Definition of torus in English:

torus

nounPlural toruses, Plural tori ˈtɔːrəsˈtɔrəs

1Geometry
A surface or solid formed by rotating a closed curve, especially a circle, about a line which lies in the same plane but does not intersect it (e.g. like a ring doughnut).
〔几何〕环形圆纹曲面，环面，锚环
Example sentencesExamples
- You can see a movie of a flat surface becoming a torus at this page about Paper Strip Activities.
- A small patch of a sphere or torus surface looks almost like a piece of a flat plane and has area rather than volume.
- ‘It appears the torus is rotating like a wheel,’ she continued.
- Into how many pieces can one cut a torus using two planes?
- ‘In other words, each solution could be drawn on the surface of a torus,’ he notes.
- To avoid edge effects, the lattice is represented on a circle for a one-dimensional model or a torus for a two-dimensional model.
- The resulting surface is a two-manifold called a torus.
- Because the two periods are not related by an integer but are incommensurate, the system does not flow toward a closed path but instead orbits without converging on the surface of the torus.
- A bagel can serve as a physical model for a mathematical surface called a torus.
- Intuitively, this is a consequence of the fact that two lineages can be functionally separated by a greater distance in a rectangle than in a torus.
- We can also represent the flat hexagonal torus as a tiling of flat space, as in fig.9.
- The surface of a sphere is a good example, as is a torus (the mathematical name for the shape of the surface of a quoit, or a ring-shaped doughnut).
- I found there that the solution of Archytus involves three surfaces - torus, cylinder, and cone.
- There are three classical attractors, a point which characterises a steady state system, a closed loop which characterises a periodic system, and a torus which combines several cycles.
- The surface area of the inside portion of a torus can be obtained by integrating Eq. 4, which yields
- The Clifford torus is generated by a family of circles.
- ‘And it stands to reason that they would have other toruses dotting the quadrant,’ Maria speculated.
- To be rigorous, the hole is not actually in the torus: the torus is the surface and the hole is in the space around the surface.
- In the formula of the curve given above the torus is formed from a circle of radius a whose centre is rotated along a circle of radius r.
- All the quasi-fuchsian subgroups correspond to pairs of once-punctured tori, but as one tends to the boundary a certain curve on one of the tori may get squeezed to a point.
1. 1.1 A ring-shaped object, especially a large ring-shaped chamber used in physical research.
  环形物（尤指开展物理研究的大型环形室）
  Example sentencesExamples
  The downfield resonance is attributed to molecules (mostly DCPC) on the highly curved region of the bicelle torus.
  A set of six hoop coils around the outside of the machine produces the magnetic field that shapes and positions the plasma centrally in the torus.
  The defense platform was a torus with three large solar panel arrays extending out from it with 120 degrees between them.
  When a neutron star binary coalesces, the rapidly spinning merged system is expected to form a spinning black hole, orbited momentarily by a torus of neutron-density matter.
  ‘He's good,’ Maria said as she angled the ship to orbit the torus.
  It is possible that in this scan area the vesicles were not well dispersed; however, we cannot discount the possibility of irregular shapes being formed in addition to the torus and horseshoe shapes.
  Nat Fisch of Princeton University and his colleagues propose driving the current by adding energy in only a small region, rather than everywhere around the torus.
  Hence the results presented for the torus will have general relevance for vestibular channels.
  Mark wondered why the rotating torus wasn't crushed from the tremendous gravitational forces at the mouth of the wormhole.
  Like tokamaks, their currently more advanced cousins, stellarators use magnetic fields to confine plasma in a torus for fusion reactions.
  The shuttle left the station at the same time that the invisible ship, the Sentinel, left their orbit for the torus.
  The ships were built around a torus shaped Spacial-Warp core.
  By carefully accounting for the particles injected into the machine and for those exhausted in the pumping system we found a deficit, indicating that a large fraction of deuterium gets trapped in the walls and components inside the torus.
  The floor curved more gradually along the torus, so that the rows of apple and plum trees seemed to rise up on the side of a rolling hill, above the top of the nearby hay, until they disappeared in the horizon defined by the artificial sunlight.
  The Constitution fired one shot from a single turret, blasting a hole into one side of the torus that formed the bulk of the station.
  This remarkable device consists of a torus of alternating magnetic materials that are chosen so that the torus has a huge net spin - 10 22 aligned electron spins - yet produces no magnetic field.
  The innermost sections have the shape of a torus, but at Z 15 the edge of the channel opened to the bulk.
  In some cases, astronomers can look along the axis of the dust torus from above or from below and have a clear view of the black hole.
  Cassini will cross the torus of dust in Enceladus' orbit and must turn to a protective attitude.
  Surrounding the pulsar is a bright doughnut-shaped, or toroidal, structure, with jet-like features extending in a perpendicular direction away from the torus.
2Architecture
A large convex moulding, typically semicircular in cross section, especially as the lowest part of the base of a column.
〔建筑〕环状半圆线脚装饰；柱脚圆盘线脚
Example sentencesExamples
- The gadrooned flattened torus moulding, shown on the shelf or footrest of the stand in the engraving also appears on the stretchers of the Blenheim stands.
- A long cylindrical bar of orange-painted steel evokes a tori (temple gate) and serves as a balustrade.
- One stand has a torus molding with red-painted triglyph and metopal sections, while a lower register has alternating black and white sections.
3Anatomy
A ridge of bone or muscle.
〔剖〕隆凸，圆枕
the maxillary torus
上颌隆凸。
Example sentencesExamples
- Other names are ‘occipital spur or torus occipitalis’, it is the insertion site of the ligamentum nuchae.
- In children, the most common injury is the torus fracture, which occurs with a fall onto an outstretched hand.
- A longitudinal ridge of the bony palate, torus palatinus, may be present in the region of the median palatine suture and extends laterally from it.
- The supraorbital torus is lost in most modern humans, and ridging above the orbits in general is very reduced.
- Also common is torus palatinus, a slow growing, asymptomatic, benign bony lump in the midline of the palate.
- There is no continuous torus; the very robust glabella and superciliary arches are well defined’.
- A torus, or ‘buckle,’ fracture of the distal radius is a common type of fracture in children.
4Botany
The receptacle of a flower.
〔植〕花托

