Rickard Falkvinge, founder of the Pirate Party. The online publication eCommerceTimes, in 2009, described "Ernesto" as the pseudonym of Lennart Renkema, owner of TorrentFreak. TorrentFreak's text is free content under a Creative Commons Attribution-NonCommercial version 3.0 license.
Their lead researcher and community manager was the Pirate Party activist Andrew Norton, from 2007 until 2022.
Specialist areas
According to Canadian law scholar Michael Geist, TorrentFreak "is widely used as a source of original reporting on digital issues".
Frequent areas of reporting include:
The City of London's Police Intellectual Property Crime Unit
United States Trade Representative and Notorious Markets reports
Anti-piracy web blocking
Torrent tracker news
VPN and seedbox reviews
File sharing website news
Copyright law news
Warez scene news
As well as other news affecting copyright, privacy, file sharing and adjacent topics.
Editorial stance
In a 2021 article, Andy Maxwell outlined TorrentFreak's editorial stance. He wrote: "As a publication entirely dedicated to reporting on copyright, piracy, torrent and streaming sites (plus all things closely related), here at TorrentFreak we aim to tell all 'sides' of the story. We do not shy away from reports that show that piracy hurts sales and we have no problem publishing research projects that show completely the opposite. It's called balanced reporting and it hurts absolutely no one."
History
On 17 August 2007, TorrentFreak reported that Comcast had begun throttling its upload bandwidth, specifically against BitTorrent users. This made seeding, which is an essential part of the BitTorrent protocol, effectively impossible. It was later determined that Comcast was using Sandvine products, which implement network traffic shaping and policing, and include support for both blocking new and forcefully terminating established network connections. Comcast has denied these claims whenever they have been asked to comment. A guide, for customer service representatives when asked about Comcast's BitTorrent throttling, was leaked to The Consumerist on 26 October 2007.
In October 2008 through to March 2011 TorrentFreak ran a short lived video news service titled 'torrentfreak.tv', directed by Andrej Preston, founder of torrent site Suprnova made available for streaming and download on Mininova.
On 21 August 2013, Comcast threatened TorrentFreak for writing about publicly available court documents. The underlying document links a Comcast subscriber with the Prenda Law firm. The court case where the document was filed was a copyright infringement lawsuit brought by AF Holdings for alleged infringement of an adult movie.
In August 2013, Sky Broadband blocked the site for UK customers after torrent site EZTV pointed its DNS servers to TorrentFreak's IP address and, in July 2014, the site was blocked by the controversial Sky Broadband Shield parental filter system.
References
External links
News websites
File sharing communities
BitTorrent
Publications established in 2005
Free-content websites
Copyright infringement
File sharing news sites | TorrentFreak | Technology | 704 |
22,270,008 | https://en.wikipedia.org/wiki/Slit%20%28protein%29 | Slit is a family of secreted extracellular matrix proteins which play an important signalling role in the neural development of most bilaterians (animals with bilateral symmetry). While lower animal species, including insects and nematode worms, possess a single Slit gene, humans, mice and other vertebrates possess three Slit homologs: Slit1, Slit2 and Slit3. Human Slits have been shown to be involved in certain pathological conditions, such as cancer and inflammation.
The ventral midline of the central nervous system is a key place where axons can either decide to cross and laterally project or stay on the same side of the brain. The main function of Slit proteins is to act as midline repellents, preventing the crossing of longitudinal axons through the midline of the central nervous system of most bilaterian animal species, including mice, chickens, humans, insects, nematode worms and planarians. It also prevents the recrossing of commissural axons. Its canonical receptor is Robo but it may have other receptors. The Slit protein is produced and secreted by cells within the floor plate (in vertebrates) or by midline glia (in insects) and diffuses outward. Slit/Robo signaling is important in pioneer axon guidance.
Discovery
Slit mutations were first discovered in the Nuesslein-Volhard/Wieschaus patterning screen where they were seen to affect the external midline structures in the embryos of Drosophila melanogaster, also known as the common fruit fly. In this experiment, researchers screened for different mutations in D. melanogaster embryos that affected the neural development of axons in the central nervous system. They found that the mutations in commissureless genes (Slit genes) lead to the growth cones that typically cross the midline remaining on their own side. The findings from this screening suggest that Slit genes are responsible for repulsive signaling along the neuronal midline.
Structure
Slit1, Slit2, and Slit3 each have the same basic structure. A major identifying feature of the Slit protein is the four leucine-rich repeat (LRR) domains and the N-terminus. Slits are one of only two protein families that contain multiple LRR domains. These LRRs are followed by six repeats similar to epidermal growth factors (EGF) as well as a β-sandwich domain similar to laminin G. Directly after these sequences, invertebrates have one EGF repeat, whereas vertebrates have three EGF repeats. In each case, the EGF is followed by a C-terminal cystine knot (CT) domain.
It is possible for Slits to be cleaved into fragments of the N-terminus and C-terminus as a result of an assumed proteolytic site between the fifth and sixth EGFs in Drosophila Slit, Caenorhabditis elegans Slit, rat Slit1, rat Slit3 and human Slit2.
LRR domains
Slit LRR domains are thought to assist in controlling neurite outgrowth. The domains consist of five to seven LRRs each with disulfide-rich cap segments. Each LRR motif contains a LXXLXLXXN sequence (where L = leucine, N = asparagine, X = any amino acid) which is one strand to a parallel β-sheet on the concave face of the LRR domain, while the back side of the domain consists of irregular loops. Each of the four domains of Slit are connected by short "linkers" which attach to the domains via a disulfide bridge, allowing the LRR region of Slit to remain very compact.
Vertebrate homologs
Slit1, Slit2, and Slit3 are all a human homologs of the 'Slit' gene found in Drosophila. Each of these genes secretes a protein containing protein-protein interaction regions with leucine-rich repeats and EFGs. Slit2 is mainly expressed in the spinal cord, where it repels motor axons. Slit1 functions in the brain, and Slit3 in the thyroid. Both Slit1 and Slit2 are found in the murine postnatal septum as well as in the neocortex. Further, Slit2 participates in inhibiting leukocyte chemotaxis. In rats, Slit1 was found in the neurons of adult and fetal forebrains. This shows that Slit proteins in mammals most likely contribute to the process of forming and maintaining the endocrine and nervous systems through interactions between proteins. Slit3 is primarily expressed in the thyroid, in human umbilical vein endothelial cells (HUVECs), as well as in endothelial cells from the lung and diaphragm of the mouse. Slit3 interacts with Robo1 and Robo4.
Function
Guidance molecules
Guidance molecules act as cues by carrying information to receptive cells; administering this information which tells the cell and its entities how to properly align. Slit proteins behave as such when working in axonal guidance during the development of the nervous system. Similarly, these proteins help to orchestrate the development of various networks of tissues throughout the body. This role, also described as cell migration, is the primary role of Slit when interacting with Robo. It is most commonly found acting in neurons, endothelial cells and cancer cells.
Axon guidance
Chemorepellents help to direct growing axons toward the correct regions by directing them away from inappropriate regions. Slit genes, as well as their roundabout receptors, act as chemorepellents by helping prevent the wrong types of axons from crossing the midline of the central nervous system during establishment or remodeling of the neural circuits. The binding of Slit to any member of the Roundabout receptor family results in axon repelling through changes in the axon growth cone. The resulting repelling of axons is collectively termed as axonal guidance. Slit1 and Slit2 have both been seen to collapse and repel olfactory axons. Further evidence suggests that Slit also directs interneurons, particularly acting in the cortex. Positive effects are also correlated with slits. Slit2 begins the formation of axon branches through neural growth factor genes of the dorsal root ganglia.
Organogenesis
Several studies have shown that the interaction of Slit with its receptors is crucial in regulating the processes involved with the formation of organs. As previously discussed, these interactions play a key role in cell migration. Not surprisingly then, this gene has been found expressed during the development of tightly regulated tissues, such as the heart, lungs, gonads, and ovaries. For example, in early development of the heart tube in Drosophila, Slit and two of its Robo receptors guide migrating cardioblasts and pericardial cells in the dorsal midline. In addition, research on mice has shown that Slit3 and its interaction with Robo1 may be crucial to the development and maturation of lung tissue. Similarly, the expression of Slit3 is upregulated when aligning airway epithelium with endothelium. Due to its regulating function in tissue development, absence or mutations in the expression of these genes can result in abnormalities of these tissues. Several studies in mice and other vertebrates have shown that this deficit results in death almost immediately after birth.
Angiogenesis
The Slit2 protein has recently been discovered to be associated with the development of new blood vessels from pre-existing vessels, or angiogenesis. Recent research has debated on whether this gene inhibits or stimulates this process. There has been significant proof to conclude that both are true, depending on the context. It has been concluded that the role of Slit in this process depends on which receptor it binds, the cellular context of its target cells, and/or other environmental factors. Slit2 has been implicated in promoting angiogenesis in mice (both in vitro and in vivo), in the human placenta, and in tumorigenesis.
Clinical importance
Because of their part in forebrain development, during which they contribute to axonal guidance and guiding signals in the movement of cortical interneurons, Slit-Robo signal transduction mechanisms could possibly be used in therapy and treatment of neurological disorders and certain types of cancer. Procedures have been found in which Slit genes allow for precise control over vascular guidance cues influencing the organization of blood vessels during development. Slit also plays a large role in angiogenesis. With increased knowledge of this relationship, treatments could be developed for complications with development of embryo vasculature, female reproductive cycling, tumor grown, and metastasis, ischemic cardiovascular diseases, or ocular disorders.
Cancer
Due to its pivotal role in controlling cell migration, abnormalities or absences in the expression of Slit1, Slit2 and Slit3 are associated with a variety of cancers. In particular, Slit-Robo interaction has been implicated in reproductive and hormone dependent cancers, particularly in females. Under normal function, these genes act as tumor suppressors. Therefore, deletion or lack of expression of these genes is associated with tumorigenesis, particularly tumors within the epithelium of the ovaries, endometrium, and cervix. Samples of surface epithelium in cancer ridden ovaries has exhibited that these cells show decreased expression of Slit2 and Slit3. In addition, absence of these genes allows the migration of cancer cells and thus is associated with increased cancer progression and increased metastasis. The role of this gene and its place in cancer treatment and development is becoming increasingly unraveled but increasingly complex.
References
Developmental neuroscience
Protein families | Slit (protein) | Biology | 1,981 |
11,516,599 | https://en.wikipedia.org/wiki/Activation%20product | An activation product is a material that has been made radioactive by the process of neutron activation.
Fission products and actinides produced by neutron absorption of nuclear fuel itself are normally referred to by those specific names, and activation product reserved for products of neutron capture by other materials, such as structural components of the nuclear reactor or nuclear bomb, the reactor coolant, control rods or other neutron poisons, or materials in the environment. All of these, however, need to be handled as radioactive waste. Some nuclides originate in more than one way, as activation products or fission products.
Activation products in a reactor's primary coolant loop are a main reason reactors use a chain of two or even three coolant loops linked by heat exchangers.
Fusion reactors will not produce radioactive waste from the fusion product nuclei themselves, which are normally just helium-4, but generate high neutron fluxes, so activation products are a particular concern.
Activation product radionuclides include:
[1] Branching fractions from LNHB database.
[2] Branching fractions renormalised to sum to 1.0..
References
External links
Handbook on Nuclear Activation Cross-Sections, IAEA, 1974
Nuclear Structure and Decay Databases (nndc.bnl.gov)
New and revised half-life measurements results made by the Radioactivity Group of NIST
HANDBOOK OF NUCLEAR DATA FOR SAFEGUARDS: DATABASE EXTENSIONS, AUGUST 2008
Radiation
Neutron
Radiation effects
Nuclear materials | Activation product | Physics,Chemistry,Materials_science,Engineering | 294 |
568,726 | https://en.wikipedia.org/wiki/Giant%20star | A giant star has a substantially larger radius and luminosity than a main-sequence (or dwarf) star of the same surface temperature. They lie above the main sequence (luminosity class V in the Yerkes spectral classification) on the Hertzsprung–Russell diagram and correspond to luminosity classes II and III. The terms giant and dwarf were coined for stars of quite different luminosity despite similar temperature or spectral type (namely K and M) by Ejnar Hertzsprung in 1905 or 1906.
Giant stars have radii up to a few hundred times the Sun and luminosities between 10 and a few thousand times that of the Sun. Stars still more luminous than giants are referred to as supergiants and hypergiants.
A hot, luminous main-sequence star may also be referred to as a giant, but any main-sequence star is properly called a dwarf, regardless of how large and luminous it is.
Formation
A star becomes a giant after all the hydrogen available for fusion at its core has been depleted and, as a result, leaves the main sequence. The behaviour of a post-main-sequence star depends largely on its mass.
Intermediate-mass stars
For a star with a mass above about 0.25 solar masses (), once the core is depleted of hydrogen it contracts and heats up so that hydrogen starts to fuse in a shell around the core. The portion of the star outside the shell expands and cools, but with only a small increase in luminosity, and the star becomes a subgiant. The inert helium core continues to grow and increase in temperature as it accretes helium from the shell, but in stars up to about it does not become hot enough to start helium burning (higher-mass stars are supergiants and evolve differently). Instead, after just a few million years the core reaches the Schönberg–Chandrasekhar limit, rapidly collapses, and may become degenerate. This causes the outer layers to expand even further and generates a strong convective zone that brings heavy elements to the surface in a process called the first dredge-up. This strong convection also increases the transport of energy to the surface, the luminosity increases dramatically, and the star moves onto the red-giant branch where it will stably burn hydrogen in a shell for a substantial fraction of its entire life (roughly 10% for a Sun-like star). The core continues to gain mass, contract, and increase in temperature, whereas there is some mass loss in the outer layers., § 5.9.
If the star's mass, when on the main sequence, was below approximately , it will never reach the central temperatures necessary to fuse helium., p. 169. It will therefore remain a hydrogen-fusing red giant until it runs out of hydrogen, at which point it will become a helium white dwarf., § 4.1, 6.1. According to stellar evolution theory, no star of such low mass can have evolved to that stage within the age of the Universe.
In stars above about the core temperature eventually reaches 108 K and helium will begin to fuse to carbon and oxygen in the core by the triple-alpha process.,§ 5.9, chapter 6. When the core is degenerate helium fusion begins explosively, but most of the energy goes into lifting the degeneracy and the core becomes convective. The energy generated by helium fusion reduces the pressure in the surrounding hydrogen-burning shell, which reduces its energy-generation rate. The overall luminosity of the star decreases, its outer envelope contracts again, and the star moves from the red-giant branch to the horizontal branch., chapter 6.
When the core helium is exhausted, a star with up to about has a carbon–oxygen core that becomes degenerate and starts helium burning in a shell. As with the earlier collapse of the helium core, this starts convection in the outer layers, triggers a second dredge-up, and causes a dramatic increase in size and luminosity. This is the asymptotic giant branch (AGB) analogous to the red-giant branch but more luminous, with a hydrogen-burning shell contributing most of the energy. Stars only remain on the AGB for around a million years, becoming increasingly unstable until they exhaust their fuel, go through a planetary nebula phase, and then become a carbon–oxygen white dwarf., § 7.1–7.4.
High-mass stars
Main-sequence stars with masses above about are already very luminous and they move horizontally across the HR diagram when they leave the main sequence, briefly becoming blue giants before they expand further into blue supergiants. They start core-helium burning before the core becomes degenerate and develop smoothly into red supergiants without a strong increase in luminosity. At this stage they have comparable luminosities to bright AGB stars although they have much higher masses, but will further increase in luminosity as they burn heavier elements and eventually become a supernova.
Stars in the range have somewhat intermediate properties and have been called super-AGB stars. They largely follow the tracks of lighter stars through RGB, HB, and AGB phases, but are massive enough to initiate core carbon burning and even some neon burning. They form oxygen–magnesium–neon cores, which may collapse in an electron-capture supernova, or they may leave behind an oxygen–neon white dwarf.
O class main sequence stars are already highly luminous. The giant phase for such stars is a brief phase of slightly increased size and luminosity before developing a supergiant spectral luminosity class. Type O giants may be more than a hundred thousand times as luminous as the sun, brighter than many supergiants. Classification is complex and difficult with small differences between luminosity classes and a continuous range of intermediate forms. The most massive stars develop giant or supergiant spectral features while still burning hydrogen in their cores, due to mixing of heavy elements to the surface and high luminosity which produces a powerful stellar wind and causes the star's atmosphere to expand.
Low-mass stars
A star whose initial mass is less than approximately will not become a giant star at all. For most of their lifetimes, such stars have their interior thoroughly mixed by convection and so they can continue fusing hydrogen for a time in excess of years, much longer than the current age of the Universe. They steadily become hotter and more luminous throughout this time. Eventually they do develop a radiative core, subsequently exhausting hydrogen in the core and burning hydrogen in a shell surrounding the core. (Stars with a mass in excess of may expand at this point, but will never become very large.) Shortly thereafter, the star's supply of hydrogen will be completely exhausted and it is expected to become a helium white dwarf, although the universe is too young for any such star to exist yet, so no star with that history has ever been observed.
Subclasses
There are a wide range of giant-class stars and several subdivisions are commonly used to identify smaller groups of stars.
Subgiants
Subgiants are an entirely separate spectroscopic luminosity class (IV) from giants, but share many features with them. Although some subgiants are simply over-luminous main-sequence stars due to chemical variation or age, others are a distinct evolutionary track towards true giants.
Examples:
Gamma Geminorum (γ Gem), an A-type subgiant;
Eta Bootis (η Boo), a G-type subgiant.
Delta Scorpii (δ Sco), a B-type subgiant.
Bright giants
Bright giants are stars of luminosity class II in the Yerkes spectral classification. These are stars which straddle the boundary between ordinary giants and supergiants, based on the appearance of their spectra. The bright giant luminosity class was first defined in 1943.
Well known stars which are classified as bright giants include:
Canopus
Albireo
Epsilon Canis Majoris
Theta Scorpii
Beta Draconis
Alpha Herculis
Gamma Canis Majoris
Red giants
Within any giant luminosity class, the cooler stars of spectral class K, M, S, and C, (and sometimes some G-type stars) are called red giants. Red giants include stars in a number of distinct evolutionary phases of their lives: a main red-giant branch (RGB); a red horizontal branch or red clump; the asymptotic giant branch (AGB), although AGB stars are often large enough and luminous enough to get classified as supergiants; and sometimes other large cool stars such as immediate post-AGB stars. The RGB stars are by far the most common type of giant star due to their moderate mass, relatively long stable lives, and luminosity. They are the most obvious grouping of stars after the main sequence on most HR diagrams, although white dwarfs are more numerous but far less luminous.
Examples:
Pollux, a K-type giant.
Epsilon Ophiuchi, a G-type red giant.
Arcturus (α Boötis), a K-type giant.
R Doradus, a M-type giant.
Mira (ο Ceti), an M-type giant and prototype Mira variable.
Aldebaran, a K-type giant
Yellow giants
Giant stars with intermediate temperatures (spectral class G, F, and at least some A) are called yellow giants. They are far less numerous than red giants, partly because they only form from stars with somewhat higher masses, and partly because they spend less time in that phase of their lives. However, they include a number of important classes of variable stars. High-luminosity yellow stars are generally unstable, leading to the instability strip on the HR diagram where the majority of stars are pulsating variables. The instability strip reaches from the main sequence up to hypergiant luminosities, but at the luminosities of giants there are several classes of pulsating variable stars:
RR Lyrae variables, pulsating horizontal-branch class A (sometimes F) stars with periods less than a day and amplitudes of a magnitude of less;
W Virginis variables, more-luminous pulsating variables also known as type II Cepheids, with periods of 10–20 days;
Type I Cepheid variables, more luminous still and mostly supergiants, with even longer periods;
Delta Scuti variables, includes subgiant and main-sequence stars.
Yellow giants may be moderate-mass stars evolving for the first time towards the red-giant branch, or they may be more evolved stars on the horizontal branch. Evolution towards the red-giant branch for the first time is very rapid, whereas stars can spend much longer on the horizontal branch. Horizontal-branch stars, with more heavy elements and lower mass, are more unstable.
Examples:
Sigma Octantis (σ Octantis), an F-type giant and a Delta Scuti variable;
Capella Aa (α Aurigae Aa), a G-type giant.
Beta Corvi (β Corvi), a G-type bright giant.
Blue (and sometimes white) giants
The hottest giants, of spectral classes O, B, and sometimes early A, are called blue giants. Sometimes A- and late-B-type stars may be referred to as white giants.
The blue giants are a very heterogeneous grouping, ranging from high-mass, high-luminosity stars just leaving the main sequence to low-mass, horizontal-branch stars. Higher-mass stars leave the main sequence to become blue giants, then bright blue giants, and then blue supergiants, before expanding into red supergiants, although at the very highest masses the giant stage is so brief and narrow that it can hardly be distinguished from a blue supergiant.
Lower-mass, core-helium-burning stars evolve from red giants along the horizontal branch and then back again to the asymptotic giant branch, and depending on mass and metallicity they can become blue giants. It is thought that some post-AGB stars experiencing a late thermal pulse can become peculiar blue giants.
Examples:
Meissa (λ Orionis A), an O-type giant.
Alcyone (η Tauri), a B-type giant, the brightest star in the Pleiades;
Thuban (α Draconis), an A-type giant.
See also
List of nearest giant stars
References
External links
Interactive giant-star comparison.
Star types | Giant star | Astronomy | 2,583 |
41,635,197 | https://en.wikipedia.org/wiki/Zinc%20Inc. | Zinc Inc. (renamed from Cotap Inc, Jun 2016) is a San Francisco-based company that sells a mobile messaging application for businesses. Unlike consumer-focused apps such as WhatsApp and WeChat that require phone numbers, Cotap allows users to find and connect with other users who share their corporate email domain. The company was founded in May 2013 by former Yammer executives Jim Patterson and Zack Parker. That month, Cotap announced it had received $5.5 million in a Series A funding round from Charles River Ventures and Emergence Capital Partners. Cotap received $10M in Series B funding in January 2014.
Cotap released its first app, which is available for iOS, in October 2013. In February 2014 Cotap released a native Android app. In August 2014, Cotap released a Mac and Web app alongside the announcement of cloud storage integrations with Box, Dropbox, Google Drive and OneDrive. Both iOS and Android apps, as well as the Mac and Web apps, allow users to send individual and group messages.
On raising $5M in a funding round led by Emergence Capital Partners and Charles River Ventures, Cotap changed its name to Zinc and appointed a new Chief Executive, Stacey Epstein.
In April 2017 a further $11M round of investment was raised from GE Ventures, Hearst Ventures and existing investors Emergence & Charles River.
Zinc was acquired by ServiceMax in 2019 for an undisclosed amount.
