The determination of the maximum extinction-angle, optic axial angle, and birefringence in twinned crystals of monoclinic pyroxenes in thin section by the Becke method

1914 ◽  
Vol 17 (80) ◽  
pp. 147-149
Author(s):  
Harvey Collingridge
Keyword(s):  
Thin Section ◽  
Twin Plane ◽  
Optic Axis ◽  
Axial Angle ◽  
Extinction Angle ◽  
Optical Determination ◽  
The Difference ◽  
Relative Retardation

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.

New techniques for the universal stage. II. The determination of the 2V when only one optic axis is accessible

1958 ◽  
Vol 31 (241) ◽  
pp. 878-882 ◽  
Author(s):  
N. Joel ◽  
I. D. Muir
Keyword(s):  
Normal Incidence ◽  
Optic Axis ◽  
Sufficient Accuracy ◽  
Stage Ii ◽  
Biaxial Crystal ◽  
New Techniques ◽  
Axial Angle ◽  
Universal Stage

SummaryWhen one optic axis of a biaxial crystal has been located accurately by the usual orthoseopic or conoscopic methods, the second may be located by determining the extinction positions at normal incidence and applying the Biot-Fresnel construction. When use is made of the extinction directions associated with two or more wave normals inclined to the section, this method gives more reliable values of the optic axial angle than can be obtained by the doubling of the angle V over the pole of a bisectrix. If the optic axes have been located with sufficient accuracy by this procedure, then this also determines the orientation of the indicatrix.

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

1913 ◽  
Vol 16 (77) ◽  
pp. 348-351 ◽  
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.

Determination of optic axial orientation of uniaxial minerals and of dolomite using an ordinary microscope

1968 ◽  
Vol 5 (5) ◽  
pp. 1323-1329 ◽  
Author(s):  
C. S. Venkitasubramanyan
Keyword(s):  
Thin Section ◽  
Twin Plane ◽  
Axial Orientation ◽  
Twin Lamella ◽  
Reference Position

Schumann's method for determination of the orientation of the C-axis of uniaxial minerals using an ordinary petrographic microscope, described nearly thirty years ago, apparently has been generally overlooked in this country. It is simple, faster, and in certain cases more accurate than determinations using a universal stage.As an additional determination, since in dolomite the pole to the twin plane [Formula: see text] lies at [Formula: see text] to the C-axis, the orientation of the twin plane can be found if the attitude of the C-axis and the 'strike' of the twin lamella when the thin section is in a reference position are known. The method is not successful with calcite because [Formula: see text] is only 26°, leading to ambiguous answers for most orientations.

Determination of the optic axial angle of biaxial crystals in parallel polarized light

1906 ◽  
Vol 14 (65) ◽  
pp. 157-159
Author(s):  
John W. Evans
Keyword(s):  
Refractive Index ◽  
Polarized Light ◽  
Optic Axis ◽  
Original Position ◽  
Axial Angle ◽  
Axis Of Rotation ◽  
Axis Parallel ◽  
Made In ◽  
The Revolution

It will in the first place be assumed for the sake of simplicity that the crystal to be investigated is immersed in a liquid having a refractive index as nearly as possible equal to the intermediate refractive index (β), so that light travelling along the optic axis t is not appreciably refracted on entering or leaving the crystal.The observation is made in parallel ight between crossed nicols, which are rotated together till a position of extinction is reached, when the directions of vibration of the nicols wilI be parallel to those in the crystal. If the latter be now rotated on an axis parallel to one of these directions, it will in general show light throughout the revolution, except in the original position and that opposite to it. Occasionally, however, it will remain dark throughout; in that case the axis of rotation is the bisectrix of an optic axial angle.

Optical determination of aegirine-augite with the universal stage

1962 ◽  
Vol 33 (257) ◽  
pp. 132-137 ◽  
Author(s):  
Basil C. King
Keyword(s):  
Accurate Determination ◽  
Optic Axis ◽  
Strong Absorption ◽  
Alternative Procedure ◽  
Optical Determination ◽  
The One ◽  
Absorption And Dispersion ◽  
Universal Stage

SummaryThe accurate determination of α:[001] and 2V in members of the aegirine-augite series often presents difficulties owing to strong absorption and dispersion, especially as high angles of tilt on the universal stage are often involved. Both of these angles depend on the location of α, and this operation is the one most subject to error.An alternative procedure is the determination of A:[001], the angle between an optic axis and [001]. This angle is very easily and accurately determined and varies systematically with composition. It can be derived from the values for α:[001] and 2V, while conversely values of α:[001] and 2V can be obtained from A:[001] by reference to standard curves.