Origin

Mid 16th century (in sense 2): from Latin, literally 'swelling, bolster, round moulding'. The other senses date from the 19th century.

Rhymes

brachiosaurus, brontosaurus, canorous, chorus, Epidaurus, giganotosaurus, Horus, megalosaurus, pelorus, porous, sorus, stegosaurus, Taurus, thesaurus, tyrannosaurus

Definition of torus in US English:

torus

nounˈtɔrəsˈtôrəs

1Geometry
A surface or solid formed by rotating a closed curve, especially a circle, around a line that lies in the same plane but does not intersect it (e.g., like a ring-shaped doughnut).
〔几何〕环形圆纹曲面，环面，锚环
Example sentencesExamples
- To avoid edge effects, the lattice is represented on a circle for a one-dimensional model or a torus for a two-dimensional model.
- ‘In other words, each solution could be drawn on the surface of a torus,’ he notes.
- To be rigorous, the hole is not actually in the torus: the torus is the surface and the hole is in the space around the surface.
- We can also represent the flat hexagonal torus as a tiling of flat space, as in fig.9.
- The surface of a sphere is a good example, as is a torus (the mathematical name for the shape of the surface of a quoit, or a ring-shaped doughnut).
- You can see a movie of a flat surface becoming a torus at this page about Paper Strip Activities.
- Into how many pieces can one cut a torus using two planes?
- Because the two periods are not related by an integer but are incommensurate, the system does not flow toward a closed path but instead orbits without converging on the surface of the torus.
- The surface area of the inside portion of a torus can be obtained by integrating Eq. 4, which yields
- A small patch of a sphere or torus surface looks almost like a piece of a flat plane and has area rather than volume.
- ‘And it stands to reason that they would have other toruses dotting the quadrant,’ Maria speculated.
- I found there that the solution of Archytus involves three surfaces - torus, cylinder, and cone.
- The resulting surface is a two-manifold called a torus.
- A bagel can serve as a physical model for a mathematical surface called a torus.
- ‘It appears the torus is rotating like a wheel,’ she continued.
- Intuitively, this is a consequence of the fact that two lineages can be functionally separated by a greater distance in a rectangle than in a torus.
- The Clifford torus is generated by a family of circles.
- In the formula of the curve given above the torus is formed from a circle of radius a whose centre is rotated along a circle of radius r.
- All the quasi-fuchsian subgroups correspond to pairs of once-punctured tori, but as one tends to the boundary a certain curve on one of the tori may get squeezed to a point.
- There are three classical attractors, a point which characterises a steady state system, a closed loop which characterises a periodic system, and a torus which combines several cycles.
1. 1.1 A thing of this shape, especially a large ring-shaped chamber used in physical research.
  环形物（尤指开展物理研究的大型环形室）
  Example sentencesExamples
  Nat Fisch of Princeton University and his colleagues propose driving the current by adding energy in only a small region, rather than everywhere around the torus.
  The floor curved more gradually along the torus, so that the rows of apple and plum trees seemed to rise up on the side of a rolling hill, above the top of the nearby hay, until they disappeared in the horizon defined by the artificial sunlight.
  The shuttle left the station at the same time that the invisible ship, the Sentinel, left their orbit for the torus.
  ‘He's good,’ Maria said as she angled the ship to orbit the torus.
  The downfield resonance is attributed to molecules (mostly DCPC) on the highly curved region of the bicelle torus.