References
Mobile software
2013 establishments in California
Defunct software companies of the United States | Zinc Inc. | Technology | 303 |
11,389,841 | https://en.wikipedia.org/wiki/Single-subject%20research | Single-subject research is a group of research methods that are used extensively in the experimental analysis of behavior and applied behavior analysis with both human and non-human participants. This research strategy focuses on one participant and tracks their progress in the research topic over a period of time. Single-subject research allows researchers to track changes in an individual over a large stretch of time instead of observing different people at different stages. This type of research can provide critical data in several fields, specifically psychology. It is most commonly used in experimental and applied analysis of behaviors. This research has been heavily debated over the years. Some believe that this research method is not effective at all while others praise the data that can be collected from it. Principal methods in this type of research are: A-B-A-B designs, Multi-element designs, Multiple Baseline designs, Repeated acquisition designs, Brief experimental designs and Combined designs.
These methods form the heart of the data collection and analytic code of behavior analysis. Behavior analysis is data driven, inductive, and disinclined to hypothetico-deductive methods.
Experimental questions
Experimental questions are decisive in determining the nature of the experimental design to be selected. There are four basic types of experimental questions: demonstration, comparison, parametric, and component. A demonstration is "Does A cause or influence B?". A comparison is "Does A1 or A2 cause or influence B more?". A parametric question is "How much of A will cause how much change or influence on B?". A component question is "Which part of A{1,2,3} - A1 or A2 or A3... - causes or influences B?" where A is composed of parts that can be separated and tested.
The A-B-A-B design is useful for demonstration questions.
A-B-A-B
A-B-A-B
A-B-A-B designs begin with establishing a baseline (A #1) then introduce a new behavior or treatment (B #1). Then there is a return to the baseline (A #2) by removing B #1. B #2 is a return of the new behavior or treatment.
A-B
An AB design is a two-part or phase design composed of a baseline ("A" phase) with no changes and a treatment or intervention ("B") phase. If there is a change then the treatment may be said to have had an effect. However, it is subject to many possible competing hypotheses, making strong conclusions difficult. Variants on the AB design introduce ways to control for the competing hypotheses to allow for stronger conclusions.
Reversal or A-B-A
The reversal design is the most powerful of the single-subject research designs showing a strong reversal from baseline ("A") to treatment ("B") and back again. If the variable returns to baseline measure without a treatment then resumes its effects when reapplied, the researcher can have greater confidence in the efficacy of that treatment. However, many interventions cannot be reversed, some for ethical reasons (e.g., involving self-injurious behavior, smoking) and some for practical reasons (they cannot be unlearned, like a skill).
Further ethics notes: It may be unethical to end an experiment on a baseline measure if the treatment is self-sustaining and highly beneficial and/or related to health. Control condition participants may also deserve the benefits of research once all data has been collected. It is a researcher's ethical duty to maximize benefits and to ensure that all participants have access to those benefits when possible.
A-B-C
The A-B-C design is a variant that allows for the extension of research questions around component, parametric and comparative questions.
Multielement
Multi-element designs sometimes referred to as alternating-treatment designs are used in order to ascertain the comparative effect of two treatments. Two treatments are alternated in rapid succession and correlated changes are plotted on a graph to facilitate comparison. Multi-element designs are typically used in Single-subject research to accurately test multiple independent variables at once.
Multiple baseline
The multiple baseline design was first reported in 1960 as used in basic operant research. It was applied in the late 1960s to human experiments in response to practical and ethical issues that arose in withdrawing apparently successful treatments from human subjects. In it two or more (often three) behaviors, people or settings are plotted in a staggered graph where a change is made to one, but not the other two, and then to the second, but not the third behavior, person or setting. Differential changes that occur to each behavior, person or in each setting help to strengthen what is essentially an AB design with its problematic competing hypotheses.
Multiple baseline tests are used to determine the helpfulness of an intervention. By focusing daily data collection on one participant, researchers can prepare to expand their research. This research method yields a high amount of data that can be analyzed by researchers. This data can then be used to support a researchers hypothesis and/or give insight before moving on to a group research project.
Repeated Acquisition
In addition to multiple baseline designs, a way to deal with problematic reversibility is the use of repeated acquisitions.
Brief
A designed favored by applied settings researchers where logistical challenges, time and other limits make research difficult are variants of multi-element and A-B-A-B type designs.
Combined
Combined Single-subject research is used to gain added knowledge on the research question and are used to make group research run better. The combined design has arisen from a need to obtain answers to more complex research questions. Combining two or more single-case designs, such as A-B-A-B and multiple baseline, may produce such answers.
Multipleprobe
Popular in Verbal Behavior research, the multipleprobe research design has elements of the other research designs.
Changing-Criterion
In a changing-criterion research design a criterion for reinforcement is changed across the experiment to demonstrate a functional relation between the reinforcement and the behavior.
See also
Single-subject design
N of 1 trial
Applied behavior analysis
Verbal behavior
B.F. Skinner
References
Sources
HAINS, ANN HIGGINS. “Multi-Element Designs for Early Intervention Research.” Journal of Early Intervention, vol. 15, no. 2, 1991, pp. 185–192., https://doi.org/10.1177/105381519101500207.
Design of experiments
Behaviorism | Single-subject research | Biology | 1,326 |
1,562,796 | https://en.wikipedia.org/wiki/Aresti%20Catalog | The Aresti Catalog is the Fédération Aéronautique Internationale (FAI) standards document enumerating the aerobatic manoeuvers permitted in aerobatic competition. Designed by Spanish aviator Colonel José Luis Aresti Aguirre (1919–2003), each figure in the catalog is represented by lines, arrows, geometric shapes and numbers representing the precise form of a manoeuver to be flown.
The catalog broadly classifies manoeuvers into numbered families. Families 1 through 8 depict basic figures, such as turns, loops and vertical lines; family 9 depicts rotational elements that can be added to basic figures to increase difficulty, change the direction of flight or invert the g-loading of the aircraft.
Notation
In Aresti notation, solid lines represent upright or positive-g manoeuvers and dashed lines represent inverted or negative-g manoeuvers; these are sometimes depicted in red. Thick dot represents the beginning of the manoeuver, while a short perpendicular line represents the end. Stalled wing manoeuvers such as spins and snap (flick) rolls are represented by triangles. Arrows represent rolling manoeuvers with numbers representing the extent and number of segments of the roll.
The catalog assigns each manoeuver a unique identifier, called a catalog number, and difficulty factor, represented by the symbol K. When a basic figure is combined with one or more rolling elements, the resultant figure K is the sum of all component Ks. During an aerobatics competition, judges grade the execution of each manoeuver with a value between 10 (perfect) and 0 (highly flawed). Each figure's grades are multiplied by its K and summed to yield a total raw score for the flight.
Notational systems for aerobatic manoeuvers have been used since the 1920s.
The first system accepted worldwide was published by French aviator François d'Huc Dressler in 1955 and 1956. It was used for international competitions through 1962.
José Aresti's development of a notation for aerobatic figures began while serving as an instructor in the Jerez Pilot Training School in the 1940s. By the end of 1961 Aresti published a dictionary of some 3,000 aerobatic manoeuvers, the Sistema Aerocryptographica Aresti. Then employed throughout Spain, the Spanish Aero Club urged its adoption internationally. The FAI's Aerobatics Commission, CIVA, elected to use the catalog beginning at the World Aerobatic Championships held in Bilbao, Spain in 1964; it has been in use worldwide and has evolved continually since then. Though the catalog had grown at one time to some 15,000 manoeuvers, a CIVA working group substantially streamlined it in the mid-1980s.
Following Aresti's death, a court fight ensued between his heirs and FAI, which once provided a free catalog online. The catalog is now only available in printed form for a fee from Aresti System S.L.
Software is available to design and display aerobatic sequences using Aresti notation.
Notes
External links
An article explaining Aresti notation.
Aerobatic competitions
Notation | Aresti Catalog | Mathematics | 640 |
27,431,403 | https://en.wikipedia.org/wiki/Shadowing%20lemma | In the theory of dynamical systems, the shadowing lemma is a lemma describing the behaviour of pseudo-orbits near a hyperbolic invariant set. Informally, the theory states that every pseudo-orbit (which one can think of as a numerically computed trajectory with rounding errors on every step) stays uniformly close to some true trajectory (with slightly altered initial position)—in other words, a pseudo-trajectory is "shadowed" by a true one. This suggests that numerical solutions can be trusted to represent the orbits of the dynamical system. However, caution should be exercised as some shadowing trajectories may not always be physically realizable.
Formal statement
Given a map f : X → X of a metric space (X, d) to itself, define a ε-pseudo-orbit (or ε-orbit) as a sequence of points such that belongs to a ε-neighborhood of .
Then, near a hyperbolic invariant set, the following statement holds:
Let Λ be a hyperbolic invariant set of a diffeomorphism f. There exists a neighborhood U of Λ with the following property: for any δ > 0 there exists ε > 0, such that any (finite or infinite) ε-pseudo-orbit that stays in U also stays in a δ-neighborhood of some true orbit.
See also
Chaotic systems
Butterfly effect
References
External links
Shadowing Theorem on Scholarpedia
Can a butterfly in Brazil control the climate of Texas?
Dynamical systems
Lemmas | Shadowing lemma | Physics,Mathematics | 301 |
7,820,422 | https://en.wikipedia.org/wiki/Nivarox | Nivarox, also known as Nivarox - FAR SA is a Swiss company formed by a merger in 1984 between Nivarox SA and Fabriques d'Assortiments Réunis (FAR). It is currently owned by the Swatch Group. Nivarox is also the trade name of the metallic alloy from which its products are fabricated. Its notable property is that its coefficient of elasticity is remarkably constant with temperature. Nivarox is most famous for producing hairsprings that are attached to the balance wheel inside a mechanical watch movement, as well as mainsprings which provide the motive power for the watch.
Nivarox was developed for use in watch hairsprings in 1933 by Reinhard Straumann in his Waldenbourg laboratory. FAR was the corporate name chosen in 1932 for the entity comprising several companies and subsidiaries located in Le Locle Switzerland, which at the time manufactured various watch components.
Nivarox alloy
As a trade name, Nivarox is an acronym from the German . The Nivarox alloy is a nickel iron alloy used mainly in the watch industry for hairsprings for balance wheels, but also in other micro-machine industries and in certain medical equipment and surgical instruments, in the same category as Elinvar, Ni-Span, Vibralloy, Nivaflex and other similar alloys. The "non-variable" refers to the alloy's most notable property: that it has a low temperature coefficient of elasticity; its elasticity does not change much with temperature. There are several versions of the Nivarox alloy depending upon the intended application: Nivarox-CT, but also with suffixes CTC, M, W. Chemical compositions vary in wt% as follows for all Nivarox alloys : Iron as balance, a wide variation in nickel between 30-40%, beryllium 0.7-1%, some versions have molybdenum at 6-9% while others have instead chromium 8%, titanium is present in some compositions at 1%, manganese at 0.7-0.8%, silicon 0.1-0.2% and carbon in traces up to 0.2%. A typical composition would be for the early version Nivarox-CT (by wt %) : Fe 54%, Ni 38%, Cr 8%, Ti 1%, Si 0.2%, Mn 0.8%, Be 0.9%, C < 0.1%.
When used for critical watch components, the alloy reduces errors due to temperature variation. Hairsprings made of this alloy have a spring constant which does not vary with temperature, allowing the watch's balance wheel, its timekeeping element, to keep better time. Along with the earlier alloy Elinvar, this alloy made obsolete the expensive compensation balance used in precision timepieces in the 19th century. Nivarox springs are now used by most watchmakers worldwide, with a global market share of 90%. The alloys also see limited use for specific components of sensitive scientific instruments.
External links
References
Nickel alloys
Horology
Manufacturing companies of Switzerland | Nivarox | Physics,Chemistry | 645 |
34,380,017 | https://en.wikipedia.org/wiki/Barium%20perchlorate | Barium perchlorate is a powerful oxidizing agent, with the formula Ba(ClO4)2. It is used in the pyrotechnic industry.
Barium perchlorate decomposes at 505 °C.
Structure of barium perchlorate trihydrate
Gallucci and Gerkin (1988) analyzed the structure of the hydrate isomer barium perchlorate trihydrate (Ba(ClO4)2•3H2O) by X-ray crystallography. The barium ions are coordinated by six water oxygen atoms at 2.919Å and six perchlorate oxygens at 3.026Å in a distorted icosahedral arrangement. The perchlorate fails by a narrow margin to have regular tetrahedral geometry, and has an average Cl-O bond length of 1.433Å. The space-group assignment of the structure was resolved, with the centrosymmetric assignment of P63/m confirmed. Each axial perchlorate oxygen is hydrogen bonded to three water molecules and each trigonal oxygen is hydrogen bonded to two water molecules. This interaction is the reason that the perchlorate fails to be tetrahedral. Gallucci and Gerkin surmised that the water molecule H atoms lie in the plane at z = and .
Preparation
Barium perchlorate can be prepared using many different reagents and methods. One method involves evaporating a solution containing barium chloride and an excess of perchloric acid. The dihydrate form is produced by recrystallizing and drying to a constant weight. Additional drying over sulfuric acid yields the monohydrate. The anhydrous form is obtained by heating to 140 °C in vacuum. Dehydration of barium perchlorate that does not occur in vacuum will also result in hydrolysis of the perchlorate. Other reactions that produce barium perchlorate are as follows: perchloric acid and barium hydroxide or carbonate; potassium perchlorate and hydrofluosilicic acid followed with barium carbonate; boiling solution of potassium chlorate and zinc fluosilicate. For large-scale manufacturing purposes, barium perchlorate is synthesized by evaporating a solution of sodium perchlorate and barium chloride. Another method of preparation involves the digestion of a saturated solution of ammonium perchlorate with hydrated barium hydroxide in 5-10% excess of the theoretical amount.
Applications
Due to its characteristic as a powerful oxidation agent, one of barium perchlorate’s primary uses is in the manufacture and preparation of explosive emulsions and other explosive compounds. Using an emulsifier makes the process of transporting and handling of the explosive material while still retaining its destructive properties at the end point of use. Perchlorate explosives were mainly used in industrial applications, such as mining during the 1920s.
Barium perchlorate is also able to complex with the quinolone antibacterial agents ciprofloxacin and norfloxacin. FTIR data suggests that CIP and NOR act as bidentate ligands, using the ring carbonyl oxygen and an oxygen of the carboxylic group. This coordination is significant because it increases the solubility of the antibiotics in water and other polar solvents, increasing their uptake efficiency.
Because of its high solubility in water, anhydrous barium perchlorate can be used as a dehydrating reagent for other compounds. Due to its high solubility, ease of preparation, low cost, stability at high temperatures, and relatively ease of regeneration, barium perchlorate is a favored compound for dehydrating compounds. The need for dehydrating compounds has increased with the use of chemical reactions employing gases under pressure, as the water must be removed from the air prior to the reaction taking place.
Barium perchlorate is also used for the determination of small concentrations (down to 10 ppm, with an accuracy of +/- 1 ppm) of sulfate. In order for the titration to be successful, a high concentration of a nonaqueous solvent, such as ethyl alcohol, 2-propanol, or methanol, must be present. Thorin is typically used as the indicator.
References
Perchlorates
Barium compounds
Oxidizing agents | Barium perchlorate | Chemistry | 904 |
28,404,157 | https://en.wikipedia.org/wiki/Ministry%20of%20Mines%20and%20Energy%20%28Colombia%29 | The Ministry of Mines and Energy () is the national executive ministry of the Government of Colombia that oversees the regulation of the mining and mineral industry and the electricity sector in Colombia, it is similar in its duties to other energy ministries of other countries.
List of ministers
References
Ministries established in 1974
Colombia
Colombia
Mining in Colombia
Energy in Colombia | Ministry of Mines and Energy (Colombia) | Engineering | 67 |
42,957,113 | https://en.wikipedia.org/wiki/Grigore%20T.%20Popa | Grigore T. Popa (sometimes Anglicized to Gregor T. Popa; 1 May 1892 – 18 July 1948) was a Romanian physician and public intellectual. Of lowly peasant origin, he managed to obtain a university education and become a professor at two of his country's leading universities. An anatomist by specialty, Popa worked on popularizing modern science, reforming the medical and higher education systems, and, in war hospitals, as a decorated and publicly acclaimed practitioner. His work in endocrinology and neuromorphology was valued abroad, while at home he helped train a generation of leading doctors.
Ill-treated by successive fascist dictatorships, Popa adhered to moderate left-wing ideals and publicized them by means of his review, Însemnări Ieșene. He criticized Marxism as much as scientific racism, but condemned Romania's participation in the war against the Soviets, and, in 1944, joined a protest movement of high-profile academics. During his final years, his anticommunism and his Christian democratic stances brought him into conflict with the authorities. The Communist Romanian regime drove him out of his teaching position and harassed him until his death in middle age. Upon the restoration of democracy, his alma mater and the school where he taught for much of his career was named in his honor.
Biography
Origins and early career
Born in Șurănești, Vaslui County, his parents Maria and Toader were poor răzeși, peasants who owned their own plot of land. The family was related to Emil Condurachi, future historian and archeologist. Grigore, the couple's eleventh child, was intellectually precocious. His mother noticed his aptitude early on, and despite great material difficulties, including selling off their land so he could finish high school, his parents managed to provide him with an education. As argued by historian Lucian Boia, Popa's lowly origin and his successful career stand as evidence of an "upward social mobility" in the pre-1944 Kingdom of Romania.
Raised a Romanian Orthodox, Popa blended his belief in core Christian principles with an interest in science. At the age of fifteen, he translated Ernst Haeckel's General Morphology into Romanian and obtained the author's written permission to publish. He would later translate Gray's Anatomy as well. Popa graduated from the National College in Iași and entered the Natural Sciences faculty of the local university. However, as his parents had no more money for his schooling and there were no scholarships left, he switched to the Medical faculty, where there was one scholarship, even though the field did not attract him.
Upon seeing cadavers being dissected for the first time, he fainted and had to be revived with cold water by an assistant. However, he persevered in his studies and was helped in particular by two professors, Nicolae Hortolomei and Francisc Rainer, becoming the latter's assistant after graduation. As later noted by surgeon Ilie Th. Riga, who was his colleague on Rainer's team, "we lived for years in the most select atmosphere that education may breed": "It is to [Rainer] that we owe our character, the awakening of our scientific interest". During World War I, Popa cared for the wounded and sick at Iași's Sfântul Spiridon Hospital, earning him a knighthood in the Order of the Crown. In May 1918, following Romania's withdrawal from war, Popa applied to rejoin Rainer's team in Bucharest, where Rainer was performing experimental surgery on wounded soldiers. Late in 1918, Popa also joined A. C. Cuza's regionalist group for Moldavian intellectuals—the Brotherhood of Unified Moldavia. Leading the Brotherhood's student center, he spoke in public about the United Principalities' 60th anniversary, expressing his sadness that this had not been celebrated as a national holiday in Iași.
In July 1918, he married Florica Cernătescu, a university classmate. A native of Huși, her maternal grandfather was the chemist Petru Poni. Also trained by Rainer and herself a decorated wartime physician, she went on to become associate professor of Histology and his closest scientific collaborator over the years. The couple had two sons and two daughters. Popa eventually followed Rainer to the University of Bucharest's medical faculty in 1920, and was appointed assistant professor. With Rainer as his doctoral advisor, Popa completed his docent degree, describing the functional structure of the dura mater. Over the course of his career, his students included some twenty-two university professors and Romanian Academy members, among them George Emil Palade and Constantin Bălăceanu-Stolnici.
Rise to prominence
By January 1924, when Rainer's alleged Jewish extraction made him a target of antisemitic agitation among the students, Popa became Rainer's voice in professional disputes. As such, he accused a Iași anatomist, Victor Papilian, of plagiarism, and published his take on the matter in the Bucharest daily Adevărul. Papilian retorted with accusations of sectarianism against Popa, Rainer, and the whole "Bucharest school": "a sterile and envious school", "a grand society of mutual admirers, wherein master and students have declared each other geniuses". Popa identified Iași with extreme nationalism, and, in a 1925 article for the student review Viața Universitară, accused the far-right National-Christian Defense League of hypocrisy. As he noted, its "hatred and brutality" were not just aimed at Jews, but also at Romanians coming in from Bessarabia, since the latter were ostensibly socialists.
With Rainer's help, Popa received a Rockefeller Foundation fellowship in 1925. He had a direct experience of America, and of what he liked to call its "guided democracy", which was rare among Romanians of his generation, and which he recorded in detail in diaries he intended for publishing. He spent the first year in Chicago, the second at the Marine Biological Laboratory in Woods Hole and finishing by studying Anatomy and Embryology in 1927–1928 at University College Hospital Medical School, under Grafton Elliot Smith. His scientific activity, after his work on the dura mater, focused on three areas: the hypothalamic–pituitary–adrenal axis, the reform of medical education at the university level, and the physiology of spontaneous movement (motility) in spermatozoa. Regarding the first area, he worked in London alongside the Australian Una Fielding; together they discovered the vascular link between the hypothalamus and the pituitary gland, publishing their findings on the hypophyseal portal system in medical journals between 1930 and 1935, presenting them before the Royal Medical Society in 1935. Working alongside his Romanian colleague, Eugen Lucinescu, Popa also returned to anatomy with a study on the "mechanostructure" of the pericardium.
In 1928, Popa became professor of anatomy at Iași, the city associated with his rivals. For many years he taught histology, Anatomical Pathology and Legal Medicine, as required, and was also curator of Sfântul Spiridon Hospital, as well as head of the Physicians and Naturalists' Society. His confrontation with the city's antisemitic far-right became direct. In late 1929, he presided over a commission tasked with investigating the race riot at Iași medical faculty. He found that the Jewish and Romanian students were racially segregated during teaching hours, which contributed to the tensions, but could not identify students directly responsible for the incident.
With time, Popa became a noted public speaker in support of modernization, and a popularizer of Western science. In 1931, he gave a public lecture on "The Former and Current Situation of Iași", which recognized that the city had greatly decayed, materially and culturally, since 1866. He attributed this decline to psychological factors (a city with "depressed", "disinterested" and "filthy" inhabitants), but also to clientelism and the excessive powers of the central government. On Washington's Birthday, 1932, he discussed "The Scientific Spirit in America and in Europe" at the Friends of America society in Bucharest. An admirer of the British educational model, he was a research fellow at the University of Cambridge for four to six months a year in 1927–1930, 1932 and 1935–1938. He was also Romania's sole representative to the University of London Centennial, in 1936.
A corresponding member of the Romanian Academy from 1936, Grigore T. Popa was Dean of the Iași medical faculty for two years, from 1938 to 1940. At around that time, he drifted apart from his mentor Rainer, and relations between them became "tense". According to a popular account that Popa repeatedly challenged, Rainer had claimed the discovery of the hypophyseal portal system some years before Popa and Fielding.
