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Hydrogen-depleted Molecular Graph
In chemical graph theory and in mathematical chemistry, a molecular graph or chemical graph is a representation of the structural formula of a chemical compound in terms of graph theory. A chemical graph is a labeled graph whose vertices correspond to the atoms of the compound and edges correspond to chemical bonds. Its vertices are labeled with the kinds of the corresponding atoms and edges are labeled with the types of bonds. For particular purposes any of the labelings may be ignored. A hydrogen-depleted molecular graph or hydrogen-suppressed molecular graph is the molecular graph with hydrogen vertices deleted. In some important cases (topological index calculation etc.) the following classical definition is sufficient: a molecular graph is a connected, undirected graph which admits a one-to-one correspondence with the structural formula of a chemical compound in which the vertices of the graph correspond to atoms of the molecule and edges of the graph correspond to chemical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caffeine Structure
Caffeine is a central nervous system (CNS) stimulant of the methylxanthine class and is the most commonly consumed psychoactive substance globally. It is mainly used for its eugeroic (wakefulness promoting), ergogenic (physical performance-enhancing), or nootropic (cognitive-enhancing) properties. Caffeine acts by blocking the binding of adenosine at a number of adenosine receptor types, inhibiting the centrally depressant effects of adenosine and enhancing the release of acetylcholine. Caffeine has a three-dimensional structure similar to that of adenosine, which allows it to bind and block its receptors. Caffeine also increases cyclic AMP levels through nonselective inhibition of phosphodiesterase, increases calcium release from intracellular stores, and antagonizes GABA receptors, although these mechanisms typically occur at concentrations beyond usual human consumption. Caffeine is a bitter, white crystalline purine, a methylxanthine alkaloid, and is chemically related ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Graph Theory, 1736–1936
''Graph Theory, 1736–1936'' is a book in the history of mathematics on graph theory. It focuses on the foundational documents of the field, beginning with the 1736 paper of Leonhard Euler on the Seven Bridges of Königsberg and ending with the first textbook on the subject, published in 1936 by Dénes Kőnig. ''Graph Theory, 1736–1936'' was edited by Norman L. Biggs, E. Keith Lloyd, and Robin J. Wilson, and published in 1976 by the Clarendon Press. The Oxford University Press published a paperback second edition in 1986, with a corrected reprint in 1998. Topics ''Graph Theory, 1736–1936'' contains copies, extracts, and translations of 37 original sources in graph theory, grouped into ten chapters and punctuated by commentary on their meaning and context. It begins with Euler's 1736 paper "Solutio problematis ad geometriam situs pertinentis" on the seven bridges of Königsberg (both in the original Latin and in English translation) and ending with Dénes Kőnig's book ''T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mathematical Chemistry
Mathematical chemistry is the area of research engaged in novel applications of mathematics to chemistry; it concerns itself principally with the mathematical modeling of chemical phenomena. Mathematical chemistry has also sometimes been called computer chemistry, but should not be confused with computational chemistry. Major areas of research in mathematical chemistry include chemical graph theory, which deals with topology such as the mathematical study of isomerism and the development of topological descriptors or indices which find application in quantitative structure-property relationships; and chemical aspects of group theory, which finds applications in stereochemistry and quantum chemistry. Another important area is molecular knot theory and circuit topology that describe the topology of folded linear molecules such as proteins and nucleic acids. The history of the approach may be traced back to the 19th century. Georg Helm published a treatise titled "The Principles ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theoretical Chemistry
Theoretical chemistry is the branch of chemistry which develops theoretical generalizations that are part of the theoretical arsenal of modern chemistry: for example, the concepts of chemical bonding, chemical reaction, valence, the surface of potential energy, molecular orbitals, orbital interactions, and molecule activation. Overview Theoretical chemistry unites principles and concepts common to all branches of chemistry. Within the framework of theoretical chemistry, there is a systematization of chemical laws, principles and rules, their refinement and detailing, the construction of a hierarchy. The central place in theoretical chemistry is occupied by the doctrine of the interconnection of the structure and properties of molecular systems. It uses mathematical and physical methods to explain the structures and dynamics of chemical systems and to correlate, understand, and predict their thermodynamic and kinetic properties. In the most general sense, it is explanation o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Substructure Search
Substructure search (SSS) is a method to retrieve from a Chemical database, database only those Chemical compound, chemicals matching a pattern of atoms and bonds which a user specifies. It is an application of graph theory, specifically subgraph matching in which the query is a hydrogen-depleted molecular graph. The mathematical foundations for the method were laid in the 1870s, when it was suggested that Molecule editor, chemical structure drawings were equivalent to graphs with atoms as vertices and bonds as edges. SSS is now a standard part of cheminformatics and is widely used by pharmaceutical chemists in drug discovery. There are many commercial systems that provide SSS, typically having a graphical user interface and chemical drawing software. Large publicly-available databases like PubChem and ChemSpider can be searched this way, as can Wikipedia's articles describing individual chemicals. Definitions Substructure search is used to retrieve from a chemical database, data ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Simplified Molecular-input Line-entry System
