Ulrich Müller
- Published in print:
- 2013
- Published Online:
- December 2013
- ISBN:
- 9780199669950
- eISBN:
- 9780191775086
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199669950.003.0001
- Subject:
- Physics, Crystallography: Physics, Condensed Matter Physics / Materials
This introductory chapter outlines the symmetry principle in crystal chemistry states: in crystal structures the arrangement of the atoms has a tendency towards the highest possible symmetry; ...
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This introductory chapter outlines the symmetry principle in crystal chemistry states: in crystal structures the arrangement of the atoms has a tendency towards the highest possible symmetry; counteracting factors may enforce a reduced symmetry; and during phase transitions and topotactic reactions which result in products of lower symmetry, the higher symmetry of the starting material is often indirectly preserved by the formation of oriented domains. Many crystal structures can be derived from a few simple, highly symmetrical crystal structures. A family of structures is headed by a most symmetrical structure — the aristotype — and the space groups of the derivative structures or hettotypes are subgroups of the space group of the aristotype. A Bärnighausen tree depicts the group-subgroup relations. An example is the relation diamond-zinc blende. Symmetry reduction to a subgroup can take place during a phase transition, and a twinned crystal can be the result.Less
This introductory chapter outlines the symmetry principle in crystal chemistry states: in crystal structures the arrangement of the atoms has a tendency towards the highest possible symmetry; counteracting factors may enforce a reduced symmetry; and during phase transitions and topotactic reactions which result in products of lower symmetry, the higher symmetry of the starting material is often indirectly preserved by the formation of oriented domains. Many crystal structures can be derived from a few simple, highly symmetrical crystal structures. A family of structures is headed by a most symmetrical structure — the aristotype — and the space groups of the derivative structures or hettotypes are subgroups of the space group of the aristotype. A Bärnighausen tree depicts the group-subgroup relations. An example is the relation diamond-zinc blende. Symmetry reduction to a subgroup can take place during a phase transition, and a twinned crystal can be the result.
Gordon L. Fain
- Published in print:
- 2019
- Published Online:
- December 2019
- ISBN:
- 9780198835028
- eISBN:
- 9780191872846
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780198835028.003.0007
- Subject:
- Biology, Neurobiology, Biochemistry / Molecular Biology
“Chemoreception and the sense of smell” is the seventh chapter of the book Sensory Transduction and begins with a general description of chemoreception, including chemotaxis in bacteria. It then ...
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“Chemoreception and the sense of smell” is the seventh chapter of the book Sensory Transduction and begins with a general description of chemoreception, including chemotaxis in bacteria. It then describes olfaction in insects, including new discoveries of the nature of insect receptor proteins and the coding of olfaction in insects. It proceeds to review olfaction in vertebrates, beginning with the primary olfactory epithelium. It describes olfactory receptor proteins, the mechanism of olfactory transduction, and pathways of desensitization and adaptation. The basis of coding in the principal olfactory epithelium is described together with the anatomy and physiology of the olfactory bulb. A final section is provided on the accessory olfactory system and vomeronasal organ, including a description of receptor proteins, transduction cascades, and wiring to the accessory olfactory bulbs.Less
“Chemoreception and the sense of smell” is the seventh chapter of the book Sensory Transduction and begins with a general description of chemoreception, including chemotaxis in bacteria. It then describes olfaction in insects, including new discoveries of the nature of insect receptor proteins and the coding of olfaction in insects. It proceeds to review olfaction in vertebrates, beginning with the primary olfactory epithelium. It describes olfactory receptor proteins, the mechanism of olfactory transduction, and pathways of desensitization and adaptation. The basis of coding in the principal olfactory epithelium is described together with the anatomy and physiology of the olfactory bulb. A final section is provided on the accessory olfactory system and vomeronasal organ, including a description of receptor proteins, transduction cascades, and wiring to the accessory olfactory bulbs.