Antifascism
In January 1936, together with writers Mihail Sadoveanu, George Topîrceanu and Mihai Codreanu, Popa founded Însemnări Ieșene ("Recordings from Iași"), a magazine of commentary. With his intercession, the original group grew to include other intellectuals, including philosopher Ion Petrovici and physician-novelist I. I. Mironescu. He also used the magazine to popularize the anthropological work of his former teacher, Elliott Smith. Însemnări Ieșene ran for four years, coinciding with the peak of political turmoil. It borrowed inspiration from Viața Românească, Romania's classical tribune of social criticism, with Popa joining in the trend. As argued in 2012 by author Constantin Coroiu, Popa expanded the magazine's focus beyond cultural matters: "He takes up issues, analyses and criticizes mindsets, mores, inertia, cowardice, grave failures of character, and, what's more, the scourges of Romanian, and even European, society in his own day and ever since."
At Însemnări Ieșene, which, under Topîrceanu's guidance, made efforts to preserve its political independence, Popa took a firm stand against the violently fascist Iron Guard, and denounced scientific racism. As noted by Boia, Popa took "moderately left-wing positions and [was] persistent in his defense of democracy." According to his student Bălăceanu-Stolnici, he had "a left-wing orientation of the British Labourite kind". Citing the need for intellectual freedom, he publicly defended Sadoveanu, who was being attacked by his far-right colleagues, with pieces in the left-leaning newspaper Dimineața. Although active in such civil society causes, he was never a member of a political party, and also administered criticism to the establishment National Peasants' Party. In his articles for Însemnări Ieșene, he accuses the National Peasantists of corruption and politicking.
Popa criticized the breakdown of Romanian democracy and the creation of a National Renaissance Front (FRN) dictatorship in 1938, describing it as "unprecedented lunacy or the actual perversion of leadership". He decried the new authoritarian Constitution as an act of capitulation to "political militancy and cultural inferiority", even as his colleagues in the literary world had come to endorse it. That year, in an obituary piece for the socialist physician Ioan Cantacuzino, Popa outlined his own humanist vision of science as a "sacred fire". In his view, material civilization had evolved faster than culture, unwittingly instigating a sort of "pseudo-culture" that opposed progress. He combined Herbert Spencer's take on sociocultural evolution with a measure of genetic determinism, and, against psychological nativism, suggested that all concept of morality was produced by and through evolution; he also held that primitive society, and "semi-civilized" fascism, were regulated by the brainstem, whereas civilization was a realm of the cerebral cortex. When, in 1940, Popa contributed to the FRN regime's magazine, Muncă și Voe Bună, it was to highlight its contribution to working class welfare.
In October 1939—shortly after the Invasion of Poland and the start of World War II—, Însemnări Ieșene published his article deploring man's return to his "beastly" nature and expressing fears that modern life had made soldiers indifferent about transcendentals. Popa witnessed subsequent developments from the side. The National Renaissance Front fell from power after agreeing to territorial losses in favor of Hungary and the Soviet Union. He was part of the Grand Caucus of the university, which issued a reserved protest against the cession of Northern Transylvania. With a special issue and articles in Însemnări Ieșene, Popa also mourned the loss of Bessarabia and Northern Bukovina. Harassed by the Iron Guard, which blacklisted him for assassination, Popa managed to survive its "National Legionary State" regime, proclaimed in September 1940. However, Însemnări Ieșene was banned, with some of its staff members moved to the fascist-inspired Cetatea Moldovei review. A Iași medical faculty purging commission, headed by Iron Guard men, proposed Popa's transfer "to another scientific institution", citing Popa's "left-wing ideas" as a rationale.
The Iron Guard was ultimately toppled in the civil war of January 1941, producing the more lenient fascist dictatorship of Ion Antonescu. In June of that year, Popa was co-opted by the authorities to participate in reeducating Guardist sympathizers. With Gala Galaction, Cicerone Theodorescu and Iuliu Scriban, he lectured students at the Iași Costachi Seminary about the excesses of Guardist dogma. He continued to speak his mind, in particular objecting to Romania's participation in World War II alongside Nazi Germany. He was, as Boia notes, "an intransigent antifascist, [who] would naturally fit into any sort of plot against the regime". In 1942, following Rainer's retirement, he was transferred to Bucharest, where he worked as a professor for four years. After Rainer's death in 1944, he also took over the Anthropological Institute and reattached it to the medical school. While there, Popa wrote a study showing the lack of any scientific basis for Aryanism and asserting that there was no reason to oppress Jews. Traian Săvulescu, afraid to offend Antonescu, refused to publish it; Popa nevertheless read the work before the academy in late 1943. The listeners, few of whom were pro-German, reacted positively. However, a January 1944 address was seen as a veiled attack on the dictator, to whom the members were largely sympathetic, and as a result drew a chillier reaction. One of his conferences at the academy, Reforma Spiritului. Știința ca bază de primenire a omului ("Spiritual Reform. Science as a Basis for Bettering Mankind") objected to Romania's economic dependency, claiming that Romanians were at risk of falling back among "agricultural peoples", those "destined to perpetual ignorance". By that time, the security service, Siguranța Statului, was keeping Popa under constant surveillance.
In April 1944, together with other prominent intellectuals, Popa signed a petition asking Antonescu to seek peace with the Allies and end the war immediately. As noted by Boia, this "academics' memorandum" was belated, and did not expose its signers to any special persecution, since the Red Army was already poised to invade Romania. Its paternity was for long disputed between the semi-active National Peasants' Party, who relied on Popa's friendliness, and the repressed Romanian Communist Party. According to the National Peasantist version of the events, the text had been drafted as early as 1943 by Popa and Ioan Hudiță, and only presented to the communists for signing. Nevertheless, both versions agree that Popa had a fundamental role in the secret negotiations between centrists and communists.
Anticommunism
Popa gave a cautious welcome to the August 1944 Coup which toppled Antonescu, describing it as Romania's "return to normality." Reputedly, he was appointed Minister of Education in one of the cabinet variants shuffled after the coup, but deposed within 15 minutes of his appointment by Soviet representatives. From 1944 to 1946, he was Dean of the Bucharest medical faculty, having been handpicked for the position by Ștefan Voitec, the Social Democrat Education Minister. With the onset of the Soviet occupation and the installation of a Communist Party-led government, he continued to stand up for his principles. In front of communist-run purging committees, he defended on professional grounds those colleagues accused of having sided with fascism, and called for the reinstatement of academic freedom. In January 1945, Democrația, a liberal democratic daily, published Ion Biberi's interview with Popa, where the latter voices the opinion that a truly democratic regime "cannot be tolerant of any form of extremism".
His uncompromising stance stunned members of the Petru Groza cabinet, in particular Voitec. At a conference in 1945, he praised the British and American university systems, drawing a vehement letter of rebuke from Constantin Ion Parhon, who considered the Soviet model as optimal. As noted in 2009 by historian Bogdan Cristian Iacob, Popa's stance showed "a glaring lack of sense for the times", "an incapacity to grasp that the Academy and University were not, at least initially, attacked on the basis of the scholarship produced, but from political positions." According to Iacob, Popa was callous in not showing a willingness to indict those of his medical school colleagues who had careers in the Iron Guard.
Following his clash with Parhon, Popa took the even more drastic step of resigning from the Romanian Society for Friendship with the Soviet Union. Also in 1945, he began aiding Constant Tonegaru's "Mihai Eminescu Society", a secret opposition group that distributed appeals for help to the West. He used his dean's cabinet as a storage room for such anticommunist propaganda. During this period, he was attacked and robbed by a group of three Soviet soldiers, which he interpreted as a warning.
Popa signed his name to a public protest decrying vote-rigging during the November 1946 election; there were ten other signatories, including aviator Smaranda Brăescu and Army General Aurel Aldea. It reached the Allied Commission, and, after being examined by Soviet representatives, served as incriminating evidence for the protesters' repression. Popa's final public appearance took the form of a speech before the academy in April 1947. From an unassuming title, which implied a lecture about "nervous tension and the century's disease", it turned abruptly to political critique, likening the abuses of Nazism to those of communism. Popa's concept of "nervous tension", theorized by Popa from texts by Guglielmo Ferrero, was in fact the collective fear imposed by totalitarianism, which leads man to "hide the reservations imposed by his consciousness." Terror was inevitable, but ultimately inefficient: dictators [...] shall always be powerlessly arrested on the edge of our meditative nervous network, which they cannot control and cannot deform. There, in his own cortex, man still endures free [...]. But if, in order to make sure that they have expunged it, dictators should crucify [their victims], then the spirit, with its invisible vibrations, shall make its way from the crucified to the still-chained, and the miracle of a new resurrection will become possible, the resurrection of freedom, without which humanity would become extinct.
Popa returned to his ideas on "semi-civilization", describing revolution as an enemy of natural selection, in either its Darwinian or Lamarckism (Popa favored neither of the latter theories, viewing them as compatible). With "racism", "historical materialism" was "a dangerous simplification" of human endeavor. He warned that communism, like Nazism, was going to "exterminate, propagating hatred and violence toward any belief but its own." His was also an appeal against immoral but "exact" science, describing ideologues as "disciples of the Antichrist": "In this grave situation, the time has come for any conscience that is still pure to ask themselves: 'Where to?' And the answer will not be hard to find: 'Back to Christian morality!'". According to political scientist Ioan Stanomir, this sample of "Christian democracy" managed to reconcile the political expression of Romanian Orthodoxy, previously monopolized by the far-right, with "political freedom, understood as a set of guarantees against ideological and administrative arbitrariness."
Communist persecution and death
According to Popa's own recollection, the audience sat stone-faced through the delivery of Popa's speech, and rushed for the exits once it was over. More optimistically, Constantin Rădulescu-Motru, a fellow anticommunist academician, wrote that those making an "ostentatious" exit were friends of the Soviet regime, such as Sadoveanu and Parhon. The core public cheered, as if "the Academy were infused with revolt and [...] no one takes for granted the existence of Russian democracy—that blend of dictatorship and gangsterism." As argued by Stanomir, Popa "spoke out inadmissible truths and gave value appraisals to a regime that was just getting ready to impose Stalinist orthodoxy upon the intellectuals. [...] The coming world had discovered a witness that would not hesitate to diagnose it." Within days, Popa was asked to attend a meeting with the Communist Interior Minister, Teohari Georgescu, but he casually refused. When the Gendarmes were dispatched to arrest him at his residence on the university campus, hundreds of students formed a chain and blocked their entrance.
His oppositional stance led to his removal from the academy with the enthusiastic approval of fellow scientists Săvulescu and Parhon, from the deanship and, in 1946, from teaching. This was accomplished with a novel procedure, which formally eliminated ("compressed") the teaching position, but also singled out the person in charge for further inquiry. One individual who fought to force Popa out of teaching was Simion Oeriu, a communist without scientific training who was nonetheless appointed professor against Popa's objections. Another means used to target him was a proposal to admit hundreds of students who had been victims of Nazi oppression in Northern Transylvania, some of whom spoke no Romanian, and award them doctorates in two or three years. When Popa refused, he was called a "reactionary" and even an Iron Guard sympathizer. A first attempt to fire him met with resistance from the medical students, who were very fond of their teacher. When he was ultimately dismissed, he remained unemployed; his lifelong friend Sadoveanu did not intervene.
Although seriously ill with essential hypertension and renal sclerosis, he was unable to enter a hospital. Abandoned by his colleagues and under pressure from the authorities, he withdrew into semi-clandestinity. He and his elder son fled in peasant clothes to Șurănești, then to the home of friends in Baia Mare. By constantly changing addresses and not venturing out into the street, Popa managed to evade arrest and was finally brought home, moribund, at the beginning of July 1948. The authorities were aware of his presence but no longer bothered to detain him. His death soon afterwards came several months after a Communist regime was fully established; the Bucharest university leadership refused to have his coffin publicly displayed. The new dean, Nicolae Gh. Lupu, ordered his family to leave campus.
Over the course of the communist period, there was a concerted effort to banish Popa's memory, even though his 1944 petition to Antonescu was still being officially cited as evidence of a communist-backed resistance movement to fascism. In 1991, following the Romanian Revolution, the Iași medical institute, which had meanwhile been separated from the main university, was renamed the Grigore T. Popa University of Medicine and Pharmacy. The primary school in his native village was also renamed in his honor in 2011. Popa's writings on science, culture and ideology were published by his descendants as Reforma Spiritului ("Spiritual Reform") in 2002. Other essays were collected by physician Richard Constantinescu in a 2008 volume of works by and about Ion Petrovici. This is one of several monographs and anthologies edited by Constantinescu, detailing such topics as Popa's Christian faith and his correspondence with poet-physician Vintilă Ciocâlteu, and including his American diary (published 2014).
Popa's widow was obligated to live in a tiny apartment on the outskirts of Bucharest; she died in 1986, in her mid-90s. One of the couple's sons, Grigore Gr., himself became a doctor, while the other, Tudorel, was an actor. As youngsters, Tudorel Popa and his sister Marilena were both involved with their father in aiding the anticommunist underground. Tudorel Popa's son, Vlad Tudor Popa, is a chemist, head of the Romanian Academy's Institute of Physical Chemistry. Grigore Gr. died in 2006; his son is the novelist and critic Dumitru Radu Popa.
Notes
References
Constantin Bălăceanu-Stolnici, "Ștefan Milcu, un model", in Andrei Kozma, Cristiana Glavce, Constantin Bălăceanu-Stolnici (eds.), Antropologie și interdisciplinaritate. Editura Niculescu, Bucharest, 2014,
Lucian Boia, Capcanele istoriei. Elita intelectuală românească între 1930 și 1950. Humanitas, Bucharest, 2012,
Richard Constantinescu, "Grigore T. Popa și Victor Papilian între 'juriu de onoare' și polemică", Revista Medicală Română, Nr. 1/2011, pp. 37–40
Mihai Drăgănescu, "Grigore T. Popa: O gândire despre cunoaștere, moralitate și societate", Noema, Nr. 1/2002, pp. 2–9
Bogdan Cristian Iacob, "Avatars of the Romanian Academy and the Historical Front: 1948 versus 1955", in Vladimir Tismăneanu (ed.), Stalinism Revisited: The Establishment of Communist Regimes in East-Central Europe. CEU Press, Budapest, 2009,
Lucian Nastasă, "Suveranii" universităților românești. Mecanisme de selecție și promovare a elitei intelectuale, Vol. I. Editura Limes, Cluj-Napoca, 2007,
Arcadiu Petrescu, "Profesor Dr. Grigore T. Popa", in Vasile Igna (ed.), Subteranele memoriei. Editura Universal Dalsi, Bucharest, 2001,
I. Petrovanu, "Grigore T. Popa", in Eugen Târcoveanu, Constantin Romanescu, Mihai Lițu (eds.), 125 de ani de învățământ medical superior la Iași. Ed. Gr. T. Popa, Iași, 2004,
Grigore T. Popa, "Note. Asupra descoperirii sistemului portal hipofizar", Revista Fundațiilor Regale, Nr. 1/1945, pp. 229–231
Dan Riga, Sorin Riga, Ilie Th. Riga, Gheorghe Călin, Anatomie și antropologie. Eseuri și sinteze. Cartea Universitară, Bucharest, 2008,
Ioan Stanomir, "Facerea lumii", in Paul Cernat, Ion Manolescu, Angelo Mitchievici, Ioan Stanomir, Explorări în comunismul românesc. Polirom, Iași, 2004,
1892 births
1948 deaths
Romanian anatomists
Romanian endocrinologists
20th-century Romanian educators
Romanian educational theorists
Alexandru Ioan Cuza University alumni
Academic staff of Alexandru Ioan Cuza University
Academic staff of the University of Bucharest
Deans (academic)
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Critics of Marxism
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20th-century Romanian essayists
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20th-century Romanian diarists | Grigore T. Popa | Biology | 6,141 |
2,258,865 | https://en.wikipedia.org/wiki/Isotopologue | In chemistry, isotopologues (also spelled isotopologs) are molecules that differ only in their isotopic composition. They have the same chemical formula and bonding arrangement of atoms, but at least one atom has a different number of neutrons than the parent.
An example is water, whose hydrogen-related isotopologues are: "light water" (HOH or ), "semi-heavy water" with the deuterium isotope in equal proportion to protium (HDO or ), "heavy water" with two deuterium atoms ( or ); and "super-heavy water" or tritiated water ( or , as well as and , where some or all of the hydrogen is the radioactive tritium isotope). Oxygen-related isotopologues of water include the commonly available form of heavy-oxygen water () and the more difficult to separate version with the isotope. Both elements may be replaced by isotopes, for example in the doubly labeled water isotopologue . Altogether, there are 9 different stable water isotopologues, and 9 radioactive isotopologues involving tritium, for a total of 18. However only certain ratios are possible in mixture, due to prevalent hydrogen swapping.
The atom(s) of the different isotope may be anywhere in a molecule, so the difference is in the net chemical formula. If a compound has several atoms of the same element, any one of them could be the altered one, and it would still be the same isotopologue. When considering the different locations of the same isotope, the term isotopomer, first proposed by Seeman and Paine in 1992, is used.
Isotopomerism is analogous to constitutional isomerism or stereoisomerism of different elements in a structure. Depending on the formula and the symmetry of the structure, there might be several isotopomers of one isotopologue. For example, ethanol has the molecular formula . Mono-deuterated ethanol, or , is an isotopologue of it. The structural formulas and are two isotopomers of that isotopologue.
Singly substituted isotopologues
Analytical chemistry applications
Singly substituted isotopologues may be used for nuclear magnetic resonance experiments, where deuterated solvents such as deuterated chloroform (CDCl or CHCl) do not interfere with the solutes' H signals, and in investigations of the kinetic isotope effect.
Geochemical applications
In the field of stable isotope geochemistry, isotopologues of simple molecules containing rare heavy isotopes of carbon, oxygen, hydrogen, nitrogen, and sulfur are used to trace equilibrium and kinetic processes in natural environments and in Earth's past.
Doubly substituted isotopologues
Measurement of the abundance of clumped isotopes (doubly substituted isotopologues) of gases has been used in the field of stable isotope geochemistry to trace equilibrium and kinetic processes in the environment inaccessible by analysis of singly substituted isotopologues alone.
Currently measured doubly substituted isotopologues include:
Carbon dioxide: COO
Methane: 13CH3D and 12CH2D2
Oxygen: 18O2 and 17O18O
Nitrogen: 15N2
Nitrous oxide: NNO and NNO
Analytical requirements
Because of the relative rarity of the heavy isotopes of C, H, and O, isotope-ratio mass spectrometry (IRMS) of doubly substituted species requires larger volumes of sample gas and longer analysis times than traditional stable isotope measurements, thereby requiring extremely stable instrumentation. Also, the doubly-substituted isotopologues are often subject to isobaric interferences, as in the methane system where CH and CHD ions interfere with measurement of the CHD and CHD species at mass 18. A measurement of such species requires either very high mass resolving power to separate one isobar from another, or modeling of the contributions of the interfering species to the abundance of the species of interest. These analytical challenges are significant: The first publication precisely measuring doubly substituted isotopologues did not appear until 2004, though singly substituted isotopologues had been measured for decades previously.
As an alternative to more conventional gas source IRMS instruments, tunable diode laser absorption spectroscopy has also emerged as a method to measure doubly substituted species free from isobaric interferences, and has been applied to the methane isotopologue CHD.
Equilibrium fractionation
When a light isotope is replaced with a heavy isotope (e.g., C for C), the bond between the two atoms will vibrate more slowly, thereby lowering the zero-point energy of the bond and acting to stabilize the molecule. An isotopologue with a doubly substituted bond is therefore slightly more thermodynamically stable, which will tend to produce a higher abundance of the doubly substituted (or “clumped”) species than predicted by the statistical abundance of each heavy isotope (known as a stochastic distribution of isotopes). This effect increases in magnitude with decreasing temperature, so the abundance of the clumped species is related to the temperature at which the gas was formed or equilibrated. By measuring the abundance of the clumped species in standard gases formed in equilibrium at known temperatures, the thermometer can be calibrated and applied to samples with unknown abundances.
Kinetic fractionation
The abundances of multiply substituted isotopologues can also be affected by kinetic processes. As for singly substituted isotopologues, departures from thermodynamic equilibrium in a doubly-substituted species can implicate the presence of a particular reaction taking place. Photochemistry occurring in the atmosphere has been shown to alter the abundance of O from equilibrium, as has photosynthesis. Measurements of CHD and CHD can identify microbial processing of methane and have been used to demonstrate the significance of quantum tunneling in the formation of methane, as well as mixing and equilibration of multiple methane reservoirs. Variations in the relative abundances of the two NO isotopologues NNO and {{sup>15}}NNO can distinguish whether NO has been produced by bacterial denitrification or by bacterial nitrification.
Multiple substituted isotopologues
Biochemical applications
Multiple substituted isotopologues may be used for nuclear magnetic resonance or mass spectrometry experiments, where isotopologues are used to elucidate metabolic pathways in a qualitative (detect new pathways) or quantitative (detect quantitative share of a pathway) approach. A popular example in biochemistry is the use of uniform labelled glucose (U-13C glucose), which is metabolized by the organism under investigation (e. g. bacterium, plant, or animal) and whose signatures can later be detected in newly formed amino acid or metabolically cycled products.
Mass spectrometry applications
Resulting from either naturally occurring isotopes or artificial isotopic labeling, isotopologues can be used in various mass spectrometry applications.
Applications of natural isotopologues
The relative mass spectral intensity of natural isotopologues, calculable from the fractional abundances of the constituent elements, is exploited by mass spectrometry practitioners in quantitative analysis and unknown compound identification:
To identify the more likely molecular formulas for an unknown compound based on the matching between the observed isotope abundance pattern in an experiment and the expected isotope abundance patterns for given molecular formulas.
To expand the linear dynamic response range of the mass spectrometer by following multiple isotopologues, with an isotopologue of lower abundance still generating linear response even while the isotopologues of higher abundance giving saturated signals.
Applications of isotope labeling
A compound tagged by replacing specific atoms with the corresponding isotopes can facilitate the following mass spectrometry methods:
Metabolic flux analysis (MFA)
Stable isotopically labeled internal standards for quantitative analysis
See also
Mass (mass spectrometry)
Isotope-ratio mass spectrometry
Isotopomer
Clumped isotopes
Isotopocule
References
External links
Fractional abundance of atmospheric isotopologues, SpectralCalc.com
Isotopes | Isotopologue | Physics,Chemistry | 1,688 |
61,406,091 | https://en.wikipedia.org/wiki/Decomposition%20of%20a%20module | In abstract algebra, a decomposition of a module is a way to write a module as a direct sum of modules. A type of a decomposition is often used to define or characterize modules: for example, a semisimple module is a module that has a decomposition into simple modules. Given a ring, the types of decomposition of modules over the ring can also be used to define or characterize the ring: a ring is semisimple if and only if every module over it is a semisimple module.
An indecomposable module is a module that is not a direct sum of two nonzero submodules. Azumaya's theorem states that if a module has an decomposition into modules with local endomorphism rings, then all decompositions into indecomposable modules are equivalent to each other; a special case of this, especially in group theory, is known as the Krull–Schmidt theorem.