  By carefully accounting for the particles injected into the machine and for those exhausted in the pumping system we found a deficit, indicating that a large fraction of deuterium gets trapped in the walls and components inside the torus.
  Hence the results presented for the torus will have general relevance for vestibular channels.
  It is possible that in this scan area the vesicles were not well dispersed; however, we cannot discount the possibility of irregular shapes being formed in addition to the torus and horseshoe shapes.
  Like tokamaks, their currently more advanced cousins, stellarators use magnetic fields to confine plasma in a torus for fusion reactions.
  When a neutron star binary coalesces, the rapidly spinning merged system is expected to form a spinning black hole, orbited momentarily by a torus of neutron-density matter.
  The Constitution fired one shot from a single turret, blasting a hole into one side of the torus that formed the bulk of the station.
  This remarkable device consists of a torus of alternating magnetic materials that are chosen so that the torus has a huge net spin - 10 22 aligned electron spins - yet produces no magnetic field.
  Mark wondered why the rotating torus wasn't crushed from the tremendous gravitational forces at the mouth of the wormhole.
  The innermost sections have the shape of a torus, but at Z 15 the edge of the channel opened to the bulk.
  The ships were built around a torus shaped Spacial-Warp core.
  Surrounding the pulsar is a bright doughnut-shaped, or toroidal, structure, with jet-like features extending in a perpendicular direction away from the torus.
  Cassini will cross the torus of dust in Enceladus' orbit and must turn to a protective attitude.
  A set of six hoop coils around the outside of the machine produces the magnetic field that shapes and positions the plasma centrally in the torus.
  In some cases, astronomers can look along the axis of the dust torus from above or from below and have a clear view of the black hole.
  The defense platform was a torus with three large solar panel arrays extending out from it with 120 degrees between them.
2Architecture
A large convex molding, typically semicircular in cross section, especially as the lowest part of the base of a column.
〔建筑〕环状半圆线脚装饰；柱脚圆盘线脚
Example sentencesExamples
- The gadrooned flattened torus moulding, shown on the shelf or footrest of the stand in the engraving also appears on the stretchers of the Blenheim stands.
- One stand has a torus molding with red-painted triglyph and metopal sections, while a lower register has alternating black and white sections.
- A long cylindrical bar of orange-painted steel evokes a tori (temple gate) and serves as a balustrade.
3Anatomy
A ridge of bone or muscle.
〔剖〕隆凸，圆枕
the maxillary torus
上颌隆凸。
Example sentencesExamples
- Other names are ‘occipital spur or torus occipitalis’, it is the insertion site of the ligamentum nuchae.
- A torus, or ‘buckle,’ fracture of the distal radius is a common type of fracture in children.
- A longitudinal ridge of the bony palate, torus palatinus, may be present in the region of the median palatine suture and extends laterally from it.
- In children, the most common injury is the torus fracture, which occurs with a fall onto an outstretched hand.
- There is no continuous torus; the very robust glabella and superciliary arches are well defined’.
- The supraorbital torus is lost in most modern humans, and ridging above the orbits in general is very reduced.
- Also common is torus palatinus, a slow growing, asymptomatic, benign bony lump in the midline of the palate.
4Botany
The receptacle of a flower.
〔植〕花托

Origin

Mid 16th century (in torus (sense 2)): from Latin, literally ‘swelling, bolster, round molding’. The other senses date from the 19th century.

