Heterocyclic Compounds: Ring compounds having atoms other than carbon in their nuclei. (Grant & Hackh's Chemical Dictionary, 5th ed)Heterocyclic Compounds, Bridged-Ring: A class of organic compounds which contain two rings that share a pair of bridgehead carbon atoms.Nitrogen Compounds: Inorganic compounds that contain nitrogen as an integral part of the molecule.Cyclization: Changing an open-chain hydrocarbon to a closed ring. (McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)Heterocyclic Compounds, 2-Ring: A class of organic compounds containing two ring structures, one of which is made up of more than one kind of atom, usually carbon plus another atom. The heterocycle may be either aromatic or nonaromatic.Palladium: A chemical element having an atomic weight of 106.4, atomic number of 46, and the symbol Pd. It is a white, ductile metal resembling platinum, and following it in abundance and importance of applications. It is used in dentistry in the form of gold, silver, and copper alloys.Heterocyclic Compounds with 4 or More Rings: A class of organic compounds containing four or more ring structures, one of which is made up of more than one kind of atom, usually carbon plus another atom. The heterocycle may be either aromatic or nonaromatic.Heterocyclic Compounds, 3-Ring: A class of organic compounds containing three ring structures, one of which is made up of more than one kind of atom, usually carbon plus another atom. The heterocycle may be either aromatic or nonaromaticMolecular Structure: The location of the atoms, groups or ions relative to one another in a molecule, as well as the number, type and location of covalent bonds.Heterocyclic Compounds, 1-Ring: A class of organic compounds containing a ring structure made up of more than one kind of atom, usually carbon plus another atom. The ring structure can be aromatic or nonaromatic.Magnetic Resonance Spectroscopy: Spectroscopic method of measuring the magnetic moment of elementary particles such as atomic nuclei, protons or electrons. It is employed in clinical applications such as NMR Tomography (MAGNETIC RESONANCE IMAGING).Encyclopedias as Topic: Works containing information articles on subjects in every field of knowledge, usually arranged in alphabetical order, or a similar work limited to a special field or subject. (From The ALA Glossary of Library and Information Science, 1983)Chemistry, Organic: The study of the structure, preparation, properties, and reactions of carbon compounds. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Furans: Compounds with a 5-membered ring of four carbons and an oxygen. They are aromatic heterocycles. The reduced form is tetrahydrofuran.ThiophenesAcids, Carbocyclic: Carboxylic acids that have a homocyclic ring structure in which all the ring atoms are carbon.Methane: The simplest saturated hydrocarbon. It is a colorless, flammable gas, slightly soluble in water. It is one of the chief constituents of natural gas and is formed in the decomposition of organic matter. (Grant & Hackh's Chemical Dictionary, 5th ed)Stereoisomerism: The phenomenon whereby compounds whose molecules have the same number and kind of atoms and the same atomic arrangement, but differ in their spatial relationships. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)Alkenes: Unsaturated hydrocarbons of the type Cn-H2n, indicated by the suffix -ene. (Grant & Hackh's Chemical Dictionary, 5th ed, p408)IminesCatalysis: The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction.Fungicides, Industrial: Chemicals that kill or inhibit the growth of fungi in agricultural applications, on wood, plastics, or other materials, in swimming pools, etc.AcetalsHalogens: A family of nonmetallic, generally electronegative, elements that form group 17 (formerly group VIIa) of the periodic table.Quaternary Ammonium Compounds: Derivatives of ammonium compounds, NH4+ Y-, in which all four of the hydrogens bonded to nitrogen have been replaced with hydrocarbyl groups. These are distinguished from IMINES which are RN=CR2.Quantitative Structure-Activity Relationship: A quantitative prediction of the biological, ecotoxicological or pharmaceutical activity of a molecule. It is based upon structure and activity information gathered