A special case of a decomposition of a module is a decomposition of a ring: for example, a ring is semisimple if and only if it is a direct sum (in fact a product) of matrix rings over division rings (this observation is known as the Artin–Wedderburn theorem).
Idempotents and decompositions
To give a direct sum decomposition of a module into submodules is the same as to give orthogonal idempotents in the endomorphism ring of the module that sum up to the identity map. Indeed, if , then, for each , the linear endomorphism given by the natural projection followed by the natural inclusion is an idempotent. They are clearly orthogonal to each other ( for ) and they sum up to the identity map:
as endomorphisms (here the summation is well-defined since it is a finite sum at each element of the module). Conversely, each set of orthogonal idempotents such that only finitely many are nonzero for each and determine a direct sum decomposition by taking to be the images of .
This fact already puts some constraints on a possible decomposition of a ring: given a ring , suppose there is a decomposition
of as a left module over itself, where are left submodules; i.e., left ideals. Each endomorphism can be identified with a right multiplication by an element of R; thus, where are idempotents of . The summation of idempotent endomorphisms corresponds to the decomposition of the unity of R: , which is necessarily a finite sum; in particular, must be a finite set.
For example, take , the ring of n-by-n matrices over a division ring D. Then is the direct sum of n copies of , the columns; each column is a simple left R-submodule or, in other words, a minimal left ideal.
Let R be a ring. Suppose there is a (necessarily finite) decomposition of it as a left module over itself
into two-sided ideals of R. As above, for some orthogonal idempotents such that . Since is an ideal, and so for . Then, for each i,
That is, the are in the center; i.e., they are central idempotents. Clearly, the argument can be reversed and so there is a one-to-one correspondence between the direct sum decomposition into ideals and the orthogonal central idempotents summing up to the unity 1. Also, each itself is a ring on its own right, the unity given by , and, as a ring, R is the product ring
For example, again take . This ring is a simple ring; in particular, it has no nontrivial decomposition into two-sided ideals.
Types of decomposition
There are several types of direct sum decompositions that have been studied:
Semisimple decomposition: a direct sum of simple modules.
Indecomposable decomposition: a direct sum of indecomposable modules.
A decomposition with local endomorphism rings (cf. #Azumaya's theorem): a direct sum of modules whose endomorphism rings are local rings (a ring is local if for each element x, either x or 1 − x is a unit).
Serial decomposition: a direct sum of uniserial modules (a module is uniserial if the lattice of submodules is a finite chain).
Since a simple module is indecomposable, a semisimple decomposition is an indecomposable decomposition (but not conversely). If the endomorphism ring of a module is local, then, in particular, it cannot have a nontrivial idempotent: the module is indecomposable. Thus, a decomposition with local endomorphism rings is an indecomposable decomposition.
A direct summand is said to be maximal if it admits an indecomposable complement. A decomposition is said to complement maximal direct summands if for each maximal direct summand L of M, there exists a subset such that
Two decompositions are said to be equivalent if there is a bijection such that for each , . If a module admits an indecomposable decomposition complementing maximal direct summands, then any two indecomposable decompositions of the module are equivalent.
Azumaya's theorem
In the simplest form, Azumaya's theorem states: given a decomposition such that the endomorphism ring of each is local (so the decomposition is indecomposable), each indecomposable decomposition of M is equivalent to this given decomposition. The more precise version of the theorem states: still given such a decomposition, if , then
if nonzero, N contains an indecomposable direct summand,
if is indecomposable, the endomorphism ring of it is local and is complemented by the given decomposition:
and so for some ,
for each , there exist direct summands of and of such that .
The endomorphism ring of an indecomposable module of finite length is local (e.g., by Fitting's lemma) and thus Azumaya's theorem applies to the setup of the Krull–Schmidt theorem. Indeed, if M is a module of finite length, then, by induction on length, it has a finite indecomposable decomposition , which is a decomposition with local endomorphism rings. Now, suppose we are given an indecomposable decomposition . Then it must be equivalent to the first one: so and for some permutation of . More precisely, since is indecomposable, for some . Then, since is indecomposable, and so on; i.e., complements to each sum can be taken to be direct sums of some 's.
Another application is the following statement (which is a key step in the proof of Kaplansky's theorem on projective modules):
Given an element , there exist a direct summand of and a subset such that and .
To see this, choose a finite set such that . Then, writing , by Azumaya's theorem, with some direct summands of and then, by modular law, with . Then, since is a direct summand of , we can write and then , which implies, since F is finite, that for some J by a repeated application of Azumaya's theorem.
In the setup of Azumaya's theorem, if, in addition, each is countably generated, then there is the following refinement (due originally to Crawley–Jónsson and later to Warfield): is isomorphic to for some subset . (In a sense, this is an extension of Kaplansky's theorem and is proved by the two lemmas used in the proof of the theorem.) According to , it is not known whether the assumption " countably generated" can be dropped; i.e., this refined version is true in general.
Decomposition of a ring
On the decomposition of a ring, the most basic but still important observation, known as the Wedderburn-Artin theorem is this: given a ring R, the following are equivalent:
R is a semisimple ring; i.e., is a semisimple left module.
for division rings , where denotes the ring of n-by-n matrices with entries in , and the positive integers , the division rings , and the positive integers are determined (the latter two up to permutation) by R
Every left module over R is semisimple.
To show 1. 2., first note that if is semisimple then we have an isomorphism of left -modules where are mutually non-isomorphic minimal left ideals. Then, with the view that endomorphisms act from the right,
where each can be viewed as the matrix ring over , which is a division ring by Schur's Lemma. The converse holds because the decomposition of 2. is equivalent to a decomposition into minimal left ideals = simple left submodules. The equivalence 1. 3. holds because every module is a quotient of a free module, and a quotient of a semisimple module is semisimple.
See also
Pure-injective module
Notes
References
Frank W. Anderson, Lectures on Non-Commutative Rings , University of Oregon, Fall, 2002.
Y. Lam, Bass's work in ring theory and projective modules [MR 1732042]
R. Warfield: Exchange rings and decompositions of modules, Math. Annalen 199(1972), 31–36.
Module theory | Decomposition of a module | Mathematics | 2,005 |
1,749,638 | https://en.wikipedia.org/wiki/Encyclopedia%20of%20World%20Problems%20and%20Human%20Potential | The Encyclopedia of World Problems and Human Potential (EWPHP) is a research work published by the Union of International Associations (UIA). It is available online since 2000, and was previously available as a CD-ROM and as a three-volume book.
The EWPHP began under the direction of Anthony Judge in 1972 and eventually came to comprise more than 100,000 entries and 700,000 links, as well as hundreds of pages of introductory notes and commentaries on problems, strategies, values, concepts of human development, and various intellectual resources.
Contributors and history
The project was originally conceived in 1972 by James Wellesley-Wesley, who provided financial support through the foundation Mankind 2000, and Anthony Judge, by whom the work was orchestrated.
Work on the first edition started with funds from Mankind 2000, matching those of the UIA. The publisher Klaus Saur, of Munich, provided funds, in conjunction with those from the UIA, for work on the 2nd, 3rd, and 4th editions. Seed funding for the third volume of the 4th edition was also provided on behalf of Mankind 2000. In the nineties, seed funding was provided, again on behalf of Mankind 2000, for computer equipment which subsequently allowed the UIA to develop a website and make available for free the 1994–1995 edition of the EWPHP databases. The UIA, on the initiative of Nadia McLaren, a consultant ecologist who has been a primary editor for the EWPHP, instigated two multi-partner projects funded by the European Union, with matching funds from the UIA. The work done through those two projects, Ecolynx: Information Context for Biodiversity Conservation (mainly) and Interactive Health Ecology Access Links, resulted in a fifth, web-based edition of the EWPHP in 2000. Two other individuals supported the project: Robert Jungk of Mankind 2000, and Christian de Laet of the UIA.
EWPHP began as a processing of documents gathered from entities profiled in the Yearbook of International Organizations. The United Nations Library in Geneva facilitated access to other material over two decades. At one point, the Institute of Cultural Affairs International was contractually associated. The Goals, Processes and Indicators of Development project was led by Johan Galtung of the United Nations University, in conjunction with Anthony Judge.
The principal editors of the EWPHP's editions have been Jon Jenkins, Maureen Jenkins, Owen Victor, Jacqueline Nebel, Nadia McLaren, and Tomáš Fülöpp. In 2005, following disagreement over the partnership contract, Anthony Judge, in his role as executive secretary of Mankind 2000, reframed the EWPHP as having been a strategic initiative of the Union of Intelligible Associations.
Tomáš Fülöpp maintained the EWPHP databases at the UIA until sometime after January 2012. Tomáš Fülöpp also acts as manager along with senior editors Nadia McLaren and Kimberly Trathen.
Editions
The 1st edition, initiated in 1972 and published in 1976, has one volume entitled Yearbook of World Problems and Human Potential, comprising thirteen sections, several of which have not appeared in subsequent editions.
The 2nd edition, initiated in 1983 and published in 1986, was titled Encyclopedia of World Problems and Human Potential. It is still a single volume (published as volume 4 of the Yearbook of International Organizations), but with different sections due to the variegated types of paper used in printing the edition. The book is equivalent to several normal volumes. According to Edward Cornish of The Futurist, one such book is equivalent to 40 or 50 normal-sized books.
The 3rd edition, initiated in 1988 and published in 1991, has two volumes: World Problems (vol. 1), and Human Potential (vol. 2).
The 4th edition, initiated in 1992 and again in 1994–1995, has three volumes: World Problems (vol. 1), Human Potential – Transformation and Values (vol.2), Actions – Strategies – Solutions (vol. 3). A CD-ROM version, Encyclopedia Plus, is also published.
The online edition was initiated in 1997 and completed in 2000.
Critical reception
There have been several reviews of the EWPHP. One of the criticisms came from the American Library Association in 1987: "The board considers the Encyclopedia of World Problems and Human Potential a problematic monument to idiosyncrasy, confusion, and obfuscation that certainly is not worth purchasing at any price." Similarly, The Guardian was critical in a review article published in 1992. The Wall Street Journal published a review of the EWPHP initiative in December 2012.
See also
Decision making
Environmental issue
Global governance
Policy
Political issue
Problem solving
Public policy
Social issue
Wicked problem
References
External links
Encyclopedia of World Problems and Human Potential (main database)
Encyclopedia of World Problems and Human Potential (editing platform)
Encyclopedia of World Problems and Human Potential (project information)
Ecolynx - A short movie exemplifying the use of the EWPHP
Encyclopedia of World Problems Has a Big One of Its Own, a Wall Street Journal article, 11 December 2012.
Union of International Associations
Online encyclopedias
Online databases
Public policy
Social issues
Economic problems
Problem solving
Global issues
Human development | Encyclopedia of World Problems and Human Potential | Biology | 1,047 |
1,468,408 | https://en.wikipedia.org/wiki/Guaco | Guaco, huaco, vejuco and bejuco are terms applied to various vine-like Central American, South American, and West Indian climbing plants, reputed to have curative powers. Several species in the genus Mikania are among those referred to as guaco. Even though it is not a vine guaco is also used to refer to Cleome serrulata, the Rocky Mountain beeplant.
Native Americans and Colombians believe that the guaco was named after a species of kite, in imitation of its cry, which they say it uses to attract the snakes which it feeds on. Tradition says that the plant's powers as an antidote were discovered through watching the bird eat the leaves, and even spread the juice on its wings, before attacking the snakes.
Any twining plant with a heart-shaped leaf, white and green above and purple beneath, is called a guaco by Native Americans, which does not necessarily coincide with which plants are "true" guacos, as far as naturalists are concerned.
What is most commonly recognized in Colombia as guaco, or vejuco del guaco, would appear to be Mikania guaco, a climbing composite plant of the tribe Eupatorieae, preferring moist and shady situations, and having a much-branched and deep-growing root, variegated, serrated, opposite leaves and dull white flowers, in axillary clusters. The whole plant emits a disagreeable odour.
Uses
It was stated that the Central American natives, after taking guaco, catch with impunity the most dangerous snakes, which writhe in their hands as though touched by a hot iron. The odour alone of guaco, has been said to cause, in snakes, a state of stupor; and Humboldt, who observed that proximity of a rod steeped in guaco-juice was obnoxious to the venomous Coluber corallinus, was of the opinion that inoculation with it gives perspiration an odour which makes reptiles unwilling to bite. The drug is not used in modern medicine.
In Brazil, guaco (Mikania glomerata) is commonly used as a medicinal tea as an expectorant and anti-inflammatory due to its compound coumarin.
Notes
References
Medicinal plants
Flora of Colombia
Natural history of Colombia
Plant common names
Mikania | Guaco | Biology | 487 |
21,799,992 | https://en.wikipedia.org/wiki/Peace%20ecology | The term peace ecology has been used by Christos Kyrou of American University to describe a proposed theoretical framework that is intended to provide "a better understanding, of the inherent capacities of the environment to inform and sustain peace."
Use of the term
Peace ecology was introduced by Professor Christos Kyrou, of American University first in an article at the annual meeting of the International Studies Association, in San Diego, California, Mar 22, 2006. It was later published in its completed form in an article with the title Peace Ecology: An Emerging Paradigm In Peace Studies in The International Journal of Peace Studies, Volume 12 #1, 2007.
With a follow-up article submitted for the Conference on Cutting Edge Theories and Recent Developments in Conflict Resolution, September 27 and 28, 2007, at Syracuse, NY, Dr. Kyrou examined various methodological perspectives from Peace Ecology.
Dr. Kyrou, together with his graduate and undergraduate students at the International Peace & Conflict Resolution Division of the School of International Service at The American University in Washington DC continue their effort to expand the practical and theoretical potential of Peace Ecology.
References
External links
Home page of Christos Kyrou
Ecology
Theories | Peace ecology | Biology | 233 |
51,008,352 | https://en.wikipedia.org/wiki/Hydrodynamic%20scour | Hydrodynamic scour is the removal of sediment such as silt, sand and gravel from around the base of obstructions to the flow in the sea, rivers and canals. Scour, caused by fast flowing water, can carve out scour holes, compromising the integrity of a structure. It is an interaction between the hydrodynamics and the geotechnical properties of the substrate. It is a notable cause of bridge failure and a problem with most marine structures supported by the seabed in areas of significant tidal and ocean current. It can also affect biological ecosystems and heritage assets.
Mechanism
Any obstruction within flowing water will produce changes in velocity within the water column. The flow changes that occur in the vicinity of the substrate may cause differential movement in the bed materials near the obstruction. The magnitude of these changes varies with stream velocity, feature shape and substrate character. Generally the stream bed is deepened at the upstream end of the obstruction, and the material removed from the substrate is usually deposited in the sheltered areas behind or adjacent to the obstruction where the local velocity is sufficiently reduced. In conditions of high stream velocities, mobile bed materials, and poorly streamlined structures scour depths can be quite deep.
See also
Bridge scour
Tidal scour
Kolk_(vortex)
References
Erosion
Fluvial geomorphology
Hydraulic_engineering | Hydrodynamic scour | Physics,Engineering,Environmental_science | 272 |
7,266,679 | https://en.wikipedia.org/wiki/Bedford%20Level%20experiment | The Bedford Level experiment was a series of observations carried out along a length of the Old Bedford River on the Bedford Level of the Cambridgeshire Fens in the United Kingdom during the 19th and early 20th centuries to deny the curvature of the Earth through measurement.
Samuel Birley Rowbotham, who conducted the first observations starting in 1838, claimed that he had proven the Earth to be flat. However, in 1870, after adjusting Rowbotham's method to allow for the effects of atmospheric refraction, Alfred Russel Wallace found a curvature consistent with a spherical Earth.
The Bedford Level
At the point chosen for all the experiments, the river is a slow-flowing drainage canal running in an uninterrupted straight line for a stretch to the north-east of the village of Welney. This makes it an ideal location to directly measure the curvature of the Earth, as Rowbotham wrote in Zetetic Astronomy:
Experiments
The first experiment at this site was conducted by Rowbotham in the summer of 1838. He waded into the river and used a telescope held above the water to watch a boat, with a flag on its mast above the water, row slowly away from him. He reported that the vessel remained constantly in his view for the full to Welney Bridge, whereas, had the water surface been curved with the accepted circumference of a spherical Earth, the top of the mast should have been about below his line of sight. He published this observation using the pseudonym Parallax in 1849 and subsequently expanded it into a book, Earth Not a Globe published in 1865.
Rowbotham repeated his experiments several times over the years, but his claims received little attention until, in 1870, a supporter by the name of John Hampden offered a wager that he could show, by repeating Rowbotham's experiment, that the Earth was flat. The naturalist and qualified surveyor Alfred Russel Wallace accepted the wager. Wallace, by virtue of his surveyor's training and knowledge of physics, avoided the errors of the preceding experiments and won the bet.
The crucial steps were:
To set a sight line above the water, and thereby reduce the effects of atmospheric refraction.
To add a pole in the middle of the length of canal that could be used to see the "bump" caused by the curvature of the Earth between the two end points.
Despite Hampden initially refusing to accept the demonstration, Wallace was awarded the bet by the referee, John Henry Walsh, editor of The Field sports magazine.
Hampden subsequently published a pamphlet alleging that Wallace had cheated, and sued for his money. Several protracted court cases ensued, with the result that Hampden was imprisoned for threatening to kill Wallace and for libel.
The same court ruled that the wager had been invalid because Hampden retracted the bet and required that Wallace return the money to Hampden.
Wallace, who had been unaware of Rowbotham's earlier experiments, was criticized by his peers for "his 'injudicious' involvement in a bet to 'decide' the most fundamental and established of scientific facts".
In 1901, Henry Yule Oldham, a reader in geography at King's College, Cambridge, reproduced Wallace's results using three poles fixed at equal height above water level. When viewed through a theodolite, the middle pole was found to be about higher than the poles at each end. This version of the experiment was taught in schools in England until photographs of the Earth from space became available, and it remains in the syllabus for the Indian Certificate of Secondary Education for 2023.
On 11 May 1904 Lady Elizabeth Anne Blount, who was later influential in the formation of the Flat Earth Society, hired a commercial photographer to use a telephoto-lens camera to take a picture from Welney of a large white sheet she had placed, the bottom edge near the surface of the river, at Rowbotham's original position away. The photographer, Edgar Clifton from Dallmeyer's studio, mounted his camera above the water at Welney and was surprised to be able to obtain a picture of the target, which he believed should have been invisible to him, given the low mounting point of the camera. Lady Blount published the pictures far and wide.
These controversies became a regular feature in the English Mechanic magazine in 1904–05, which published Blount's photo and reported two experiments in 1905 that showed the opposite results. One of these, by Clement Stretton conducted on the Ashby Canal, mounted a theodolite on the canal bank aligned with the cabin roof of a boat. When the boat had moved one mile distant, the instrument showed a dip from the sight-line of about eight inches.
Refraction
Atmospheric refraction can produce the results noted by Rowbotham and Blount. Because the density of air in the Earth's atmosphere decreases with height above the Earth's surface, all light rays travelling nearly horizontally bend downward, so that the line of sight is a curve. This phenomenon is routinely accounted for in levelling and celestial navigation.
If the measurement is close enough to the surface, this downward curve may match the mean curvature of the Earth's surface. In this case, the two effects of assumed curvature and refraction could cancel each other out, and the Earth will then appear flat in optical experiments.
This would have been aided, on each occasion, by a temperature inversion in the atmosphere with temperature increasing with altitude above the canal, similar to the phenomenon of the superior image mirage. Temperature inversions like this are common. An increase in air temperature or lapse rate of 0.11 Celsius degrees per metre of altitude would create an illusion of a flat canal, and all optical measurements made near ground level would be consistent with a completely flat surface. If the lapse rate were higher than this (temperature increasing with height at a greater rate), all optical observations would be consistent with a concave surface, a "bowl-shaped Earth". Under average conditions, optical measurements are consistent with a spherical Earth approximately 15% less curved than in reality. Repetition of the atmospheric conditions required for each of the many observations is not unlikely, and warm days over still water can produce favourable conditions.
Similar experiments conducted elsewhere
On 25 July 1896, Ulysses Grant Morrow, a newspaper editor, conducted a similar experiment on the Old Illinois Drainage Canal, Summit, Illinois. Unlike Rowbotham, he was seeking to demonstrate that the surface of the Earth was curved: when he too found that his target marker, above water level and distant, was clearly visible, he concluded that the Earth's surface was concavely curved, in line with the expectations of his sponsors, the Koreshan Unity society. The findings were dismissed by critics as the result of atmospheric refraction.
See also
History of geodesy
Notes
References
History of geography
History of Earth science
Earth sciences
Physics experiments
Flat Earth
Geodesy
History of measurement | Bedford Level experiment | Physics,Mathematics | 1,415 |
1,680,877 | https://en.wikipedia.org/wiki/Air%20filter | A particulate air filter is a device composed of fibrous, or porous materials which removes particulates such as smoke, dust, pollen, mold, viruses and bacteria from the air. Filters containing an adsorbent or catalyst such as charcoal (carbon) may also remove odors and gaseous pollutants such as volatile organic compounds or ozone. Air filters are used in applications where air quality is important, notably in building ventilation systems and in engines.
Some buildings, as well as aircraft and other human-made environments (e.g., satellites, and Space Shuttles) use foam, pleated paper, or spun fiberglass filter elements. Another method, air ionizers, use fibers or elements with a static electric charge, which attract dust particles. The air intakes of internal combustion engines and air compressors tend to use either paper, foam, or cotton filters. Oil bath filters have fallen out of favour aside from niche uses. The technology of air intake filters of gas turbines has improved significantly in recent years, due to improvements in the aerodynamics and fluid dynamics of the air-compressor part of the gas turbines.
HEPA filters
High efficiency particulate arrester (HEPA), originally called high-efficiency particulate absorber but also sometimes called high-efficiency particulate arresting or high-efficiency particulate arrestance, is a type of air filter. Filters meeting the HEPA standard have many applications, including use in clean rooms for IC fabrication, medical facilities, automobiles, aircraft and homes. The filter must satisfy certain standards of efficiency such as those set by the United States Department of Energy (DOE).
Varying standards define what qualifies as a HEPA filter. The two most common standards require that an air filter must remove (from the air that passes through) 99.95% (European Standard) or 99.97% (ASME standard) of particles that have a size greater than or equal to 0.3 μm.
Automotive cabin air filters
The cabin air filter, also known in the United Kingdom as a pollen filter, is typically a pleated-paper filter that is placed in the outside-air intake for the vehicle's passenger compartment. Some of these filters are rectangular and similar in shape to the engine air filter. Others are uniquely shaped to fit the available space of particular vehicles' outside-air intakes.
The first automaker to include a disposable filter to keep the ventilation system clean was the Nash Motors "Weather Eye", introduced in 1940.