单词	torus
释义	Definition of torus in English: torus nounPlural toruses, Plural tori ˈtɔːrəsˈtɔrəs 1Geometry A surface or solid formed by rotating a closed curve, especially a circle, about a line which lies in the same plane but does not intersect it (e.g. like a ring doughnut). 〔几何〕环形圆纹曲面，环面，锚环 Example sentencesExamples You can see a movie of a flat surface becoming a torus at this page about Paper Strip Activities. A small patch of a sphere or torus surface looks almost like a piece of a flat plane and has area rather than volume. ‘It appears the torus is rotating like a wheel,’ she continued. Into how many pieces can one cut a torus using two planes? ‘In other words, each solution could be drawn on the surface of a torus,’ he notes. To avoid edge effects, the lattice is represented on a circle for a one-dimensional model or a torus for a two-dimensional model. The resulting surface is a two-manifold called a torus. Because the two periods are not related by an integer but are incommensurate, the system does not flow toward a closed path but instead orbits without converging on the surface of the torus. A bagel can serve as a physical model for a mathematical surface called a torus. Intuitively, this is a consequence of the fact that two lineages can be functionally separated by a greater distance in a rectangle than in a torus. We can also represent the flat hexagonal torus as a tiling of flat space, as in fig.9. The surface of a sphere is a good example, as is a torus (the mathematical name for the shape of the surface of a quoit, or a ring-shaped doughnut). I found there that the solution of Archytus involves three surfaces - torus, cylinder, and cone. There are three classical attractors, a point which characterises a steady state system, a closed loop which characterises a periodic system, and a torus which combines several cycles. The surface area of the inside portion of a torus can be obtained by integrating Eq. 4, which yields The Clifford torus is generated by a family of circles. ‘And it stands to reason that they would have other toruses dotting the quadrant,’ Maria speculated. To be rigorous, the hole is not actually in the torus: the torus is the surface and the hole is in the space around the surface. In the formula of the curve given above the torus is formed from a circle of radius a whose centre is rotated along a circle of radius r. All the quasi-fuchsian subgroups correspond to pairs of once-punctured tori, but as one tends to the boundary a certain curve on one of the tori may get squeezed to a point. 1.1 A ring-shaped object, especially a large ring-shaped chamber used in physical research. 环形物（尤指开展物理研究的大型环形室） Example sentencesExamples The downfield resonance is attributed to molecules (mostly DCPC) on the highly curved region of the bicelle torus. A set of six hoop coils around the outside of the machine produces the magnetic field that shapes and positions the plasma centrally in the torus. The defense platform was a torus with three large solar panel arrays extending out from it with 120 degrees between them. When a neutron star binary coalesces, the rapidly spinning merged system is expected to form a spinning black hole, orbited momentarily by a torus of neutron-density matter. ‘He's good,’ Maria said as she angled the ship to orbit the torus. It is possible that in this scan area the vesicles were not well dispersed; however, we cannot discount the possibility of irregular shapes being formed in addition to the torus and horseshoe shapes. Nat Fisch of Princeton University and his colleagues propose driving the current by adding energy in only a small region, rather than everywhere around the torus. Hence the results presented for the torus will have general relevance for vestibular channels. Mark wondered why the rotating torus wasn't crushed from the tremendous gravitational forces at the mouth of the wormhole. Like tokamaks, their currently more advanced cousins, stellarators use magnetic fields to confine plasma in a torus for fusion reactions. The shuttle left the station at the same time that the invisible ship, the Sentinel, left their orbit for the torus. The ships were built around a torus shaped Spacial-Warp core. By carefully accounting for the particles injected into the machine and for those exhausted in the pumping system we found a deficit, indicating that a large fraction of deuterium gets trapped in the walls and components inside the torus. The floor curved more gradually along the torus, so that the rows of apple and plum trees seemed to rise up on the side of a rolling hill, above the top of the nearby hay, until they disappeared in the horizon defined by the artificial sunlight. The Constitution fired one shot from a single turret, blasting a hole into one side of the torus that formed the bulk of the station. This remarkable device consists of a torus of alternating magnetic materials that are chosen so that the torus has a huge net spin - 10 22 aligned electron spins - yet produces no magnetic field. The innermost sections have the shape of a torus, but at Z 15 the edge of the channel opened to the bulk. In some cases, astronomers can look along the axis of the dust torus from above or from below and have a clear view of the black hole. Cassini will cross the torus of dust in Enceladus' orbit and must turn to a protective attitude. Surrounding the pulsar is a bright doughnut-shaped, or toroidal, structure, with jet-like features extending in a perpendicular direction away from the torus. 