Extinction curves and 2V: a stereographic solution

1962 ◽  
Vol 33 (256) ◽  
pp. 52-58 ◽  
Author(s):  
F. E. Tocher
Keyword(s):  
Optic Axis ◽  
Biaxial Crystal ◽  
Graphical Approach ◽  
Axial Angle ◽  
True Position ◽  
Method Show

Summary Utilizing the Biot-Fresnel construction in reverse, the magnitude and sign of the optic axial angle of a biaxial crystal are determinable from the stereogram of the extinction curves. Refinements in the determination of the extinction curves include the use of conoscopic observations, and of crystal cylinders instead of irregular fragments or entire crystals. Direct 2V measurements on some of the material investigated by this method show that this indirect and graphical approach permits the location of each optic axis to within ¼° of its true position.

On the determination of the optic axial angle and crystal-forms from observations by the Becke method in thin sections

1928 ◽  
Vol 21 (122) ◽  
pp. 552-555
Author(s):  
Harvey Collingridge
Keyword(s):  
Optical System ◽  
Optic Axis ◽  
Axial Plane ◽  
Thin Sections ◽  
Crystal Forms ◽  
Axial Angle ◽  
Exact Position

Some years ago the writer read a paper on the determination of the optic axial angle of a crystal by the Becke method. This proposed method was to record the trace of the optic axial plane when horizontal, the position of one axis, and the extinction-direction. From these data and the established constants of the microscope, the position of the second optic axis may be found, as the extinction bisects the angle between the centre of the pole of the section and the two optic axes. Hence, the optic axial angle may be determined.Considerable errors arise in these determinations owing to defects in the optical system of the microscope, and also to the inability to determine the exact position when the trace of the optic axial plane is parallel to the E-W. lines in the microscope.

FRACTIONAL DETERMINATIONS OF URINARY 17-KETOSTEROIDS IN HYPEREMESIS GRAVIDARUM

1962 ◽  
Vol 41 (1) ◽  
pp. 123-128 ◽  
Author(s):  
Pentti A. Järvinen ◽  
Sykkö Pesonen ◽  
Pirkko Väänänen
Keyword(s):  
Hyperemesis Gravidarum ◽  
First Trimester ◽  
Control Group ◽  
Before And After ◽  
Daily Urine ◽  
First Trimester Of Pregnancy ◽  
The Difference

ABSTRACT The fractional determination of 17-ketosteroids in the daily urine was performed in nine cases of hyperemesis gravidarum and in four control cases, in the first trimester of pregnancy both before and after corticotrophin administration. The excretion of total 17-KS is similar in the two groups. Only in the hyperemesis group does the excretion of total 17-KS increase significantly after corticotrophin administration. The fractional determination reveals no difference between the two groups of patients with regard to the values of the fractions U (unidentified 17-KS), A (androsterone) and Rest (11-oxygenated 17-KS). The excretion of dehydroepiandrosterone is significantly higher in the hyperemesis group than in the control group. The excretion of androstanolone seems to be lower in the hyperemesis group than in the control group, but the difference is not statistically significant. The differences in the correlation between dehydroepiandrosterone and androstanolone in the two groups is significant. The high excretion of dehydroepiandrosterone and low excretion of androstanolone in cases of hyperemesis gravidarum is a sign of adrenal dysfunction.

THE SUBJECT FIELD OF INSTITUTIONAL EDUCATION: THE SENSE AND PROSPECTS OF DEVELOPMENT IN UKRAINE

2020 ◽  
pp. 25-38
Author(s):  
Irina Mordous
Keyword(s):  
Decisive Role ◽  
Subject Field ◽  
National Education ◽  
Progressive Development ◽  
Separate Area ◽  
Economic Transformations ◽  
The Difference ◽  
The Individual ◽  
Political Economic

The development of modern civilization attests to its decisive role in the progressive development of institutions. They identified the difference between Western civilization and the rest of the world. Confirmation of the institutional advantages of the West was its early industrialization. The genesis and formation of institutionalism in its ideological and conceptualmethodological orientation occurs as a process alternative to neoclassic in the context of world heterodoxia, which quickly spread in social science. Highlighting institutional education as a separate area of sociocultural activity is determined by the factor of differentiation of institutional theory as a whole. A feature of institutional education is its orientation toward the individual and his/her transformation into a personality. The content of institutional education is revealed through the analysis of the institution, which includes a set of established customs, traditions, ways of thinking, behavioral stereotypes of individuals and social groups. The dynamics of socio-political, economic transformations in Ukraine requires a review of the foundations of national education and determination of the prospects for its development in the 21st century in the context of institutionalism.

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