A reusable heater core filter was available as an optional accessory on Studebaker models beginning in 1959, including Studebaker Lark automobiles (1959-1966), Studebaker Gran Turismo Hawk automobiles (1962-1964) and Studebaker Champ trucks (1960-1964). The filter was an aluminum frame containing an aluminum mesh and was located directly above the heater core. The filter was removed and installed from the engine compartment through a slot in the firewall. A long, thin rubber seal plugged the slot when the filter was installed. The filter could be vacuumed and washed prior to installation.
Clogged or dirty cabin air filters can significantly reduce airflow from the cabin vents, as well as introduce allergens into the cabin air stream. Since the cabin air temperature depends upon the flow rate of the air passing through the heater core, the evaporator, or both, clogged filters can greatly reduce the effectiveness and performance of the vehicle's air conditioning and heating systems.
Some cabin air filters perform poorly, and some cabin air filter manufacturers do not print a minimum efficiency reporting value (MERV) filter rating on their cabin air filters.
Internal combustion engine air filters
The combustion air filter prevents abrasive particulate matter from entering the engine's cylinders, where it would cause mechanical wear and oil contamination.
Most fuel injected vehicles use a pleated paper filter element in the form of a flat panel. This filter is usually placed inside a plastic box connected to the throttle body with duct work. Older vehicles that use carburetors or throttle body fuel injection typically use a cylindrical air filter, usually between and in diameter. This is positioned above or beside the carburetor or throttle body, usually in a metal or plastic container which may incorporate ducting to provide cool and/or warm inlet air, and secured with a metal or plastic lid. The overall unit (filter and housing together) is called the air cleaner.
Paper
Pleated paper filter elements are the nearly exclusive choice for automobile engine air cleaners, because they are efficient, easy to service, and cost-effective. The "paper" term is somewhat misleading, as the filter media are considerably different from papers used for writing or packaging, etc. There is a persistent belief among tuners, fomented by advertising for aftermarket non-paper replacement filters, that paper filters flow poorly and thus restrict engine performance. In fact, as long as a pleated-paper filter is sized appropriately for the airflow volumes encountered in a particular application, such filters present only trivial restriction to flow until the filter has become significantly clogged with dirt. Construction equipment engines also use this. The reason is that the paper is bent in zig-zag shape, and the total area of the paper is very large, in the range of 50 times of the air opening.
Foam
Oil-wetted polyurethane foam elements are used in some aftermarket replacement automobile air filters. Foam was in the past widely used in air cleaners on small engines on lawnmowers and other power equipment, but automotive-type paper filter elements have largely supplanted oil-wetted foam in these applications. Foam filters are still commonly used on air compressors for air tools up to . Depending on the grade and thickness of foam employed, an oil-wetted foam filter element can offer minimal airflow restriction or very high dirt capacity, the latter property making foam filters a popular choice in off-road rallying and other motorsport applications where high levels of dust will be encountered. Due to the way dust is captured on foam filters, large amounts may be trapped without measurable change in airflow restriction.
Cotton
Oiled cotton gauze is employed in a growing number of aftermarket automotive air filters marketed as high-performance items. In the past, cotton gauze saw limited use in original-equipment automotive air filters. However, since the introduction of the Abarth SS versions, the Fiat subsidiary supplies cotton gauze air filters as OE filters.
Stainless steel
Stainless steel mesh is another example of medium which allow more air to pass through.
Stainless steel mesh comes with different mesh counts, offering different filtration standards.
In an extreme modified engine lacking in space for a cone based air filter, some will opt to install a simple stainless steel mesh over the turbo to ensure no particles enter the engine via the turbo.
Oil bath
An oil bath air cleaner consists of a sump containing a pool of oil, and an insert which is filled with fiber, mesh, foam, or another coarse filter media. The cleaner removes particles by adhering them to the oil-soaked filter media rather than traditional filtration, the openings in the filter media are much larger than the particles that are to be filtered. When the cleaner is assembled, the media-containing body of the insert sits a short distance above the surface of the oil pool. The rim of the insert overlaps the rim of the sump. This arrangement forms a labyrinthine path through which the air must travel in a series of U-turns: up through the gap between the rims of the insert and the sump, down through the gap between the outer wall of the insert and the inner wall of the sump, and up through the filter media in the body of the insert. This U-turn takes the air at high velocity across the surface of the oil pool. Larger and heavier dust and dirt particles in the air cannot make the turn due to their inertia, so they fall into the oil and settle to the bottom of the base bowl. Lighter and smaller particles stick to the filtration media in the insert, which is wetted by oil droplets aspirated there into by normal airflow. The constant aspiration of oil onto the filter media slowly carries most of the finer trapped particles downward and the oil drips back into the reservoir where the particles accumulate.
Oil bath air cleaners were very widely used in automotive and small engine applications until the widespread industry adoption of the paper filter in the early 1960s. Such cleaners are still used in off-road equipment where very high levels of dust are encountered, for oil bath air cleaners can sequester a great deal of dirt relative to their overall size without loss of filtration efficiency or airflow. However, the liquid oil makes cleaning and servicing such air cleaners messy and inconvenient, they must be relatively large to avoid excessive restriction at high airflow rates, and they tend to increase exhaust emissions of unburned hydrocarbons due to oil aspiration when used on spark-ignition engines.
Water bath
In the early 20th century (about 1900 to 1930), water bath air cleaners were used in some applications (cars, trucks, tractors, and portable and stationary engines). They worked on roughly the same principles as oil bath air cleaners. For example, the original Fordson tractor had a water bath air cleaner. By the 1940s, oil bath designs had displaced water bath designs because of better filtering performance.
Bulk solids handling filters
Bulk solids handling involves the transport of solids (mechanical transport, pneumatic transport) which may be in a powder form. Many industries are handling bulk solids (mining industries, chemical industries, food industries) which requires the treatment of air streams escaping the process so that fine particles are not emitted, for regulatory reasons or economical reasons (loss of materials). As a consequence, air filters are positioned at many places in the process, especially at the reception of pneumatic conveying lines where the quantity of air is important and the load in fine particle quite important. Filters can also be placed at any point of air exchange in the process to avoid that pollutants enter the process, which is particularly true in pharmaceuticals and food industries. The physical phenomena involved in catching particles with a filter are mainly inertial and diffusional
Filter classes
Under European normalization standards EN 779, the following filter classes were recognized:
European standard EN 779, on which the above table is based, remained in effect from 2012 to mid-2018, when it was replaced by ISO 16890.
See also
Air purifier
Clean Air Delivery Rate
CityTrees
Corsi–Rosenthal Box
Cyclonic separation
Dehumidifier
Diesel particulate filter
Dust collector
Humidifier
Impingement filter
Indoor air quality
Mechanical filter (respirator)#Filtration standards
Nose filter
Oil filter
Pocket filter
Respirator
Scrubber
Smog tower
Swan neck duct
Wikipedia:Edit filter
References
External links
Auto parts
Air filters
Particulate control
Engine components
Gas technologies
Solid-gas separation
ja:エアクリーナー | Air filter | Chemistry,Technology | 2,262 |
742,319 | https://en.wikipedia.org/wiki/Faraday%27s%20laws%20of%20electrolysis | Faraday's laws of electrolysis are quantitative relationships based on the electrochemical research published by Michael Faraday in 1833.
First law
Michael Faraday reported that the mass () of a substance deposited or liberated at an electrode is directly proportional to the charge (, for which the SI unit is the ampere-second or coulomb).
Here, the constant of proportionality, , is called the electro-chemical equivalent (ECE) of the substance. Thus, the ECE can be defined as the mass of the substance deposited or liberated per unit charge.
Second law
Faraday discovered that when the same amount of electric current is passed through different electrolytes connected in series, the masses of the substances deposited or liberated at the electrodes are directly proportional to their respective chemical equivalent/equivalent weight (). This turns out to be the molar mass () divided by the valence ()
Derivation
A monovalent ion requires one electron for discharge, a divalent ion requires two electrons for discharge and so on. Thus, if electrons flow, atoms are discharged.
Thus, the mass discharged is
where
is the Avogadro constant;
is the total charge, equal to the number of electrons () times the elementary charge ;
is the Faraday constant.
Mathematical form
Faraday's laws can be summarized by
where is the molar mass of the substance (usually given in SI units of grams per mole) and is the valency of the ions .
For Faraday's first law, are constants; thus, the larger the value of , the larger will be.
For Faraday's second law, are constants; thus, the larger the value of (equivalent weight), the larger will be.
In the simple case of constant-current electrolysis, , leading to
and then to
where:
is the amount of substance ("number of moles") liberated:
is the total time the constant current was applied.
For the case of an alloy whose constituents have different valencies, we have
where represents the mass fraction of the th element.
In the more complicated case of a variable electric current, the total charge is the electric current integrated over time :
Here is the total electrolysis time.
Applications
Electroplating – a process where a thin layer of metal is deposited onto the surface of an object using an electric current
Electrochemical cells – generates electrical energy from chemical reactions
Electrotyping – a process used to create metal copies of designs by depositing metal onto a mold using electroplating
Electrowinning – a process that extract metals from their solutions using an electric current
Electroforming – a process that deposits metal onto a mold or substrate to create metal parts
Anodization – a process that converts the surface of a metal into a durable corrosion-resistant oxide layer
Conductive polymers – organic polymers that conduct electricity
Water electrolysis – a process that uses an electric current to split water molecules into hydrogen and oxygen gases
Electrolytic capacitors – a type of capacitor that uses an electrolytic solution as one of its plates
See also
Electrolysis
Faraday's law of induction
Tafel equation
References
Further reading
Serway, Moses, and Moyer, Modern Physics, third edition (2005), principles of physics.
Experiment with Faraday's laws
Electrochemistry
Electrolysis
Electrochemical equations
Scientific laws
Michael Faraday | Faraday's laws of electrolysis | Chemistry,Mathematics | 678 |
52,701,677 | https://en.wikipedia.org/wiki/Tom%20Voltaire%20Okwalinga | Tom Voltaire Okwalinga also known as TVO is an anonymous Ugandan and famous social media critique of the Uganda's government.
He has been leaking a series of the Uganda's government secrets through his Facebook account for which he has over 120,000 followers.
In April 2014, he posted a secret tape that implicated the Inspector General of Police (IGP) of the Uganda Police Force then, Kale Kayihura’s attempt to investigate and curtail Amama Mbabazi’s underneath campaign to oust President Museveni in the 2016 presidential elections.
No one knows the true identity of TVO including his many followers and Facebook refused to reveal his identity to the Uganda government.
References
Year of birth missing (living people)
Living people
People in information technology
Ugandan activists
Ugandan bloggers | Tom Voltaire Okwalinga | Technology | 166 |
35,863,555 | https://en.wikipedia.org/wiki/AIR%20Shipper | The AIR Shipper is a regulatory manual utilized by air shippers for shipping dangerous goods. A.I.R. Shipper is the first regulations publication recognized by the International Civil Aviation Organization and is developed in compliance with ICAO standards. A.I.R. Shipper is published by Labelmaster, a U.S.-based manufacturer of regulatory compliance products.
See also
List of UN numbers
Packaging and labeling
Packing groups
UN Recommendations on the Transport of Dangerous Goods
References
Safety
Hazardous materials | AIR Shipper | Physics,Chemistry,Technology | 99 |
15,840,012 | https://en.wikipedia.org/wiki/Optical%20pulsar | An optical pulsar is a pulsar which can be detected in the visible spectrum. There are very few of these known: the Crab Pulsar was detected by stroboscopic techniques in 1969, shortly after its discovery in radio waves, at the Steward Observatory. The Vela Pulsar was detected in 1977 at the Anglo-Australian Observatory, and was the faintest star ever imaged at that time.
Six known optical pulsars are listed by Shearer and Golden (2002):
References
External links
"A Pulsar Discovery: First Optical Pulsar." Moments of Discovery, American Institute of Physics, 2007 (Includes audio and teachers guides).
Star types | Optical pulsar | Astronomy | 142 |
78,230,327 | https://en.wikipedia.org/wiki/Sheng%20%28volume%29 | The Chinese sheng (), called sho in Japan and seung in Korea, also called Chinese liter, is a traditional unit of volume in East Asia. It originated from China and later spread to Japan, the Korean Peninsula, Vietnam and other places. One sheng equals 10 ge or 1/10 dou, though its specific capacity has varied by times and regions. Nowadays, 1 sheng is 1 liter in China, 1.8039 liters in Japan and 1.8 liters in Korea.
Sheng is a traditional measure for cereal grains. Now, like "liter", sheng is more often used to measure liquid or gas.
Ancient systems
As a unit of volume, sheng appeared in the Warring States Period (c. 475 to 221 BC) of China and has remained in use ever since.
Sheng and the other units of volume were usually used to measure cereal grains in ancient China.
Modern systems
China
Sheng is the basic unit in the volume system promulgated by the Chinese government in 1915. One sheng (升) equals 1.0354688 liters.
The following table is based on the "Weights and Measures Acts" of the 18th year of the Republic of China (1929), which came into effect on January 1, 1930. The Chinese volume units listed in the "Chinese Name Plan for Unified Metric Units of Measurement" of the People's Republic of China in 1959 are Chinese dan, dou, sheng, and ge.
The basic unit remains sheng, and one sheng is equal to one liter. The Chinese sheng is also called "市升" ("market sheng" or "market liter") to distinguish from the Chinese translation of "liter", which is called "公升", ("common sheng" or "common liter").
Nowadays, like the unit of "liter", sheng is more often used to measure liquid or gas.
Japan
The base unit of volume in Japan is shō (), i.e., the Japanese sheng. One sho equals 1.804 liters. Sake and shochu are both commonly sold in large 1800mL bottles known as , literally "one shō bottle".
Korea
The base unit of Korean volume is the doi, equal to the Korean sheng (seung, 승(升)).
Sheng and Liter
The English "liter" is also called sheng (升) in China. In the cases where distinguishing is needed, word "liter" is translated into 公升 ("common sheng", or "common liter"), and the traditional Chinese sheng is called 市升 ("market sheng", or "market liter"), because it is more frequently used in the market.
The shengs can also be distinguished by the regions they were defined, such as the "Chinese sheng", "Japanese shō", "Korean seung", "British liter", etc.
In China, one sheng is equal to one liter. Since the two units are of the same size, they are both called sheng in Chinese or "liter" in English for short when distinction is not necessary.
In addition, the Chinese standard SI prefixes may be added to 升 (shēng) to form more units, such as 分升(fensheng, deciliter, dl), 厘升 (lisheng, centiliter, cl), 毫升 (haosheng, milliliter, cl).
See also
Chinese units of measurement
Japanese units of measurement
Korean units of measurement
:zh:中國度量衡
Notes
References
Units of volume
Customary units of measurement | Sheng (volume) | Mathematics | 725 |
28,296,197 | https://en.wikipedia.org/wiki/Asset%20integrity%20management%20systems | Asset Integrity Management Systems (AIMS) outline the ability of an asset to perform its required function effectively and efficiently whilst protecting health, safety and the environment and the means of ensuring that the people, systems, processes, and resources that deliver integrity are in place, in use and will perform when required over the whole life-cycle of the asset. The technical aspects of AIMS are illustrated in Figure 1. Originally developed in the UK, Asset Integrity Management was the result of a collaboration between the HSE and leading oil and gas operators resulting in a series of reports (Belfry Report) and workshops, the outcome being a group of documents called Key Programmes (KP Series), currently publicly available.
An Integrity Management System should address the quality at every stage of the asset life cycle, from the design of new facilities to maintenance management to decommissioning. Inspections, auditing/assurance and overall quality processes are just some of the tools designed to make an integrity management system effective.
Under the operational phase of the life cycle, the asset integrity, for example in the oil and gas industry can be divided into disciplines based on equipment categories:
Static equipment integrity
Rotating equipment/machinery integrity
Electrical equipment integrity
Instrument and control equipment integrity
Structural integrity
Pipeline integrity
Well integrity
Evacuation and rescue system integrity
The AIMS should also endeavour to maintain the asset in a fit-for-service condition while extending its remaining life in the most reliable, safe, and cost-effective manner. The AIM programs (in the US) attempt to meet API-580, API-581, and PAS 55 requirements, as applicable. (However local legal requirements may differ, please refer to a competent, experienced local professional for advice).
The AIMS document will stipulate the requirements for subsequent Integrity Management Plans.
Asset Integrity management improves plant reliability and safety whilst reducing unplanned maintenance and repair costs.
But an asset integrity management system does not exist in isolation. In order to successfully implement an asset integrity management system in a dynamic operating environment, it is essential that all stakeholders have a consistent and a unified understanding of what the essentials of asset integrity are and how they can be applied in their day-to-day operations, yet this is often cited as among the most significant challenges in achieving an integrity culture within an organisation.
Literature
Development of plans to ensure the long-term integrity of a pipeline or pipeline system
Integrity Management Plan, Sunoco Pipeline, L.P.
Pipeline Integrity Management Plan: Atlanta Gas and Light
Department of Transportation: Pipeline and Hazardous Materials Safety Administration 49 CFR Parts 192 and 195 (Docket No. RSPA–04–16855; Amdt. 192–101 and 195–85) Federal Register /Vol. 70, No. 205 /Tuesday, October 25, 2005 /Rules and Regulations
Asset Integrity Engineering
Key Programmes
External links
Oil and Gas Fundamentals The Fundamentals of Asset Integrity
Egan, F. Responsibilities in Asset Integrity Management
References
Asset management
Maintenance
Process safety | Asset integrity management systems | Chemistry,Engineering | 593 |
30,856,576 | https://en.wikipedia.org/wiki/Barcha | A barcha, barsha or brchha is a type of lance with a wooden handle, once common in South Asia (the word itself is Hindi). They were common in the 16th century.
Use in combat
The weapon found itself very handy with the emerging Marathas in the early seventeenth century. It was lighter to carry in the mountainous terrain and easier to manufacture. A skilled spearman (bhalaeet) could keep a heavily armed foot soldier at bay. With his slashing and thrusting motions, he could inflict much damage while surrounded by a number of swordsmen. The illustrious use of this weapon is recorded in the last stages of Third Battle of Panipat by the Maratha general Sadashivrao Bhau. Another version of this weapon is the ballam, a javelin effectively used to bring down infantry and cavalrymen at a distance.
Use in magic
The barcha is also considered a magical weapon used in a shaman's education. Along with purbe, a wooden ritual knife, and thudung, a drum, the lance was taught to the guru's student through participation in rituals. Variations of the barcha include the snake-like Nagini Barcha and the hand-shaped Karpa Barcha. Nagini Barcha was identified as the weapon used by the Sikh warrior Bachittar Singh during the siege of Lohgarh.
See also
Bagh nakh
Chakram
Katar
Trishula
References
Bibliography
Balfour, Edward (1885). The Cyclopædia of India and of Eastern and Southern Asia. London: Bernard Quaritch.
Mayaram, Shail (2003). Against History, Against State: Counterperspectives from the Margins. New York: Columbia University Press.
16th-century introductions
Lance
Indian martial arts
Weapons of India
Magic items | Barcha | Physics | 373 |
36,118,645 | https://en.wikipedia.org/wiki/Kosmos%201247 | Kosmos 1247 ( meaning Cosmos 1247) was a Soviet US-K missile early warning satellite which was launched in 1981 as part of the Soviet military's Oko programme. The satellite was designed to identify missile launches using optical telescopes and infrared sensors.
Kosmos 1247 was launched from Site 16/2 at Plesetsk Cosmodrome in the Russian SSR. A Molniya-M carrier rocket with a 2BL upper stage was used to perform the launch, which took place at 10:00 UTC on 19 February 1981. The launch successfully placed the satellite into a molniya orbit. It subsequently received its Kosmos designation, and the international designator 1981-016A. The United States Space Command assigned it the Satellite Catalog Number 12303.
Kosmos 1247 was a US-K satellite like Kosmos 862 that NASA believes deliberately self-destructed in orbit. It was observed to have
completed the first burn in a 2-phase maneuver sequence on 20 October 1981, followed by debris generation. All but one of the resultant debris pieces are still in orbit.
See also
1981 in spaceflight
List of Kosmos satellites (1251–1500)
List of Oko satellites
List of R-7 launches (1980-1984)
References
Kosmos satellites
Oko
Spacecraft launched in 1981
Spacecraft launched by Molniya-M rockets
Spacecraft that broke apart in space | Kosmos 1247 | Technology | 289 |
2,347,000 | https://en.wikipedia.org/wiki/Ancient%20Mesopotamian%20units%20of%20measurement | Ancient Mesopotamian units of measurement originated in the loosely organized city-states of Early Dynastic Sumer. Each city, kingdom and trade guild had its own standards until the formation of the Akkadian Empire when Sargon of Akkad issued a common standard. This standard was improved by Naram-Sin, but fell into disuse after the Akkadian Empire dissolved. The standard of Naram-Sin was readopted in the Ur III period by the Nanše Hymn which reduced a plethora of multiple standards to a few agreed upon common groupings. Successors to Sumerian civilization including the Babylonians, Assyrians, and Persians continued to use these groupings. Akkado-Sumerian metrology has been reconstructed by applying statistical methods to compare Sumerian architecture, architectural plans, and issued official standards such as Statue B of Gudea and the bronze cubit of Nippur.
Archaic system
The systems that would later become the classical standard for Mesopotamia were developed in parallel with writing in Sumer during Late Uruk Period (c. 3500–3000). Studies of protocuneiform indicate twelve separate counting systems used in Uruk IV-III. Seven of these were also used in the contemporary Proto-Elamite writing system. The bisexagesimal systems went out of use after the Early Dynastic I/II period.
Sexagesimal System S used to count slaves, animals, fish, wooden objects, stone objects, containers.
Sexagesimal System S' used to count dead animals, certain types of beer
Bisexagesimal System B used to count cereal, bread, fish, milk products
Bisexagesimal System B* used to count rations
GAN2 System G used to count field measurement
ŠE system Š used to count barley by volume
ŠE system Š' used to count malt by volume
ŠE system Š" used to count wheat by volume
ŠE System Š* used to count barley groats
EN System E used to count weight
U4 System U used to count calendrics
DUGb System Db used to count milk by volume
DUGc System Db used to count beer by volume
In Early Dynastic Sumer (–2300 BCE) metrology and mathematics were indistinguishable and treated as a single scribal discipline. The idea of an abstract number did not yet exist, thus all quantities were written as metrological symbols and never as numerals followed by a unit symbol. For example there was a symbol for one-sheep and another for one-day but no symbol for one. About 600 of these metrological symbols exist, for this reason archaic Sumerian metrology is complex and not fully understood. In general however, length, volume, and mass are derived from a theoretical standard cube, called 'gur (also spelled kor in some literature)', filled with barley, wheat, water, or oil. However, because of the different specific gravities of these substances combined with dual numerical bases (sexagesimal or decimal), multiple sizes of the gur-cube were used without consensus. The different gur-cubes are related by proportion, based on the water gur-cube, according to four basic coefficients and their cubic roots. These coefficients are given as:
Komma = correction when planning rations with a 360-day year
Leimma = conversion from decimal to a sexagesimal number system
Diesis =
Euboic =
One official government standard of measurement of the archaic system was the Cubit of Nippur (2650 BCE). It is a Euboic Mana + 1 Diesis (432 grams). This standard is the main reference used by archaeologists to reconstruct the system.