from a series of similar compounds.Tetraoxanes: Compounds with two peroxide groups, that is, two pairs of adjacent OXYGEN atoms. They may have activity against PLASMODIUM similar to the ARTEMISININS.Pyridinium CompoundsSalts: Substances produced from the reaction between acids and bases; compounds consisting of a metal (positive) and nonmetal (negative) radical. (Grant & Hackh's Chemical Dictionary, 5th ed)Microbial Sensitivity Tests: Any tests that demonstrate the relative efficacy of different chemotherapeutic agents against specific microorganisms (i.e., bacteria, fungi, viruses).Anti-Bacterial Agents: Substances that reduce the growth or reproduction of BACTERIA.Quantum Theory: The theory that the radiation and absorption of energy take place in definite quantities called quanta (E) which vary in size and are defined by the equation E=hv in which h is Planck's constant and v is the frequency of the radiation.Chemistry, Inorganic: A field of chemistry which pertains to chemical compounds or ions that do not contain the element carbon (with the exception of carbon dioxide and compounds containing a carbonate radical, e.g., calcium carbonate).Corrosion: The gradual destruction of a metal or alloy due to oxidation or action of a chemical agent. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Models, Chemical: Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.Coitus Interruptus: A contraceptive method whereby coitus is purposely interrupted in order to prevent EJACULATION of SEMEN into the VAGINA.EuropeSpiro Compounds: A group of compounds consisting in part of two rings sharing one atom (usually a carbon) in common.Oxazolone: Immunologic adjuvant and sensitizing agent.Androstenediol: An intermediate in TESTOSTERONE biosynthesis, found in the TESTIS or the ADRENAL GLANDS. Androstenediol, derived from DEHYDROEPIANDROSTERONE by the reduction of the 17-keto group (17-HYDROXYSTEROID DEHYDROGENASES), is converted to TESTOSTERONE by the oxidation of the 3-beta hydroxyl group to a 3-keto group (3-HYDROXYSTEROID DEHYDROGENASES).Androstenediols: Unsaturated androstane derivatives which are substituted with two hydroxy groups in any position in the ring system.Pyrazoles: Azoles of two nitrogens at the 1,2 positions, next to each other, in contrast with IMIDAZOLES in which they are at the 1,3 positions.Cholestadienols: Cholestadiene derivatives containing a hydroxy group anywhere in the molecule.Dehydroepiandrosterone: A major C19 steroid produced by the ADRENAL CORTEX. It is also produced in small quantities in the TESTIS and the OVARY. Dehydroepiandrosterone (DHEA) can be converted to TESTOSTERONE; ANDROSTENEDIONE; ESTRADIOL; and ESTRONE. Most of DHEA is sulfated (DEHYDROEPIANDROSTERONE SULFATE) before secretion.BooksBeggiatoa: A genus of colorless, filamentous bacteria in the family THIOTRICHACEAE whose cells contain inclusions of sulfur granules. When found in decaying seaweed beds and polluted water, its presence signals environmental degradation.Antimitotic Agents: Agents that arrest cells in MITOSIS, most notably TUBULIN MODULATORS.Carbon: A nonmetallic element with atomic symbol C, atomic number 6, and atomic weight [12.0096; 12.0116]. It may occur as several different allotropes including DIAMOND; CHARCOAL; and GRAPHITE; and as SOOT from incompletely burned fuel.Carbon Compounds, Inorganic: Inorganic compounds that contain carbon as an integral part of the molecule but are not derived from hydrocarbons.Diphosphonates: Organic compounds which contain P-C-P bonds, where P stands for phosphonates or phosphonic acids. These compounds affect calcium metabolism. They inhibit ectopic calcification and slow down bone resorption and bone turnover. Technetium complexes of diphosphonates have been used successfully as bone scanning agents.Patents as Topic: Exclusive legal rights or privileges applied to inventions, plants, etc.Geranyltranstransferase: An enzyme involved in the MEVALONATE pathway, it catalyses the synthesis of farnesyl diphosphate from isopentenyl diphosphate and dimethylallyl diphosphate.Alendronate: A nonhormonal medication for the treatment of postmenopausal osteoporosis in women. This drug builds healthy bone, restoring some of the bone loss as a result of osteoporosis.