2Architecture A large convex moulding, typically semicircular in cross section, especially as the lowest part of the base of a column. 〔建筑〕环状半圆线脚装饰；柱脚圆盘线脚 Example sentencesExamples The gadrooned flattened torus moulding, shown on the shelf or footrest of the stand in the engraving also appears on the stretchers of the Blenheim stands. A long cylindrical bar of orange-painted steel evokes a tori (temple gate) and serves as a balustrade. One stand has a torus molding with red-painted triglyph and metopal sections, while a lower register has alternating black and white sections. 3Anatomy A ridge of bone or muscle. 〔剖〕隆凸，圆枕 the maxillary torus 上颌隆凸。 Example sentencesExamples Other names are ‘occipital spur or torus occipitalis’, it is the insertion site of the ligamentum nuchae. In children, the most common injury is the torus fracture, which occurs with a fall onto an outstretched hand. A longitudinal ridge of the bony palate, torus palatinus, may be present in the region of the median palatine suture and extends laterally from it. The supraorbital torus is lost in most modern humans, and ridging above the orbits in general is very reduced. Also common is torus palatinus, a slow growing, asymptomatic, benign bony lump in the midline of the palate. There is no continuous torus; the very robust glabella and superciliary arches are well defined’. A torus, or ‘buckle,’ fracture of the distal radius is a common type of fracture in children. 4Botany The receptacle of a flower. 〔植〕花托 Origin Mid 16th century (in sense 2): from Latin, literally 'swelling, bolster, round moulding'. The other senses date from the 19th century. Rhymes brachiosaurus, brontosaurus, canorous, chorus, Epidaurus, giganotosaurus, Horus, megalosaurus, pelorus, porous, sorus, stegosaurus, Taurus, thesaurus, tyrannosaurus Definition of torus in US English: torus nounˈtɔrəsˈtôrəs 1Geometry A surface or solid formed by rotating a closed curve, especially a circle, around a line that lies in the same plane but does not intersect it (e.g., like a ring-shaped doughnut). 〔几何〕环形圆纹曲面，环面，锚环 Example sentencesExamples To avoid edge effects, the lattice is represented on a circle for a one-dimensional model or a torus for a two-dimensional model. ‘In other words, each solution could be drawn on the surface of a torus,’ he notes. To be rigorous, the hole is not actually in the torus: the torus is the surface and the hole is in the space around the surface. We can also represent the flat hexagonal torus as a tiling of flat space, as in fig.9. The surface of a sphere is a good example, as is a torus (the mathematical name for the shape of the surface of a quoit, or a ring-shaped doughnut). You can see a movie of a flat surface becoming a torus at this page about Paper Strip Activities. Into how many pieces can one cut a torus using two planes? Because the two periods are not related by an integer but are incommensurate, the system does not flow toward a closed path but instead orbits without converging on the surface of the torus. The surface area of the inside portion of a torus can be obtained by integrating Eq. 4, which yields A small patch of a sphere or torus surface looks almost like a piece of a flat plane and has area rather than volume. ‘And it stands to reason that they would have other toruses dotting the quadrant,’ Maria speculated. I found there that the solution of Archytus involves three surfaces - torus, cylinder, and cone. The resulting surface is a two-manifold called a torus. A bagel can serve as a physical model for a mathematical surface called a torus. ‘It appears the torus is rotating like a wheel,’ she continued. Intuitively, this is a consequence of the fact that two lineages can be functionally separated by a greater distance in a rectangle than in a torus. The Clifford torus is generated by a family of circles. In the formula of the curve given above the torus is formed from a circle of radius a whose centre is rotated along a circle of radius r. All the quasi-fuchsian subgroups correspond to pairs of once-punctured tori, but as one tends to the boundary a certain curve on one of the tori may get squeezed to a point. There are three classical attractors, a point which characterises a steady state system, a closed loop which characterises a periodic system, and a torus which combines several cycles. 