Classical system
A major improvement came in 2150 BCE during the Akkadian Empire under the reign of Naram-Sin when the competing systems were unified by a single official standard, the royal gur-cube. His reform is considered the first standardized system of measure in Mesopotamia. The royal gur-cube (Cuneiform: LU2.GAL.GUR, ; Akkadian: šarru kurru) was a theoretical cuboid of water approximately 6 m × 6 m × 0.5 m from which all other units could be derived. The Neo-Sumerians continued use of the royal gur-cube as indicated by the Letter of Nanse issued in 2000 BCE by Gudea. Use of the same standard continued through the Neo-Babylonian Empire, Neo-Assyrian Empire, and Achaemenid Empire.
Length
Units of length are prefixed by the logogram DU () a convention of the archaic period counting system from which it was evolved. Basic length was used in architecture and field division.
Distance units were geodectic as distinguished from non-geodectic basic length units. Sumerian geodesy divided latitude into seven zones between equator and pole.
Area
The GAN2 system G counting system evolved into area measurements. A special unit measuring brick quantity by area was called the brick-garden (Cuneiform: SIG.SAR ; Sumerian: šeg12-sar; Akkadian: libittu-mūšaru) which held 720 bricks.
Capacity or volume
Capacity was measured by either the ŠE system Š for dry capacity or the ŠE system Š* for wet capacity.
A sila was about 1 liter.
Mass or weight
Mass was measured by the EN system E
Values below are an average of weight artifacts from Ur and Nippur. The ± value represents 1 standard deviation. All values have been rounded to second digit of the standard deviation.
Time
In the Archaic System time notation was written in the U4 System U. Multiple lunisolar calendars existed; however the civil calendar from the holy city of Nippur (Ur III period) was adopted by Babylon as their civil calendar. The calendar of Nippur dates to 3500 BCE and was itself based on older astronomical knowledge of an uncertain origin. The main astronomical cycles used to construct the calendar were the month, year, and day.
Relationship to other metrologies
The Classical Mesopotamian system formed the basis for Elamite, Hebrew, Urartian, Hurrian, Hittite, Ugaritic, Phoenician, Babylonian, Assyrian, Persian, Arabic, and Islamic metrologies. The Classical Mesopotamian System also has a proportional relationship, by virtue of standardized commerce, to Bronze Age Harappan and Egyptian metrologies.
See also
Assyrian lion weights
Babylonian mathematics
Historical weights and measures
Weights and measures
References
Citations
Bibliography
Further reading
External links
An online calculator
Sumerian art and architecture
Babylonia
Sumer
Measurement
Mesopotamian
Mesopotamian
Mesopotamian
Mesopotamian | Ancient Mesopotamian units of measurement | Mathematics | 1,363 |
10,942,957 | https://en.wikipedia.org/wiki/Motexafin%20gadolinium | Motexafin gadolinium (proposed tradename Xcytrin) is an inhibitor of thioredoxin reductase and ribonucleotide reductase. It has been proposed as a possible chemotherapeutic agent in the treatment of brain metastases.
History
On May 9, 2006, a New Drug Application was submitted to the United States Food and Drug Administration (FDA) by Pharmacyclics, Inc.
In December 2007, the FDA issued a not approvable letter for motexafin gadolinium.
References
Organogadolinium compounds | Motexafin gadolinium | Chemistry,Biology | 124 |
1,335,938 | https://en.wikipedia.org/wiki/NexTView | NexTView was an electronic program guide for the analog domain, introduced in 1995 and based on Teletext Level 2.5 / Hi-Text.
It was used by TV programme listings for all of the major networks in Germany, Austria, France and Switzerland. The transmission protocol was based on teletext, however, using a compact binary format instead of preformatted text pages. The advantage compared to paper-based TV magazines was that the user had an immediate overview of the current and next programmes, and was able to search through the programme database, filtering results by categories.
The nxtvepg software enabled nexTView to be viewed using a personal computer.
Some TV manufacturers that implemented this solution were: Grundig, Loewe, Metz, Philips, Sony, Thomson, and Quelle Universum.
From 1997 to October 2013, NexTView was broadcast on Swiss Television channels and on French-language channels whose teletext services were managed from Swiss Television (SwissText) (TV5, M6, Canal+).
See also
Guide Plus
AV.link
References
Television technology
Multimedia
Teletext | NexTView | Technology | 227 |
43,385,931 | https://en.wikipedia.org/wiki/Data%20exploration | Data exploration is an approach similar to initial data analysis, whereby a data analyst uses visual exploration to understand what is in a dataset and the characteristics of the data, rather than through traditional data management systems. These characteristics can include size or amount of data, completeness of the data, correctness of the data, possible relationships amongst data elements or files/tables in the data.
Data exploration is typically conducted using a combination of automated and manual activities. Automated activities can include data profiling or data visualization or tabular reports to give the analyst an initial view into the data and an understanding of key characteristics.
This is often followed by manual drill-down or filtering of the data to identify anomalies or patterns identified through the automated actions. Data exploration can also require manual scripting and queries into the data (e.g. using languages such as SQL or R) or using spreadsheets or similar tools to view the raw data.
All of these activities are aimed at creating a mental model and understanding of the data in the mind of the analyst, and defining basic metadata (statistics, structure, relationships) for the data set that can be used in further analysis.
Once this initial understanding of the data is had, the data can be pruned or refined by removing unusable parts of the data (data cleansing), correcting poorly formatted elements and defining relevant relationships across datasets. This process is also known as determining data quality.
Data exploration can also refer to the ad hoc querying or visualization of data to identify potential relationships or insights that may be hidden in the data and does not require to formulate assumptions beforehand.
Traditionally, this had been a key area of focus for statisticians, with John Tukey being a key evangelist in the field. Today, data exploration is more widespread and is the focus of data analysts and data scientists; the latter being a relatively new role within enterprises and larger organizations.
Interactive Data Exploration
This area of data exploration has become an area of interest in the field of machine learning. This is a relatively new field and is still evolving. As its most basic level, a machine-learning algorithm can be fed a data set and can be used to identify whether a hypothesis is true based on the dataset. Common machine learning algorithms can focus on identifying specific patterns in the data. Many common patterns include regression and classification or clustering, but there are many possible patterns and algorithms that can be applied to data via machine learning.
By employing machine learning, it is possible to find patterns or relationships in the data that would be difficult or impossible to find via manual inspection, trial and error or traditional exploration techniques.
Software
Trifacta – a data preparation and analysis platform
Paxata – self-service data preparation software
Alteryx – data blending and advanced data analytics software
Microsoft Power BI - interactive visualization and data analysis tool
OpenRefine - a standalone open source desktop application for data clean-up and data transformation
Tableau software – interactive data visualization software
See also
Exploratory data analysis
Machine learning
Data profiling
Data visualization
References
Machine learning
Data analysis
Data management
Data quality | Data exploration | Technology,Engineering | 632 |
64,038,257 | https://en.wikipedia.org/wiki/Eustachius%20Roche | Eustachius Roche (floruit 1570-1600) was a Flemish mining entrepreneur in Scotland.
Roche was granted a monopoly to mine metals in Scotland, and work salt on the shore near Edinburgh, but his contract was terminated in 1592.
His surname was sometimes written "Roghe", or Rogghe", or "Roogh". He lived in Leith.
He had a contract for lead mining in 1580. In August 1583 James VI granted Eustachius Roche a contract with monopoly rights to mine for gold, silver, copper, and lead in Scotland. He was described as a "mediciner", a physician. There were other miners at this period including George Douglas of Parkhead and Thomas Foulis. A note made in September 1584 about his work at Wanlockhead reports that Roche had worked lead and copper, and searched for copper on Langcleuch burn, but not the gold at the old mines. One of his men was called John Gibson.
He seems also to have worked for Francis Walsingham, and wrote to him in April 1583 about an opportunity to serve England involving the French ambassador which he had taken. James VI gave a mineral entrepreneur, evidently Roche, a letter of introduction to Walsingham in January 1584. He was travelling abroad to find expert workmen.
On 25 September 1588 Eustachius wrote from Edinburgh to a colleague Geoffrey le Broman. He discussed their alchemical practices. He had also been making salt from sea water, and claimed to have a new method that would undercut the price of French salt. He had made a contract with James VI that would make him rich, and Robert Sidney, who had recently been English ambassador in Edinburgh, had begun to discuss a similar privilege for him in England. Sidney left Edinburgh sooner than planned because of the death of his uncle, the Earl of Leicester. Roche thought Geoffrey could forward his schemes by reminding Sidney, preferably by approaching an acquaintance, Stephen Lesieur, Sidney's secretary. Geoffrey might also speak to Francis Walsingham. He enclosed a sample of salt and some Scottish flax that might interest a Master Martin. Eustachius sent a copy of his salt contract, to work salt pans at Newhaven on the west side of Leith, as a model.
Roche had these privileges for his trade secret, "the form of his furnaces and making of his great salt, which he will he not be content be communicated to others". In April 1588 the Privy Council, impressed with his estimates to improve revenue, made an act that Roche's heirs would inherit his 10% share. The council also declared it would seek justice for the murder of his workman Nicholas Wanraust or Van Raust.
On 27 December 1588 Edinburgh council allowed Roche the same lease or "tack" of lands at Newhaven, as the Englishmen had before, meaning the works previously set to Cornelius de Vos and his partners. The works were at the shore of the Wester Links of Leith between Wardie Brow and St Nicolas Chapel. In July 1590 he was asked to pay three years arrears of rent for the Newhaven holding. He gave up his lease on 12 May 1592.
In 1592 David Lindsay of Edzell complained to the Privy Council about Roche and his contract for metals. Lindsay had discovered copper on his lands of Glen Esk and Edzell. But Roche had a monopoly on mining in Scotland, so Lindsay offered to form a partnership. He wanted the Privy Council to summon Roche and make him form a partnership or allow Lindsay to manage his own mines. Accordingly, Roche and Lindsay formed a partnership, and Roche was to pay his share of Lindsay's costs to date. This was a manoeuvre to wrongfoot Roche.
Soon after, in June 1592, the Parliament of Scotland created a new office, the Master of Metals to be in charge of mines and refining. John Lindsay of Menmuir, the brother of David Lindsay, was appointed. In order to ensure Roche resigned his rights, information damaging his reputation was collected from the Dutch Republic and Flanders by the means of the diplomat Adrian van Damman, the Conservator of Scottish Privileges at Veere, and a Scottish merchant in Antwerp, Jacques Barron, and it was said he was of "evil fame." The murder of one of his workmen, Nicholas van Raust, at the lead mine by a man called Gibson was deemed irrelevant to mining issues.
Robert Jousie, whose business partner Thomas Foulis had a copper mine, wrote to the Conservator of Privileges, Robert Dennistoun, about an old legal case concerning Roche, who confirmed "It imports no small dishonour and interest to his Majesty and the country so long to suffer an infamous person to have charge of the mines."
Archibald Napier of Merchiston Castle responded to the act appointing Lindsay and advised on the "reduction", the legal challenge, to Roche's contract. While interested parties were submitting their views to the Privy Council, Marion Douglas, the wife of George Douglas of Parkhead, was trying to manage their lead and silver mines in August 1592. She wrote to Menmuir about the uncertain status of their contract in the new legislative framework. She had to put the workmen to other tasks, or lay them off.
Eustachius Roche's mining rights were removed, and he may have left Scotland. His son Frederick was baptised in Edinburgh on 2 August 1597.
In 1599 his monopolies and patents for improved kilns and stoves, chimneys and furnaces were ratified by the Parliament of Scotland. Roche petitioned the king to supply him with pans as per the contract. The king awarded a share of the potential income to Colonel William Stewart.
References
Gold mines in Scotland
Mining engineers
Flemish metallurgists
16th-century alchemists | Eustachius Roche | Chemistry,Engineering | 1,201 |
47,187,269 | https://en.wikipedia.org/wiki/4-Mercaptophenylacetic%20acid | MPAA (4-Mercaptophenylacetic acid) is a redox buffer that increases the folding rate of disulfide-containing proteins.
MPAA is also used in native chemical ligation as a thiol catalyst.
Acetic acids
Aromatic compounds
Thiols | 4-Mercaptophenylacetic acid | Chemistry | 58 |
5,322,320 | https://en.wikipedia.org/wiki/Axiom%20of%20global%20choice | In mathematics, specifically in class theories, the axiom of global choice is a stronger variant of the axiom of choice that applies to proper classes of sets as well as sets of sets. Informally it states that one can simultaneously choose an element from every non-empty set.
Statement
The axiom of global choice states that there is a global choice function τ, meaning a function such that for every non-empty set z, τ(z) is an element of z.
The axiom of global choice cannot be stated directly in the language of Zermelo–Fraenkel set theory (ZF) with the axiom of choice (AC), known as ZFC, as the choice function τ is a proper class and in ZFC one cannot quantify over classes. It can be stated by adding a new function symbol τ to the language of ZFC, with the property that τ is a global choice function. This is a conservative extension of ZFC: every provable statement of this extended theory that can be stated in the language of ZFC is already provable in ZFC . Alternatively, Gödel showed that given the axiom of constructibility one can write down an explicit (though somewhat complicated) choice function τ in the language of ZFC, so in some sense the axiom of constructibility implies global choice (in fact, [ZFC proves that] in the language extended by the unary function symbol τ, the axiom of constructibility implies that if τ is said explicitly definable function, then this τ is a global choice function. And then global choice morally holds, with τ as a witness).
In the language of von Neumann–Bernays–Gödel set theory (NBG) and Morse–Kelley set theory, the axiom of global choice can be stated directly , and is equivalent to various other statements:
Every class of nonempty sets has a choice function.
V \ {∅} has a choice function (where V is the class of all sets).
There is a well-ordering of V.
There is a bijection between V and the class of all ordinal numbers.
In von Neumann–Bernays–Gödel set theory, global choice does not add any consequence about sets (not proper classes) beyond what could have been deduced from the ordinary axiom of choice.
Global choice is a consequence of the axiom of limitation of size.
References
Jech, Thomas, 2003. Set Theory: The Third Millennium Edition, Revised and Expanded. Springer. .
John L. Kelley; General Topology;
Axioms of set theory
Axiom of choice | Axiom of global choice | Mathematics | 532 |
1,073,121 | https://en.wikipedia.org/wiki/Mott%20MacDonald | The Mott MacDonald Group is a management, engineering and development consultancy headquartered in the United Kingdom. It employs over 18,000 staff in 150 countries. Mott MacDonald is one of the largest employee-owned companies in the world.
History
Mott MacDonald was formed in 1989 through the merger of Mott, Hay and Anderson and Sir M MacDonald & Partners. Mott, Hay and Anderson was a transportation engineering consultancy responsible for projects such as the London Underground while Sir M MacDonald & Partners was a water engineering consultancy with projects that included the Aswan Dam. The merger made Mott MacDonald one of the first international engineering, management, and development consultancies.
Mott, Hay & Anderson
Mott, Hay and Anderson was founded as a private partnership between Basil Mott and David Hay in 1902, with the original firm name of Mott & Hay. Prior to forming the original partnership, Mott and Hay had spent time building London tube railways and Hay had worked on the Blackwall Tunnel. Both engineers had worked together since 1888 on the City & South London Railway under Sir Benjamin Baker and James Henry Greathead. Early projects included the reconstruction and extension of the City and South London Railway (C&SLR), the building and extension of the Central London Railway, the construction of lifts beneath St Mary Woolnoth church at Bank tube station, the underpinning of Clifford's Tower, the reconstruction of Southwark Bridge and the widening of Blackfriars Bridge. Mott and Hay employed a young engineer called David Anderson as resident engineer for the latter project.
The firm also advised on proposals for underground railways in Sydney, Africa, and Russia. David Anderson was made a partner in 1920 after returning from army service. The firm was thereafter known as Mott, Hay and Anderson. During the 1920s, it designed the rolling bridge over the River Dee at Queensferry, the Tyne Bridge in Newcastle and the Trent Bridge in Nottingham. It also designed the enlargement of the City & South London Railway tunnels and their extension past Camden Town and Clapham South to form the Northern line of the London Underground.
Both founding partners died in 1938, at which time most of the construction projects stopped. During the 1940s after World War II, it began expanding and working on additional projects, some of which including repairing of roads and bridges damaged or destroyed during the war, and, later, included the Victoria line of the London Underground and Australia's Melbourne Underground Rail Loop. The firm continued in these fields until the merger with Sir M MacDonald & Partners in 1989, at which time it was also working on the Channel Tunnel between the United Kingdom and France beneath the English Channel.
Sir M MacDonald & Partners
Sir M MacDonald & Partners was named after Murdoch Macdonald, a British civil engineer and later politician. The company formed out of affairs relating directly to British infrastructure development in Egypt between 1890 and 1930, in particular MacDonald's involvement with Aswan Low Dam, starting in 1898. MacDonald was involved in the original construction of the Aswan Dam and later became an advisor to the Egyptian Ministry of Public Works after the dam was completed in 1902. He became closely associated with the development and first heightening of the Aswan Low Dam for the development of hydroelectricity.
MacDonald retired from his service with the Egyptian government in 1921 and returned to Britain where he began a partnership with Archibald MacCorquodale. In 1927, the two were later joined by PH East (also an engineer in the Egyptian government from 1907 to 1926) and Oswald Longstaff Prowde, at which time the name of the company was changed to Sir M MacDonald & Partners. One of the first major projects of the partnership included the second heightening of the Aswan Low Dam, which continued from 1929 through design and construction stages until 1933. The firm continued on projects through its merger with Mott, Hay and Anderson in 1989.
Post-merger
Mott MacDonald began to expand after the 1989 merger. Early acquisitions included the consultancies of Husband & Company as well as James Williamson & Partners. These acquisitions brought Mott MacDonald's total staffing to 3,300. Its 1994 acquisition of Ewbank Preece expanded its reach into the power and telecommunication fields, with its 2000 purchase of Cambridge Education Associates expanding its education consultancy. Additional early acquisitions included India-based firm Dalal Consultants in 2001, cost consultants Franklin + Andrews in 2002 and health practice HLSP in 2003. In 2007, Mott MacDonald bought Dutch firm Euroconsult BMB who specialized in international development and natural resource management.
2008 marked the first year that Mott MacDonald earned more internationally than it did in the United Kingdom, earning it recognition by New Civil Engineer as the International Consultant of the Year. Its top two international projects for that year were the Delhi Metro in India and Macau City of Dreams in China. The same year, the firm had 7,021 staff assigned to overseas projects, with 6,669 working overseas.
Mott MacDonald purchased Fulcrum Consulting in 2009 as a way of expanding its sustainable energy consultancy in the building sector. Fulcrum was a building services engineer consultancy and a founding member of the UK Green Building Council, specializing in green and eco-friendly engineering and design. Fulcrum was responsible for projects such as the Darwin Centre and considered a pioneer of low-energy building techniques. MacDonald also expanded to open principal offices in Turkey, Kazakhstan, Albania, and Serbia while opening smaller offices in throughout Africa. It also purchased Merz & McLellan, a South African electrical engineering consultancy. 2009 also marked the opening of Mbombela Stadium, a stadium in South Africa for which Mott MacDonald designed the roof. In 2010, the firm added South African healthcare and development specialist HDA, and Australian engineering consultancy Hughes Trueman to its portfolio. In 2011, Mott MacDonald purchased Australian firm Mortimer Project Management and opened an office in Auckland, New Zealand.
Mott MacDonald continued to expand its international presence in April 2013 with the purchase of Habtec Engenharia Ambiental, a Brazil-based environmental consultancy with 80 people. Later the same month, it purchased PD Naidoo & Associates, a consultancy based in South Africa with 550 people. The acquisitions added to the company's previous purchases of Canadian consultancy Engineering Northwest, oil and gas firm Procyon, and the oil and gas operations of Mouchel.
In 2014, Mott MacDonald acquired AWT, a specialist water technology and consulting company based in New Zealand and Australia.
During 2014, Mott MacDonald acquired its UK water industry design and build joint venture partner Bentley Holdings Ltd (including its subsidiary company JN Bentley Ltd). The move was a natural progression in the highly successful 15 year partnership between the companies through the joint venture Mott MacDonald Bentley.
In 2015, Mott MacDonald and Hatch have announced that the Hatch Mott MacDonald (HMM) joint venture will be separated into two distinct businesses. HMM’s Canada business will become part of Hatch while HMM’s US business will become part of Mott MacDonald. HMM’s pipelines business, which operates in both Canada and the US, will also join Mott MacDonald.
Projects
Mott MacDonald has worked on many notable projects. It was the design engineer for Heathrow Terminal 5 sub-structures and foundations, as well as providing rail assurance services, tunnelling advice and project and program management. The project began in 2002, with construction being completed in 2008.
Mott MacDonald was the engineer and worked with Denton Corker Marshall on the design of the Manchester Civil Justice Centre which was completed in 2007. The Centre was the largest court complex in the United Kingdom built in a century and has won 26 awards for its design, including the Major Project of the Year Award in 2008 from Building.com. The Centre was designed and constructed to have minimal impact on the environment and included a narrow form, acoustic privacy, and natural ventilation. It was also featured in the book Microgeneration: Low Energy Strategies for Larger Buildings for its sustainability features.
In 2012, Mott MacDonald was chosen as the concept designer for engineering the New Mosaic Stadium.
Mott MacDonald was chosen to be part of the design-build team for a $41 million bridge rehabilitation project announced by New York Governor Andrew Cuomo in January 2014. The project is scheduled to repair bridges in Niagara County in the western part of New York.
The $125 million contract for engineering the single bore tunnel segment of the Silicon Valley BART extension was awarded to a joint venture bid placed by Mott MacDonald and San Francisco based PGH Wong Engineering in January 2019.
Since 1998, Mott MacDonald has been providing waste water management for Union Pacific. In January 2018, a Mott MacDonald employee distracted by a cell phone call left a tank unattended for an hour while working at the railroad's Albina Yard in Portland, Oregon, United States. The tank overflowed and released several thousands gallons of oil into the environment according to US attorneys. 1,800 gallons of the released oil was estimated to have been lost into the Willamette River. The former employee Robert LaRue Webb II was convicted with violating the Clean Water Act in October 2019 and was sentenced to a probation and a fine for negligently causing the oil release. The clean up and emergency response cost the railroad over $500,000. United States Coast Guard, EPA and Oregon Department of Environmental Quality assisted with the clean up.