Simplification, Simplify, or Simplified may refer to: Mathematics Simplification is the process of replacing a expression (mathematics), mathematical expression by an equivalent one that is simpler (usually shorter), according to a well-founded ordering. Examples include: * Computer algebra#Simplification, Simplification of algebraic expressions, in computer algebra * Simplification of boolean expressions i.e. logic optimization * Simplification by conjunction elimination in inference in logic yields a simpler, but generally non-equivalent formula * Fraction#Simplification, Simplification of fractions Science * Approximations simplify a more detailed or difficult to use process or model Linguistics * Simplification of Chinese characters * Simplified English (other) * Text simplification Music * ''Simplify'', a 1999 album by Ryan Shupe & the RubberBand * Simplified (band), a 2002 rock band from Charlotte, North Carolina * Simplified (album), ''Simplified'' (album), a 2005 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Graph Generator
A chemical graph generator is a software package to generate computer representations of chemical structures adhering to certain Boundary value problem, boundary conditions. The development of such software packages is a research topic of cheminformatics. Chemical graph generators are used in areas such as virtual Chemical library, library generation in drug design, in Molecular model, molecular design with specified properties, called inverse Quantitative structure–activity relationship, QSAR/QSPR, as well as in organic synthesis, organic synthesis design, Retrosynthetic analysis, retrosynthesis or in systems for computer-assisted structure elucidation (CASE). CASE systems again have regained interest for the structure elucidation of unknowns in computational metabolomics, a current area of computational biology. History Molecular structure generation is a branch of Graph (discrete mathematics), graph generation problems. Molecular structures are graphs with chemical constrain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Higgins (chemist)
William Higgins (1763 – June 1825), an Irish chemist, was one of the early proponents of atomic theory. Known mainly for his speculative ideas on chemical combination, William Higgins is popular for the insights his life offers into the emergence of chemistry as a career during the British Industrial Revolution. Despite an evident charm, his erratic behaviour and tendency to indulge personal animosities prevented him from engaging the affections of London society. Instead he found refuge in a succession of government-supported chemical positions in Dublin. Thanks to the combination of such scientific opportunities with family resources, he became a very wealthy man. Early years Higgins was born in Collooney, County Sligo, Ireland, and came from a well-known medical family. William was the second child and younger son of Thomas Higgins, a physician educated at the University of Edinburgh. William’s uncle Bryan Higgins was also an eminent chemist. When William was a b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Cullen
William Cullen (; 15 April 17105 February 1790) was a British physician, chemist and agriculturalist from Hamilton, Scotland, who also served as a professor at the Edinburgh Medical School. Cullen was a central figure in the Scottish Enlightenment: He was David Hume's physician, and was friends with Joseph Black, Henry Home, Adam Ferguson, John Millar, and Adam Smith, among others. He was president of the Royal College of Physicians and Surgeons of Glasgow (1746–47), president of the Royal College of Physicians of Edinburgh (1773–1775) and first physician to the king in Scotland (1773–1790). He also assisted in obtaining a royal charter for the Philosophical Society of Edinburgh, resulting in the formation of the Royal Society of Edinburgh in 1783. Cullen was a beloved teacher, and many of his students became influential figures. He kept in contact with many of his students, including Benjamin Rush, a central figure in the founding of the United States of Americ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravity
In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force between objects and the Earth. This force is dominated by the combined gravitational interactions of particles but also includes effect of the Earth's rotation. Gravity gives weight to physical objects and is essential to understanding the mechanisms responsible for surface water waves and lunar tides. Gravity also has many important biological functions, helping to guide the growth of plants through the process of gravitropism and influencing the circulation of fluids in multicellular organisms. The gravitational attraction between primordial hydrogen and clumps of dark matter in the early universe caused the hydrogen gas to coalesce, eventually condensing and fusing to form stars. At larger scales this results in galaxies and clust ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isaac Newton
Sir Isaac Newton () was an English polymath active as a mathematician, physicist, astronomer, alchemist, theologian, and author. Newton was a key figure in the Scientific Revolution and the Age of Enlightenment, Enlightenment that followed. His book (''Mathematical Principles of Natural Philosophy''), first published in 1687, achieved the Unification of theories in physics#Unification of gravity and astronomy, first great unification in physics and established classical mechanics. Newton also made seminal contributions to optics, and Leibniz–Newton calculus controversy, shares credit with German mathematician Gottfried Wilhelm Leibniz for formulating calculus, infinitesimal calculus, though he developed calculus years before Leibniz. Newton contributed to and refined the scientific method, and his work is considered the most influential in bringing forth modern science. In the , Newton formulated the Newton's laws of motion, laws of motion and Newton's law of universal g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