1.1 A thing of this shape, especially a large ring-shaped chamber used in physical research. 环形物（尤指开展物理研究的大型环形室） Example sentencesExamples Nat Fisch of Princeton University and his colleagues propose driving the current by adding energy in only a small region, rather than everywhere around the torus. The floor curved more gradually along the torus, so that the rows of apple and plum trees seemed to rise up on the side of a rolling hill, above the top of the nearby hay, until they disappeared in the horizon defined by the artificial sunlight. The shuttle left the station at the same time that the invisible ship, the Sentinel, left their orbit for the torus. ‘He's good,’ Maria said as she angled the ship to orbit the torus. The downfield resonance is attributed to molecules (mostly DCPC) on the highly curved region of the bicelle torus. By carefully accounting for the particles injected into the machine and for those exhausted in the pumping system we found a deficit, indicating that a large fraction of deuterium gets trapped in the walls and components inside the torus. Hence the results presented for the torus will have general relevance for vestibular channels. It is possible that in this scan area the vesicles were not well dispersed; however, we cannot discount the possibility of irregular shapes being formed in addition to the torus and horseshoe shapes. Like tokamaks, their currently more advanced cousins, stellarators use magnetic fields to confine plasma in a torus for fusion reactions. When a neutron star binary coalesces, the rapidly spinning merged system is expected to form a spinning black hole, orbited momentarily by a torus of neutron-density matter. The Constitution fired one shot from a single turret, blasting a hole into one side of the torus that formed the bulk of the station. This remarkable device consists of a torus of alternating magnetic materials that are chosen so that the torus has a huge net spin - 10 22 aligned electron spins - yet produces no magnetic field. Mark wondered why the rotating torus wasn't crushed from the tremendous gravitational forces at the mouth of the wormhole. The innermost sections have the shape of a torus, but at Z 15 the edge of the channel opened to the bulk. The ships were built around a torus shaped Spacial-Warp core. Surrounding the pulsar is a bright doughnut-shaped, or toroidal, structure, with jet-like features extending in a perpendicular direction away from the torus. Cassini will cross the torus of dust in Enceladus' orbit and must turn to a protective attitude. A set of six hoop coils around the outside of the machine produces the magnetic field that shapes and positions the plasma centrally in the torus. In some cases, astronomers can look along the axis of the dust torus from above or from below and have a clear view of the black hole. The defense platform was a torus with three large solar panel arrays extending out from it with 120 degrees between them. 2Architecture A large convex molding, typically semicircular in cross section, especially as the lowest part of the base of a column. 〔建筑〕环状半圆线脚装饰；柱脚圆盘线脚 Example sentencesExamples The gadrooned flattened torus moulding, shown on the shelf or footrest of the stand in the engraving also appears on the stretchers of the Blenheim stands. One stand has a torus molding with red-painted triglyph and metopal sections, while a lower register has alternating black and white sections. A long cylindrical bar of orange-painted steel evokes a tori (temple gate) and serves as a balustrade. 3Anatomy A ridge of bone or muscle. 〔剖〕隆凸，圆枕 the maxillary torus 上颌隆凸。 Example sentencesExamples Other names are ‘occipital spur or torus occipitalis’, it is the insertion site of the ligamentum nuchae. A torus, or ‘buckle,’ fracture of the distal radius is a common type of fracture in children. A longitudinal ridge of the bony palate, torus palatinus, may be present in the region of the median palatine suture and extends laterally from it. In children, the most common injury is the torus fracture, which occurs with a fall onto an outstretched hand. There is no continuous torus; the very robust glabella and superciliary arches are well defined’. The supraorbital torus is lost in most modern humans, and ridging above the orbits in general is very reduced. Also common is torus palatinus, a slow growing, asymptomatic, benign bony lump in the midline of the palate. 4Botany The receptacle of a flower. 〔植〕花托 Origin Mid 16th century (in torus (sense 2)): from Latin, literally ‘swelling, bolster, round molding’. The other senses date from the 19th century.
随便看	isolations isolation tank isolation ward isolative isolator isolator isolators Isolde isoleucine isoleucines isoline i-som isomer isomerase isomerases isomeric isomeric isomerically isomerisation isomerisations isomerise isomerism isomerism isomerisms isomerization