Further reading
Newman Neame Ltd. (1965), Mott, Hay & Anderson, Consulting Civil Engineers
Mott MacDonald (2002), One hundred years of transportation
References
External links
Cambridge Education
Mott MacDonald Bentley
Construction and civil engineering companies established in 1989
Construction and civil engineering companies of the United Kingdom
Consulting firms established in 1989
Design companies established in 1989
Employee-owned companies of the United Kingdom
Engineering consulting firms of the United Kingdom
International engineering consulting firms
Technology companies established in 1989
1989 establishments in England | Mott MacDonald | Engineering | 1,994 |
17,727,732 | https://en.wikipedia.org/wiki/Annular%20velocity | Annular velocity is the speed of the drilling fluid's movement in a column called an annulus in oil wells. It is commonly measured in feet per minute (ft/min) or meters per minute (m/min). Annular velocity is often abbreviated as AV, though this is not exclusively so, as AV also refers to apparent viscosity which is calculated from rheometer readings from tests that the mud engineer performs.
Scope
For this article, annular velocity is described, as used in drilling fluid applications in the oil exploration industry. There may be other applications in other fields of study such as fluid mechanics (the study of the movement of fluid) or fluid dynamics (the study of the flow of fluid).
Determination
The annular velocity can be calculated using one of the following formulas.
Or
Where:
AV = annular velocity in Ft/min (feet per minute)
PObpm = pump output in bpm (barrels per minute) 1 barrel = 42 gallons
POgpm = pump output in gpm (gallons per minute) 1 gallon = 0.0238095238 barrels
ID2 = inside diameter of the wellbore or casing, squared
OD2 = outside diameter of the drill pipe or tubing, squared
1029.4 = A conversion factor constant used to calculate the volume between the outside of a tube within the inside of another tube, using barrels.
24.5 = A conversion factor constant used to calculate the volume between the outside of a tube within the inside of another tube, using gallons.
Pump Output = Refers to the measurement of the quantity of a fluid (to put that fluid in motion).
Application
The annular velocity is one of two major variables in the process of cleaning
solids (drill cuttings) from the wellbore. By maintaining the annular velocity at certain rates (speeds) in conjunction with the rheological properties of the drilling fluid, the wellbore is kept clean of the drill cuttings to prevent them from settling back down to the bottom and causing drilling problems.
The other major variable is the rheology of the drilling fluid. Rheology is sometimes thought of as viscosity to the uninitiated, though improperly. Viscosity (sometimes thought of as its thickness) is a very basic measurement of the fluids resistance to change in movement or flow. The viscosity of a fluid can be measured with a Marsh Funnel. Rheology is the study of viscosity and requires more precise and complicated procedures and equipment for its determination. For drilling fluid applications a rheometer is used.
See also
Petroleum Engineering
Drilling rig
Oilfield
Oil well
List of acronyms in oil and gas exploration and production
List of oilfield service companies
List of oil fields
Natural gas field
References
Fluid dynamics
Drilling fluid | Annular velocity | Chemistry,Engineering | 568 |
16,295 | https://en.wikipedia.org/wiki/Josiah%20Wedgwood | Josiah Wedgwood (12 July 1730 – 3 January 1795) was an English potter, entrepreneur and abolitionist. Founding the Wedgwood company in 1759, he developed improved pottery bodies by systematic experimentation, and was the leader in the industrialisation of the manufacture of European pottery.
The renewed classical enthusiasms of the late 1760s and early 1770s were of major importance to his sales promotion. His expensive goods were in much demand from the upper classes, while he used emulation effects to market cheaper sets to the rest of society. Every new invention that Wedgwood produced – green glaze, creamware, black basalt, and jasperware – was quickly copied. Having once achieved efficiency in production, he obtained efficiencies in sales and distribution. His showrooms in London gave the public the chance to see his complete range of tableware.
Wedgwood's company never made porcelain during his lifetime, but specialised in fine earthenwares and stonewares that had many of the same qualities, but were considerably cheaper. He made great efforts to keep the designs of his wares in tune with current fashion. He was an early adopter of transfer printing which gave similar effects to hand-painting for a far lower cost. Meeting the demands of the consumer revolution that helped drive the Industrial Revolution in Britain, Wedgwood is credited as a pioneer of modern marketing. He pioneered direct mail, money-back guarantees, self-service, free delivery, buy one get one free, and illustrated catalogues.
A prominent abolitionist fighting slavery, Wedgwood is remembered too for his Am I Not a Man And a Brother? anti-slavery medallion, which had been commissioned by Joseph Hooper, a founder of the Society for Effecting the Abolition of the Slave Trade. The medallion used the design from that society.
Wedgwood was a member of the Darwin–Wedgwood family, and he was the grandfather of Charles and Emma Darwin.
Early life
There were several related Wedgwood families in the village of Burslem, which around 1650 was the main centre of Staffordshire Potteries. Each pot-works had one bottle kiln. Thomas Wedgwood set up the Churchyard Works, near St John's parish church. In 1679 the business went to his son of the same name, master potter and churchwarden who bought a family pew, whose son Thomas, born in 1685, married Mary Stringer around 1710. She was the daughter of Josiah Stringer, a dissenting minister whose church had been outlawed by the Corporation Act, but preached occasionally. The young Thomas and Mary moved to a small pot-works producing moulded ware, then after his father died in 1716 they moved back to the Churchyard Works. Their first son, Thomas, was born in 1716, Catherine was born in 1726, and Josiah was their thirteenth and last child.
The children were baptised in the parish church; Josiah was baptised on 12 July 1730, probably his date of birth. Though her husband continued to occupy the pew, Mary brought them up with the values taught by her father, who held that "knowledge based on reason, experience, and experiment was preferable to dogma." Josiah went with the others to dame school then, around 1737 when able to walk to and from Newcastle-under-Lyme about distant, he went with them to the school there of Mr and Mrs Blunt, who were reputably Puritans.
After his father died in June 1739, Josiah finished school then, at about the usual age, began an informal apprenticeship and learnt to "throw" pots on the potter's wheel. When nearly twelve, he suffered a severe bout of smallpox which affected his right knee, but recovered sufficiently to get a formal indenture on 11 November 1744, serving as an apprentice potter under his eldest brother Thomas, who had taken over the Churchyard Works. Josiah resumed potter's wheel work for a year or two until his knee pains returned, causing him to turn to moulded ware and small ornaments. His brother thought his ideas of improvements unnecessary, and turned down his proposed partnership, so in 1751 or 1752 Josiah worked as a partner and manager in a pot-works near Stoke.
Several potters locally used practical chemistry to innovate, and Wedgwood very soon went into partnership with Thomas Whieldon, who made high value small items such as snuff boxes. After six months of research and preparation, Wedgwood developed an exceptionally brilliant green glaze, and there was immediate demand for products with this glaze. Like his partner, Wedgwood occasionally took samples to Birmingham wholesalers to get orders, making business contacts. Unfortunately a knee injury spread to general inflammation, forcing him to convalesce in his room for several months. He took this as an opportunity to extend his education, reading literature and science books. His studies were helped by repeated visits from Wiliam Willet, minister of Newcastle-under-Lyme Meeting House, who had married Wedgwood's sister Catherine in 1754; "a man of extensive learning and general acquirements". Josiah attended this English Presbyterian chapel, later known as Unitarian, and was a friend of Willet.
Around 1759, Wedgwood expanded his Burslem business, renting Ivy House Works and cottage from his distant cousins John and Thomas. They were often visited by their brother Richard Wedgwood, a wealthy Congleton cheesemonger, along with his daughter Sarah. She had been well educated, as was Unitarian practice, soon "Jos" wrote to his "loving Sally".
On a business trip in 1762, Wedgwood had another knee accident. After attention from a surgeon, he was accommodated by Thomas Bentley, who would become his close business associate. While recuperating, he met the chemist Joseph Priestley, who became a close friend, and discussed his dissenting theological ideas. In May Wedgwood began a long correspondence with Bentley, writing from Burslem, and moved into larger premises, the Brick House Works and dwelling.
Marriage and children
Wedgwood had wooed his distant cousin Sarah (1734–1815) since first meeting her, but her father Richard wanted to ensure his prospective son-in-law had sufficient means, and insisted on long negotiation by attorneys over the marriage settlement. Then, "Jos" and "Sally" were married on 25 January 1764 at Astbury parish church, near Congleton. They had eight children:
Susannah Wedgwood (3 January 1765 – 1817), known to the family as "Sukey", married Robert Darwin and became the mother of the English naturalist Charles Darwin. Charles married Emma Wedgwood, his cousin.
John Wedgwood (1766–1844), joined the business rather reluctantly, being mainly interested in horticulture
Richard Wedgwood (1767–1768) (died as a child)
During negotiations for the proposed Trent and Mersey Canal, Wedgwood met and befriended Erasmus Darwin (Robert's father), whose family long remembered as saying that Unitarianism was "a feather-bed to catch a falling Christian".After more problems with his knee, Wedgwood had his leg amputated on 28 May 1768.
Josiah Wedgwood II (1769–1843) (father of Emma Darwin, cousin and wife of Charles Darwin)
The Etruria Works built at the canal opened in June 1769, in July the family moved there. For several months they stayed in Little Etruria, a house built for Bentley's use, then they moved into the just competed Etruria Hall.
Thomas Wedgwood (1771–1805) (no children), best known as a pioneer photographer
Catherine Wedgwood (1774–1823) (no children)
Sarah Wedgwood (1776–1856) (no children, very active in the abolition movement and founding member of Birmingham Ladies Society for the Relief of Negro Slaves, the first anti-slavery society for women)
Mary Anne Wedgwood (1778–86) (died as a child)
As a Unitarian, aware of legal constraints on nonconformists getting education, Wedgwood supported dissenting academies such as Warrington Academy, where he gave lectures on chemistry, and was made a professor of metallurgy. The older children first went to school in 1772; the boys to Hindley, while Sukey went to a dame school in Lancashire along with his niece, the daughter of Mrs. Willet. In 1774 he sent his son John to the Bolton boarding school trun by the Unitarian minister Philip Holland, followed by young Josiah the next year, and Tom in 1779.
Career and work
Pottery
Wedgwood was keenly interested in the scientific advances of his day and it was this interest that underpinned his adoption of its approach and methods to revolutionise the quality of his pottery. His unique glazes began to distinguish his wares from anything else on the market.
By 1763, he was receiving orders from the highest-ranking people, including Queen Charlotte. Wedgwood convinced her to let him name the line of pottery she had purchased "Queen's Ware", and trumpeted the royal association in his paperwork and stationery. Anything Wedgwood made for the Queen was automatically exhibited before it was delivered. In 1764, he received his first order from abroad. Wedgwood marketed his Queen's Ware at affordable prices, everywhere in the world British trading ships sailed. In 1767 he wrote, "The demand for this sd. Creamcolour, Alias, Queen Ware, Alias, Ivory, still increases – It is amazing how rapidly the use of it has spread over the whole Globe."
He first opened a warehouse at Charles Street, Mayfair in London as early as 1765 and it soon became an integral part of his sales organization. In two years, his trade had outgrown his rooms in Grosvenor Square. In 1767, Wedgwood and Bentley drew up an agreement to divide decorative wares between them, the domestic wares being sold on Wedgwood's behalf. A special display room was built to beguile the fashionable company. Wedgwood's in fact had become one of the most fashionable meeting places in London. His workers had to work day and night to satisfy the demand, and the crowds of visitors showed no sign of abating. The proliferating decoration, the exuberant colours, and the universal gilding of rococo were banished, the splendours of baroque became distasteful; the intricacies of chinoiserie lost their favour. The demand was for purity, simplicity and antiquity. To encourage this outward spread of fashion and to speed it on its way Wedgwood set up warehouses and showrooms at Bath, Liverpool and Dublin in addition to his showrooms at Etruria and in Westminster. Great care was taken in timing the openings, and new goods were held back to increase their effect.
The most important of Wedgwood's early achievements in vase production was the perfection of the black stoneware body, which he called "basalt". This body could imitate the colour and shapes of Etruscan or Greek vases which were being excavated in Italy. In 1769, "vases was all the cry" in London; he opened a new factory called Etruria, north of Stoke. Wedgwood became what he wished to be: "Vase Maker General to the Universe". Around 1771, he started to experiment with Jasperware, but he did not advertise this new product for a couple of years.
Sir George Strickland, 6th Baronet, was asked for advice on getting models from Rome. Gilding was to prove unpopular, and around 1772, Wedgwood reduced the amount of "offensive gilding" in response to suggestions from Sir William Hamilton. When English society found the uncompromisingly naked figure of the classics "too warm" for their taste, and the ardor of the Greek gods too readily apparent, Wedgwood was quick to cloak their pagan immodesty – gowns for the girls and fig leaves for the gods were usually sufficient. Just as he felt that his flowerpots would sell more if they were called "Duchess of Devonshire flowerpots", his creamware more if called Queensware, so he longed for Brown, James Wyatt, and the brothers Adam to lead the architect in the use of his chimneypieces and for George Stubbs to lead the way in the use of Wedgwood plaques.
Wedgwood hoped to monopolise the aristocratic market and thus win for his wares a special social cachet that would filter to all classes of society. Wedgwood fully realised the value of such a lead and made the most of it by giving his pottery the name of its patron: Queensware, Royal Pattern, Russian pattern, Bedford, Oxford and Chetwynd vases for instance. Whether they owned the original or merely possessed a Wedgwood copy mattered little to Wedgwood's customers. In 1773 they published the first Ornamental Catalogue, an illustrated catalogue of shapes. A plaque, in Wedgwood's blue pottery style, marking the site of his London showrooms between 1774 and 1795 in Wedgwood Mews, is located at 12, Greek Street, London, W1.
In 1773, Empress Catherine the Great ordered the (Green) Frog Service from Wedgwood, consisting of 952 pieces and over a thousand original paintings, for the Kekerekeksinen Palace (palace on a frog swamp ), later known as Chesme Palace. Most of the painting was carried out in Wedgwood's decorating studio at Chelsea. Its display, Wedgwood thought, 'would bring an number of People of Fashion into our Rooms. For over a month the fashionable world thronged the rooms and blocked the streets with their carriages. (Catharine paid £2,700. It can still be seen in the Hermitage Museum.) Strictly uneconomical in themselves, these productions offered huge advertising value.
Later years
As a leading industrialist, Wedgwood was a major backer of the Trent and Mersey Canal dug between the River Trent and River Mersey, during which time he became friends with Erasmus Darwin. Later that decade, his burgeoning business caused him to move from the smaller Ivy Works to the newly built Etruria Works, which would run for 180 years. The factory was named after the Etruria district of Italy, where black porcelain dating to Etruscan times was being excavated. Wedgwood found this porcelain inspiring, and his first major commercial success was its duplication with what he called "Black Basalt". He combined experiments in his art and in the technique of mass production with an interest in improved roads, canals, schools, and living conditions. At Etruria, he even built a village for his workers. The motto, Sic fortis Etruria crevit ("Thus Etruria grew strong"), was inscribed over the main entrance to the works.
Not long after the new works opened, continuing trouble with his smallpox-afflicted knee made necessary the amputation of his right leg. In 1780, his long-time business partner Thomas Bentley died, and Wedgwood turned to Darwin for help in running the business. As a result of the close association that grew up between the Wedgwood and Darwin families, Josiah's eldest daughter would later marry Erasmus' son.
To clinch his position as leader of the new fashion, he sought out the famous Barberini vase as the final test of his technical skill. Wedgwood's obsession was to duplicate the Portland Vase, a blue-and-white glass vase dating to the first century BC. He worked on the project for three years, eventually producing what he considered a satisfactory copy in 1789.
In 1784, Wedgwood was exporting nearly 80% of his total produce. By 1790, he had sold his wares in every city in Europe. To give his customers a greater feeling of the rarity of his goods, he strictly limited the number of jaspers on display in his rooms at any given time, a sales technique detailed by Cambridge professor Neil McKendrick in "Josiah Wedgwood: An Eighteenth-Century Entrepreneur in Salesmanship and Marketing Techniques".
He was elected to the Royal Society in 1783 for the development of the pyrometric device (a type of pyrometer) working on the principle of clay contraction (see Wedgwood scale for details) to measure the high temperatures which are reached in kilns during the firing of ceramics.
He was an active member of the Lunar Society of Birmingham, often held at Erasmus Darwin House, and is remembered on the Moonstones in Birmingham.
Death
Leaving his company and his fortune to his children, Wedgwood died at home, probably of cancer of the jaw, in 1795. He was buried three days later in the parish church of Stoke-upon-Trent. Seven years later a marble memorial tablet commissioned by his sons was installed there.
Legacy and influence
One of the wealthiest entrepreneurs of the 18th century, Wedgwood created goods to meet the demands of the consumer revolution and growth in prosperity that helped drive the Industrial Revolution in Britain. He is credited as a pioneer of modern marketing, specifically direct mail, money-back guarantees, travelling salesmen, carrying pattern boxes for display, self-service, free delivery, buy one get one free, and illustrated catalogues. He is the subject of Brian Dolan's 2004 book, Wedgwood: The First Tycoon, in which Dolan explains how he revolutionised the business model with innovations that have continued into the present.
For devising a number of sales methods, historian Judith Flanders in The New York Times called him "among the greatest and most innovative retailers the world has ever seen". He is also noted as an early adopter/founder of managerial accounting principles by Anthony Hopwood, professor of accounting and financial management at the London School of Economics, in "The Archaeology of Accounting Systems". The V&A historian Tristram Hunt called Wedgwood a "difficult, brilliant, creative entrepreneur whose personal drive and extraordinary gifts changed the way we work and live." The Adam Smith Institute states, "Steve Jobs and Elon Musk are the spiritual heirs of Josiah Wedgwood, developing and promoting the new products and processes that will enrich our world with new opportunities".
He was a friend, and commercial rival, of the potter John Turner the elder; their works have sometimes been misattributed. For the further comfort of his foreign buyers he employed French-, German-, Italian- and Dutch-speaking clerks and answered their letters in their native tongue.
Wedgwood belonged to the fifth generation of a family of potters whose traditional occupation continued through another five generations. Wedgwood's company is still a famous name in pottery (as part of the Fiskars group), and "Wedgwood China" is sometimes used as a term for his Jasperware, the coloured pottery with applied relief decoration (usually white). As early as 1774, Wedgwood began preserving samples of all the company's works for posterity, with the collection later put into the Wedgwood Museum. In 2009, the museum won a UK Art Fund Prize for Museums and Art Galleries (Museum of the Year) for its displays of Wedgwood pottery, skills, designs and artefacts. In 2011, the archive of the museum was inscribed in UNESCO's UK Memory of the World Register.
Abolitionism
Wedgwood was a prominent slavery abolitionist. His friendship with Thomas Clarkson – abolitionist campaigner and the first historian of the British abolition movement – aroused his interest in slavery
[The above seems to be a closed arguement and unlikely to be true. Jospeh Hooper and Erasmus Darwin knew each other well, via the Medical Society of London, before Clarkson and Wedgwood became involved in the abolition movement. John Fothergill was their mentor as young Doctors. Darwin must have introduced Wedgwood to Hooper, and through Hooper, Wedgwood and Clarkson would have become known to one another].
Wedgwood mass-produced cameos depicting the seal for the Society for Effecting the Abolition of the Slave Trade and had them widely distributed, which thereby became a popular and celebrated image. The Wedgwood anti-slavery medallion was, according to the BBC, "the most famous image of a black person in all of 18th-century art". The actual design of the cameo was probably done by either William Hackwood or Henry Webber who were modellers at his factory.
From 1787 until his death in 1795, Wedgwood actively participated in the abolition-of-slavery cause. His anti-slavery medallion, which had been commissioned by Joseph Hooper, a founder of the Society for Effecting the Abolition of the Slave Trade, brought public attention to abolitionism. Wedgwood reproduced the design in a cameo with the black figure against a white background and donated hundreds to the society for distribution. Thomas Clarkson wrote: "ladies wore them in bracelets, and others had them fitted up in an ornamental manner as pins for their hair. At length the taste for wearing them became general, and thus fashion, which usually confines itself to worthless things, was seen for once in the honourable office of promoting the cause of justice, humanity and freedom".
The design on the medallion became popular and was used elsewhere: large-scale copies were painted to hang on walls and it was used on clay tobacco pipes.
Other
Erasmus Darwin House, Erasmus Darwin Museum house and gardens
A locomotive named "Josiah Wedgwood" ran on the Cheddleton Railway Centre in 1977. It returned in May 2016 following ten years away.
Commemorating the landing of the First Fleet at Sydney Cove in January 1788, Wedgwood made the Sydney Cove Medallion, using a sample of clay from the cove from Sir Joseph Banks, who had himself received it from Governor Arthur Phillip. Wedgwood made the commemorative medallion showing an allegorical group described as, "Hope encouraging Art and Labour, under the influence of Peace, to pursue the employments necessary to give security and happiness to an infant settlement".
Notes
References
McKendrick, Neil. "Josiah Wedgwood and the Commercialization of the Potteries", in: McKendrick, Neil; Brewer, John & Plumb, J.H. (1982), The Birth of a Consumer Society: The commercialization of Eighteenth-century England
Further reading
Hunt, Tristram. The Radical Potter: Josiah Wedgwood and the Transformation of Britain (2021)
Burton, Anthony. Josiah Wedgwood: A New Biography (2020)
Koehn, Nancy F. Brand New : How Entrepreneurs Earned Consumers' Trust from Wedgwood to Dell (2001) pp. 11–42.
Langton, John. "The ecological theory of bureaucracy: The case of Josiah Wedgwood and the British pottery industry." Administrative Science Quarterly (1984): 330–354.
McKendrick, Neil. "Josiah Wedgwood and Factory Discipline." Historical Journal 4.1 (1961): 30–55. online
McKendrick, Neil. "Josiah Wedgwood and cost accounting in the Industrial Revolution." Economic History Review 23.1 (1970): 45–67. online
McKendrick, Neil. "Josiah Wedgwood: an eighteenth-century entrepreneur in salesmanship and marketing techniques." Economic History Review 12.3 (1960): 408–433. online
Meteyard, Eliza. Life and Works of Wedgwood (2 vol 1865) vol 1 online; also vol 2 online
Reilly, Robin, Josiah Wedgwood 1730–1795 (1992), scholarly biography
Wedgwood, Julia, and Charles Harold Herford. The Personal Life of Josiah Wedgwood, the Potter (1915) online
Young, Hilary (ed.), The Genius of Wedgwood (exhibition catalogue), 1995, Victoria and Albert Museum,
External links
Wedgwood website
Vaizey, Marina, "Science into Art, Art into Science", The Tretyakov Gallery Magazine, No 2, 2016 (51) (good online summary)
Wedgwood collection at the Lady Lever Art Gallery
Wedgwood Museum
The Great Crash by Jenny Uglow, The Guardian, 7 February 2009
National Museum of Australia The Sydney Cove Medallion (Flash required for close-up viewing).
The Story of Wedgwood
Josiah Wedgwood Correspondence (transcripts), John Rylands Library, Manchester.
