The measurement of the optic axial angle of minerals in the thin section

In nearly every thin section of a rock containing monoelinic pyroxenes it will be found that one or more crystals twinned on the orthopinacoid (100) are included. In such crystals the twin-plane is marked very clearly by the difference of relative retardation and extinction, and also by the interference-bands if the twin-plane is inclined to the plane of section. For the purposes of the complete optical determination, it is essential for the proposed method that one half of the twin should exhibit the emergence of an optic axis suitable for the determination of the optic axial angle by the Becke method.

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Note on the determination of the optic axial angle of a crystal in thin-section by the Mallard-Becke method

Mineralogical Magazine and Journal of the Mineralogical Society ◽

10.1180/minmag.1913.016.77.08 ◽

1913 ◽

Vol 16 (77) ◽

pp. 348-351 ◽

Cited By ~ 1

Author(s):

Harvey Collingridge

Keyword(s):

Thin Section ◽

Stereographic Projection ◽

Original Method ◽

Graphic Method ◽

Camera Lucida ◽

Axial Angle ◽

Linear Distance

Mallard's original method was based on the measurement of the linear distance, as determined by an eyepiece-micrometer, between the optic axes in a section of the crystal at right angles to the acute biseetrix viewed in convergent light.Professor F. Becke implored on this method by utilizing sections which were not at right angles to the acute hissetrix, but in which both optic axes were visible in the field. He projected both axes by means of an Abbe camera lucida on to a revolving drawing-table, and by means of the Mallard equation plotted the axes on a stereographic projection and thus obtained the optic axial angle, the angles of course being corrected for refraction to the true angles in the crystal section. Professor Becke subsequently, by utilizing the Biot-Fresnel law, formulated a graphic method of obtaining the optic axial angle from a section in which only one axis was visible.

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A Monticellite-Nepheline-Basalt from Tasmania: a correction to mineral data

Geological Magazine ◽

10.1017/s0016756800102572 ◽

1928 ◽

Vol 65 (1) ◽

pp. 29-30 ◽

Cited By ~ 2

Author(s):

C. E. Tilley

Keyword(s):

Optical Properties ◽

Thin Section ◽

Late Stage ◽

Present Note ◽

Close Correspondence ◽

Axial Angle ◽

History Of ◽

Mineral Data

F. P. Paul described in 1906 (T.M.P.M., vol. 25, p. 309) a nepheline-eudialite-basalt from Shannon Tier, Tasmania, containing an unknown mineral referred by him to Ca2SiO4. Subsequently Bowen (Amer. J. Sci., 1922, p. 30) pointed out the close correspondence between the optical properties of Paul's mineral and of the artificial βCa2SiO4 prepared by Day, Shepherd and Wright. Still later (Geol. Mag., 1927, p. 43) the writer of this note ventured to apply the name shannonite to the mineral of this singular occurrence. Since that time through the kindness of Mr. P. B. Nye, Government Geologist of Tasmania, a specimen of the rock described by Paul from Shannon Tier has been obtained and examined. That the specimen examined is identical with the rock described by Paul is clearly indicated by his detailed description and the photomicrograph which accompanies his paper. Unfortunately my own determinations are not in agreement with those of Paul, and the purpose of the present note isto state the nature of these discrepancies. The rock is a felspar-free nepheline-basalt of which the chief constituents are idiomorphic nepheline, a titaniferous augite, olivine (chrysolite), the unknown mineral of Paul, biotite, apatite, magnetite, perofskite, and minor amounts of interstitial analcime. The described eudialite has not been discovered, and from the description attached to the photomicrograph this mineral appears to have been confused with nepheline. I find further that the properties of the unknown mineral agree, not with those of any of the artificial calcium orthosilicates, but with those of monticellite. The two olivines are readily distinguished in thin section, the chrysolite occurring as chadacrysts and the monticellite as oikocrysts, the latter appearing as shapeless grains often surrounding chrysolite and enclosing numerous idiomorphic crystals of nepheline and magnetite, and thus belonging to a late stage in the crystallization history of the rock. The chrysolite moreover is readily distinguished—apart from these textural differences—by its higher birefringence and larger optic axial angle (near 90°).

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The Infection of Cells by Bullet-Shaped Viruses

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100063779 ◽

1969 ◽

Vol 27 ◽

pp. 372-373

Author(s):

Frederick A. Murphy ◽

Alyne K. Harrison ◽

Sylvia G. Whitfield

Keyword(s):

Electron Microscopy ◽

Physical Properties ◽

Host Cell ◽

Thin Section ◽

Cultured Cells ◽

Cell Infection ◽

Thin Section Electron Microscopy ◽

Section Electron ◽

Section Electron Microscopy

The bullet-shaped viruses are currently classified together on the basis of similarities in virion morphology and physical properties. Biologically and ecologically the member viruses are extremely diverse. In searching for further bases for making comparisons of these agents, the nature of host cell infection, both in vivo and in cultured cells, has been explored by thin-section electron microscopy.

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Deformation of Yeast Plasma Membrane by Ethidium Bromide

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100103334 ◽

1988 ◽

Vol 46 ◽

pp. 254-255

Author(s):

E. Keyhani

Keyword(s):

Plasma Membrane ◽

Thin Section ◽

Ethidium Bromide ◽

Freeze Fracture ◽

Mutagenic Effect ◽

Yeast Cells ◽

Hydrophobic Region ◽

Thin Section Electron Microscopy ◽

Section Electron ◽

Deep Pits

The mutagenic effect of ethidium bromide on the mitochondrial DNA is well established. Using thin section electron microscopy, it was shown that when yeast cells were grown in the presence of ethidium bromide, besides alterations in the mitochondria, the plasma membrane also showed alterations consisting of 75 to 110 nm-deep pits. Furthermore, ethidium bromide induced an increase in the length and number of endoplasmic reticulum and in the number of intracytoplasmic vesicles.Freeze-fracture, by splitting the hydrophobic region of the membrane, allows the visualization of the surface view of the membrane, and consequently, any alteration induced by ethidium bromide on the membrane can be better examined by this method than by the thin section method.Yeast cells, Candida utilis. were grown in the presence of 35 μM ethidium bromide. Cells were harvested and freeze-fractured according to the procedure previously described.

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The Mechanomorphology of Microtubule Sliding

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s143192760000266x ◽

1980 ◽

Vol 38 ◽

pp. 604-607

Author(s):

P. Satir ◽

J. Wais-Steder ◽

J. Avolio

Keyword(s):

Thin Section ◽

Dynein Arms

In 1977, Sale and Satir showed that active microtubule sliding in trypsin-treated Tetrahymena axonemes is always of a single polarity. If the doublet bearing active arms is labelled N, by convention, the doublet that is pushed by those arms is N+l. In active sliding in trypsin-treated axonemes doublet N+l is always displaced tipwards with respect to N. Several different configurations of the dynein arms have been described. These include: (1) an extended configuration, where the dynein arms are tilted about 40° towards the base of the axoneme and are long enough to span the space between doublets N and Ntl completely (2) a standard, unattached image, such as is usually seen in thin section. In this configuration, the arms do not span the interdoublet gap. (3) the rigor image, where the arms always bridge the gap. This differs from the extended configuration because tilt is often absent, so that the arms often lie normal to doublets N and N+l.

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