1730 births
1795 deaths
18th-century English people
Artists from Staffordshire
Burials in Staffordshire
Businesspeople from Staffordshire
Ceramics manufacturers of England
Darwin–Wedgwood family
English abolitionists
English amputees
English chief executives
English company founders
English potters
English Unitarians
Fellows of the Royal Society
Creators of temperature scales
Members of the Lunar Society of Birmingham
Neoclassical artists
People from Burslem
People of the Industrial Revolution
Staffordshire pottery
Wedgwood pottery
English inventors
English writers with disabilities
British artists with disabilities | Josiah Wedgwood | Physics | 5,086 |
74,508,938 | https://en.wikipedia.org/wiki/Ministers%27%20Wings | The Ministers' wings are outbuildings of the Palace of Versailles located in the Cour d'Honneur; the south wing now houses the Princes' bookshop and the ticket office, while the north wing is used to welcome groups of visitors.
History
Four pavilions were built for the Secretaries of State in 1671. Jules Hardouin-Mansart had the Ministers' wings built on the basis of these pavilions in 1679. The soberly ornamented Ministers' Wings, attached to the château, mark the end of the era of all-powerful ministers such as Fouquet, who defied the king with the construction of his château at Vaux-le-Vicomte. Each of the four secretaries of state occupied half a wing, and had access to all floors. The ground floor was devoted to work and reception areas, the second floor housed their apartments, their families were accommodated on the third floor, and the attic was used for clerks.
The two pavilions overlooking the Place d'Armes, at the end of the Ministers' wings, served under the Ancien Régime as guardhouses for the French and Swiss Guards, responsible for the castle's external protection. The French Guards occupied the end of the south wing, while the Swiss Guards occupied the north pavilion. Their officers had bedrooms on the upper floor of the guardhouse; they also had their own dining room and an "assembly room", where they could play tric-trac.
From 1958 onwards, the Ministers' wings housed the official residences and reception rooms for the presidents of the assemblies and the quaestors. The premises were returned to the Palace of Versailles in 2005 at the suggestion of National Assembly President Jean-Louis Debré.
The northern ministers' wing houses the lecturers' entrance and the school locker room, while the southern ministers' wing houses the princes' bookshop and the château's ticket office.
References
Palace of Versailles
Architecture by city | Ministers' Wings | Engineering | 395 |
51,693,525 | https://en.wikipedia.org/wiki/FEBS%20Open%20Bio | FEBS Open Bio is a monthly peer-reviewed open access scientific journal covering research and education in molecular and cellular life sciences. It was established in 2011 and is published by John Wiley & Sons on behalf of the Federation of European Biochemical Societies (FEBS). According to the journal, papers are not to be excluded on the basis of lack of perceived importance.
Articles originally submitted to other FEBS journals (FEBS Letters, The FEBS Journal, and Molecular Oncology) can be transferred to this journal with their original reviewer reports without the need to resubmit or reformat the manuscript.
Abstracting and indexing
The journal is abstracted and indexed in:
BIOSIS Previews
Embase
Scopus
Science Citation Index Expanded
According to the Journal Citation Reports, the journal has a 2015 impact factor of 2.101, ranking it 197th out of 289 journals in the category "Biochemistry & Molecular Biology".
References
External links
Molecular and cellular biology journals
Monthly journals
Academic journals established in 2011
Wiley (publisher) academic journals
English-language journals | FEBS Open Bio | Chemistry | 210 |
5,376,872 | https://en.wikipedia.org/wiki/Narratio%20Prima | De libris revolutionum Copernici narratio prima, usually referred to as Narratio Prima (), is an abstract of Nicolaus Copernicus' heliocentric theory, written by Georg Joachim Rheticus in 1540. It is an introduction to Copernicus's major work, De revolutionibus orbium coelestium, published in 1543, largely due to Rheticus's instigation. Narratio Prima is the first printed publication of Copernicus's theory.
History
Copernicus, born in 1473 and already well over 60 years old, had never published any astronomical work, as his only publication had been his translation of poems of Theophylact Simocatta, printed in 1509 by Johann Haller. At the same time, he had distributed his ideas among friends, with manuscripts called Commentariolus. In the 1530s, he was urged to publish by many, yet still hesitated when in 1539, Rheticus arrived in Frauenburg (Frombork) to become Copernicus' first and only pupil. Philipp Melanchthon had arranged for Rheticus to visit several astronomers and study with them.
In September 1539 Rheticus went to Danzig (Gdańsk) to visit the mayor who gave Rheticus some financial assistance to publish the Narratio Prima. This Narratio Prima, published by Franz Rhode in Danzig in 1540, is still considered to be the best introduction to Copernicus' De revolutionibus orbium coelestium. As the full title states, the Narratio was published as an open letter to Johannes Schöner of Nuremberg (Nürnberg). It was bundled together with the Encomium Prussiae which praised the spirit of humanism in Prussia.
During his two-year stay in Prussia, Rheticus published works of his own, and in cooperation with Copernicus, in 1542 a treatise on trigonometry which was a preview to the second book of De revolutionibus. Under strong pressure from Rheticus, and having seen the favorable first general reception of the Narratio Prima, Copernicus finally agreed to give the book to his close friend, bishop Tiedemann Giese, to be delivered to Nuremberg for printing by Johannes Petreius under Rheticus's supervision.
Later editions of Narratio Prima were printed in Basel, in 1541 by Robert Winter, and in 1566 by Henricus Petrus in connection with the second edition of De revolutionibus. In 1597 when Johannes Kepler's first book Mysterium Cosmographicum was prepared for publication in Tübingen, his advisor Michael Maestlin decided to include Rheticus' Narratio Prima following Kepler's text, as a supplementary explanation of heliocentric theory.
References
Bibliography
Rheticus: Narratio prima de libris revolutionum Copernici, Danzig 1540
Richard S. Westfall, Indiana University. Rheticus, George Joachim. "Catalog of the Scientific Community of the 16th and 17th Centuries," The Galileo Project.
Dennis Danielson (2006). The First Copernican: Georg Joachim Rheticus and the Rise of the Copernican Revolution. Walker & Company, New York.
Karl Heinz Burmeister: Georg Joachim Rhetikus 1514–1574. Bd. I–III. Guido Pressler Verlag, Wiesbaden 1967.
Stefan Deschauer: Die Arithmetik-Vorlesung des Georg Joachim Rheticus, Wittenberg 1536: eine kommentierte Edition der Handschrift X-278 (8) der Estnischen Akademischen Bibliothek; Augsburg: Rauner, 2003;
R. Hooykaas: G. J. Rheticus’ Treatise on holy scripture and the motion of the earth / with transl., annotations, commentary and additional chapters on Ramus-Rheticus and the development of the problem before 1650; Amsterdam: North-Holland, 1984
External links
Scienceworld article on Rheticus
Narratio Prima (1540) – scanned edition at Linda Hall Library
in English
Astronomy books
1540 books | Narratio Prima | Astronomy | 875 |
70,705,948 | https://en.wikipedia.org/wiki/Proacrodon | Proacrodon is a dubious genus of extinct mammal from South America. Its type species is Proacrodon transformatus. The only known specimen, a lower premolar or molar, is now lost, and its affinities are unknown.
In 1899, Santiago Roth named the new genus and species Proacrodon transformatus on the basis of a single tooth collected in Patagonia. The genus name comes from Greek πρό "before", άκρος "pointed", and όδών "tooth", and refers to the shape of the tooth, which rises higher in its anterior portion than its posterior portion. Roth compared the taxon to Megacrodon, which he named in the same paper, and to Hyrachyus. Florentino Ameghino synonymized Proacrodon with his own genus Trimerostephanus without seeing the specimen firsthand. In 1904, Palmer listed both Proacrodon and Trimerostephanos as members of Isotemnidae. In 1948 George Gaylord Simpson listed the taxon as a possible litoptern and concluded that the taxon was a nomen vanum, viewing Ameghino's proposal of synonymy with Trimerostephanos as possible but not reliable.
The locality where the tooth was collected is not known with certainty, but was probably in the Musters Formation.
References
Works cited
Litopterns
Nomina dubia
Fossil taxa described in 1899
Prehistoric placental genera | Proacrodon | Biology | 302 |
14,215,182 | https://en.wikipedia.org/wiki/D-lysine%205%2C6-aminomutase | In enzymology, D-lysine 5,6-aminomutase () is an enzyme that catalyzes the chemical reaction
D-lysine 2,5-diaminohexanoate
Hence, this enzyme has one substrate, D-lysine, and one product, 2,5-diaminohexanoate.
This enzyme participates in lysine degradation. It employs one cofactor, cobamide.
Background
D-lysine 5,6-aminomutase belongs to the isomerase family of enzymes, specifically intramolecular transferases, which transfers amino groups. Its systematic name is D-2,6-diaminohexanoate 5,6-aminomutase. Other names in common use include D-α-lysine mutase and adenosylcobalamin-dependent D-lysine 5,6-aminomutase, which can be abbreviated as 5,6-LAM.
5,6-LAM is capable of reversibly catalyzing the migration of an amino group from ε-carbon to δ-carbon in both D-lysine and L-β-lysine, and catalyzing the migration of hydrogen atoms from δ-carbon to ε-carbon at the same time. It demonstrates greatest catalytic activity in 20mM Tris•HCl at pH 9.0-9.2.
In the early 1950s, 5,6-LAM was discovered in the amino-acid-fermenting bacteria Clostridium sticklandii, in which lysine undergoes degradation under anaerobic conditions to equimolar amounts of acetate and butyrate.
Later, isotopic studies uncovered two possible pathways. In pathway A, both acetate and butyrate are generated from C2-C3 cleavage of D-lysine. Unlike pathway A, pathway B involves C5-C4 degradation, producing the same products.
D-lysine 5,6-aminomutase (5,6-LAM) is responsible for the first conversion in pathway B to convert D-α-lysine into 2,5-diaminohexanoate. Unlike other members of the family of aminomutases (like 2,3-LAM), which are peculiar to a single substrate, 5,6-LAM can reversibly catalyze both the reaction of D-lysine to 2,5-diaminohexanoic acid and the reaction of L-β-lysine to 3,5-diaminohexanoic acid.
Structure
Subunits
5,6-LAM is an α2β2 tetramer. The structure of the alpha subunit is predominantly a PLP-binding TIM barrel domain, with several additional alpha-helices and beta-strands at the N and C termini. These helices and strands form an intertwined accessory clamp structure that wraps around the sides of the TIM barrel and extends up toward the Ado ligand of the Cbl cofactor, which is the beta subunit providing most of the interactions observed between the protein and the Ado ligand of the Cbl, suggesting that its role is mainly in stabilizing AdoCbl in the precatalytic resting state. The β subunit binds AdoCbl while the PLP directly binds to α subunit. PLP also directly binds to Lys144 of the β subunit to form an internal aldimine. PLP and AdoCbl are separated by a distance of 24Å.
Cofactors
5,6-LAM is pyridoxal-5'-phosphate (PLP) dependent. PLP binds to its substrate with an external aldimine linkage. PLP is also important for stabilizing the radical intermediate by captodative stabilization and spin delocalization.
Catalysis begins with a 5'-deoxyadenosyl radical (Ado-CH2•), and 5'-deoxyadenosylcobalamin (AdoCbl) is an essential cofactor as a hydrogen carrier.
ATP, a mercaptan, and a divalent metal ion (usually Mg2+) are required to achieve the highest catalytic effect.
Mechanism
Catalytic cycle
The catalytic cycle starts with Ado-CH2• (5'-deoxyadenosyl radical derived from adenosylcobalamine) abstracting a hydrogen atom from PLP-D-lysine adduct (substrate-related precursor SH) to generate a substrate-related radical (S•), with the radical located at carbon 5 of the lysine residue. The latter undergoes an internal cyclization/addition to the imine nitrogen producing an aziridinecarbinyl radical (I•) — a more thermodynamically stable intermediate with the radical being at a benzylic position. Rearrangement of I• produces a product-related radical (P•), which then participates in the final step of hydrogen transfer from AdoH to afford the PLP-product complex (PH).
Structure-based catalysis
Further understanding of the catalytic mechanism can be derived from the X-ray structure.
First, an evident conformational change is observed after the substrate is added to the system. With a substrate-free enzyme, the distance between AdoCbl and PLP is about 24 Å. PLP participates in multiple non-covalent interactions with the enzyme with 5,6-LAM presenting an “open” state.
The first step of the catalytic cycle involves the enzyme accepting the substrate by forming an external aldimine with PLP replacing the PLP-Lys144β internal aldimine. With the cleavage of the internal aldimine, the β unit is able to swing towards to the top of the α unit and block the empty site. Therefore, generation of the Ado-CH2• radical leads to a change in the structure of the active domain, bringing the AdoCbl and PLP-substrate complex closer to each other, thus locking the enzyme in a “closed” state. The closed state exists until the radical transfer occurs when the product is released and AdoCbl is reformed. At the same time, the closed state is transformed to the open state again to wait for the next substrate.
Also worth mentioning is the locking mechanism to prevent the radical reaction without the presence of substrate discovered by Catherine Drennan's group. Lys144 of the β subunit is located at a short G-rich loop highly conserved across all 5,6-LAMs, which blocks the AdoCbl from the reaction site. Based on X-ray structure analysis, when the open structure is applied, the axes of the TIM barrel and Rossmann domains are in different directions. With the addition of the substrate, the subunits rearrange to turn the axes into each other to facilitate the catalysis. For example, in wild type 5,6-LAM, the phenol ring of Tyr263α is oriented in a slipped geometry with pyridine ring of PLP, generating a π-π stacking interaction, which is capable of modulating the electron distribution of the high-energetic radical intermediate.
History
Early insights into the mechanism of the catalytic reaction mainly focused on isotopic methods. Both pathways of lysine degradation and the role of 5,6-LAM were discovered in early work by Stadtman's group during 1950s-1960s. In 1971, having a tritiated α-lysine, 2,5-diaminohexanoate, and coenzyme in hand, Colin Morley and T. Stadtman discovered the role of 5'-deoxyadenosylcobalamin (AdoCbl) as a source for hydrogen migration. Recently, much progress has been made toward detecting the intermediates of the reaction, especially towards I•. Based on quantum-mechanical calculations, it was proposed that with 5-fluorolysine as a substitute for D-lysine the 5-FS• species can be captured and analyzed. A similar approach was applied towards PLP modification, when it was modified to 4’-cyanoPLP or PLP-NO. The radical intermediate I• analogue is hypothesized to be easily detected to support the proposed mechanism. Other simulations can also provide some insights into the catalytic reaction.
References
Protein domains
EC 5.4.3
Cobamide enzymes
Enzymes of unknown structure | D-lysine 5,6-aminomutase | Biology | 1,749 |
4,760,719 | https://en.wikipedia.org/wiki/Jeffrey%20P.%20Buzen | Jeffrey Peter Buzen (born May 28, 1943) is an American computer scientist in system performance analysis best known for his contributions to queueing theory. His PhD dissertation (available as https://archive.org/details/DTIC_AD0731575) and his 1973 paper Computational algorithms for closed queueing networks with exponential servers have guided the study of queueing network modeling for decades.
Born in Brooklyn, Buzen holds three degrees in Applied Mathematics -- an ScB (1965) from Brown University and, from Harvard University, an MS (1966) and a PhD (1971). He was a systems programmer at the National Institutes of Health in Bethesda, Maryland (1967–69), where his technique for optimizing the performance of a realtime biomedical computer system led to his first publication at a 1969 IEEE conference. After completing his PhD, he held concurrent appointments as a lecturer in computer science at Harvard and as a systems engineer at Honeywell (1971-76). Some of his students at Harvard have gone on to become well-known figures in computing. Buzen was PhD thesis advisor for Robert M. Metcalfe (1973), Turing Award winner and co-inventor of Ethernet, and for John M. McQuillan (1974), developer the original adaptive routing algorithms used in ARPAnet and Internet. Buzen also co-taught (with Ugo Gagliardi) a two-semester graduate-level course on operating systems (AM 251a/AM251br) that Microsoft co-founder Bill Gates took during his freshman year (1973-74). Two decades later, Gates wrote "It was the only 'computer course' I officially ever took at Harvard." (private email, July 24, 1995)
In addition to being an educator and a researcher, Buzen is also an entrepreneur. Along with fellow Harvard applied mathematics PhDs Robert Goldberg and Harold Schwenk, he co-founded BGS Systems in 1975. The company, which began operations in his basement, developed, marketed and supported software products for the performance management and capacity planning of enterprise computer systems. Their flagship modeling product, BEST/1, was based on proprietary extensions to the queuing network models and computational algorithms that Buzen developed in his PhD thesis.
BGS Systems was listed on NASDAQ (BGSS) from 1983 to 1998. Buzen served as chief scientist and senior vice president until the company was acquired by BMC Software in 1998.
In addition to the development of specific models and algorithms, Buzen’s research has also dealt extensively with the question of why some stochastic models work surprisingly well in practice, even though the theoretical assumptions upon which these models are based seem unlikely to be satisfied by real world systems. This has led the development of an alternative approach to stochastic modeling that makes it possible to derive certain classical results using simpler assumptions that are more likely to be satisfied in practice. His initial 1976 paper on this topic Fundamental Laws of Computer System Performance received the inaugural ACM Sigmetrics “Test of Time Award” in 2010, reflecting 34 years of enduring influence. His 2016 book Rethinking Randomness extends this work further and presents a generalized modeling framework he refers to as observational stochastics.
Buzen has held leadership positions in various professional societies, including Association for Computing Machinery Sigmetrics, the International Federation for Information Processing Working Group 7.3, and the Computer Measurement Group (serving as president during 2000–2001). In 1979, he received Computer Measurement Group's A.A. Michelson award for technical excellence and professional contributions as a teacher and inspirer of others. He also received the ACM SIGMETRICS Achievement Award in 2010.
He was elected a member of the National Academy of Engineering in 2003 for contributions to the theory and commercial application of computer system performance models.
See also
Buzen's algorithm
References
External links
Short biography
List of publications
1943 births
American computer scientists
Brown University alumni
Computer systems engineers
Harvard University alumni
Scientists from Brooklyn
Queueing theorists
Living people
Members of the United States National Academy of Engineering
Scientists from New York (state) | Jeffrey P. Buzen | Technology | 847 |
64,056,942 | https://en.wikipedia.org/wiki/Institute%20for%20Disease%20Modeling | Institute for Disease Modeling (IDM) is an institute within the Global Health Division of the Bill and Melinda Gates Foundation. Established in 2008 as part of the Global Good Fund, a non-profit subsidiary of Intellectual Ventures (IV) funded by Bill and Melinda Gates, IDM has transitioned in mid-2020 to the Gates Foundation.
IDM specializes in mathematical modelling of infectious disease and other quantitative global health research. Its models include malaria, polio, measles, COVID-19 and HIV (with EMOD). IDM releases source code of their stable models to the public. While at IV, the institute was located in Bellevue, Washington. After the outbreak of COVID-19 in Washington State, IDM has transitioned to all-remote work with no physical offices. It will eventually relocate to the Gates Foundation's main office in Seattle.
Disease modeling software
EMOD is the group's individual-based disease modeling software (not a compartmental model) initially coded 2005. It has been released to the public as open-source software. The software can model malaria, HIV, tuberculosis, measles, dengue, polio and typhoid.
In 2020, IDM developed a designated COVID-19 agent-based model named "Covasim." It was used initially to advise on decision-making during the COVID-19 pandemic in Oregon and in Washington State, gaining national attention. Covasim, coded in Python, is open-source and has been used by independent researchers around the world.
References
Sources
External links
COVID-19 Chapter 11: Modeling, This Podcast Will Kill You, May 4, 2020, interview with Dr. Mike Famulare from the Institute for Disease Modeling recorded April 29, 2020 starts at 28:30
Companies based in Bellevue, Washington
Epidemiology
Simulation software | Institute for Disease Modeling | Environmental_science | 376 |
16,883,797 | https://en.wikipedia.org/wiki/SHINE%20Expert%20System | Spacecraft Health Inference Engine (SHINE) is a software-development tool for knowledge-based systems, created by the Artificial intelligence Group, Information Systems Technology Section at NASA/JPL. The system is in use in basic and applied AI research at JPL. SHINE was designed to operate in a real-time environment. It is written in Common LISP, but able to be utilized by non-LISP applications written in conventional programming languages such as C and C++. These non-LISP applications can be running in a distributed computing environment on remote computers or on a computer that supports multiple programming languages. SHINE provides a variety of facilities for the development of software modules for the primary functions in knowledge-based reasoning engines. The system may be used to develop artificial intelligence applications as well as specialized tools for research efforts.
Background
The original inventors of SHINE are Mark L. James and David J. Atkinson. SHINE is an expert system and inference engine based upon the experience, requirements and technology that were collected by the Artificial Intelligence Research group at NASA/JPL in developing expert systems for the diagnosis of spacecraft health. SHINE is based on technology first developed by James and Atkinson for the "STAR*TOOL" system. SHINE itself resulted from applying this technology in a project called "Spacecraft Health Automated Reasoning Pilot" (SHARP). SHARP aimed to automate and provide expert system consultation to space flight operations personnel who monitor and diagnose robotic spacecraft on science missions, such as the Voyager spacecraft.
SHINE is written in Common LISP and can be run on any system that supports the language. It has been interfaced with many non-LISP systems.
Beyond Limits has the Caltech licensing rights to all commercial applications of SHINE.
Historical and current applications of SHINE
Spacecraft Health Automatic Reasoning Pilot (SHARP) for the diagnosis of telecommunication anomalies during the Neptune Voyager (VGR) Encounter.
Galileo's (GLL) mission for diagnosing problems in the Power and Pyro Subsystem (PPS).
Magellan's (MGN) mission for diagnosis of telecommunication anomalies in the TELECOM subsystem.
Engineering Analysis Subsystem Environment (EASE) which is an operations environment to operate a large number of spacecraft simultaneously and increase productivity through shared resources and automation.
Extreme Ultra Violet Explorer (EUVE) mission for labour 3 to 1 shift reductions through the use of artificial intelligence.
Fault Induced Document Officer (FIDO) for the EUVE mission. which is an automated system that assists in expert knowledge acquisition, access and publishing capabilities for safely managing complex systems under staffing reductions and "lights out" operations.
Stochastic Problem Obviation Tracker (SPOT) for the EUVE mission which captures and reports relevant statistical information to the user based on operations within the FIDO environment.
The Program is licensed by Beyond Limits for use with their artificial intelligence technology.
Under consideration by a medical company for real-time diagnosis of rectal colon cancer.
Under consideration by a medical company for an expert system for the control of the robotic systems used in eye surgery.
External links
Software Analyses Complex Systems in Real Time
SHINE use at NASA
SHINE was previously licensed to Viaspace for commercial purposes
SHINE: The Spacecraft Health Interface Engine
References
Expert systems
Common Lisp (programming language) software | SHINE Expert System | Technology | 663 |
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