The Optic Angle in Relation to Strabismus

1934 ◽  
Vol 17 (4) ◽  
pp. 291-296
Author(s):  
E.L. Armstrong
Keyword(s):  
Optic Angle

Channel reduction schemes for fiber-optic angle encoders

1988 ◽  
Vol 7 (2) ◽  
pp. 115-137 ◽  
Author(s):  
J. T. Newmaster ◽  
M. R. Brininstool ◽  
T. Hofler ◽  
S. L. Garrett
Keyword(s):  
Fiber Optic ◽  
Channel Reduction ◽  
Optic Angle

The Role of Microscopy in the Study of Chemical Polymorphism

2000 ◽  
Vol 6 (S2) ◽  
pp. 1000-1001
Author(s):  
R.A. Carlton
Keyword(s):  
Solid State ◽  
Development Process ◽  
Polarized Light ◽  
Crystal Form ◽  
Chemical Polymorphism ◽  
Optic Angle ◽  
Temperature And Pressure ◽  
Metastable Forms ◽  
The Relationship

Chemical polymorphism refers to the ability of compounds to exist in different solid state forms. In general, these differ solely in their arrangement in space (i.e., their crystal form). Polymorphs typically have different solid state properties such as melting point, solubility, density, etc. They also commonly exhibit distinctive optical properties such as refractive index, extinction position, optic sign and optic angle. The choice of polymorph can be an important consideration in the drug development process if the solid state properties have wide differences. Further, it is generally desirable to develop the polymorph which is stable at room temperature and pressure, since metastable forms convert spontaneously to the stable ones, albeit often at a very slow rate. Optical, thermal and scanning electron microscopy each play important roles in the study of chemical polymorphism.Optical microscopy, and more specifically polarized light microscopy, contributes both to the discovery of new polymorphs and to the elucidation of the relationship among polymorphs.

scholarly journals Spicule Form in Leucosolenia complicata

1954 ◽  
Vol s3-95 (30) ◽  
pp. 191-203
Author(s):  
WALTER CLIFFORD JONES
Keyword(s):  
Optic Axis ◽  
Side View ◽  
Surface View ◽  
Separate Genus ◽  
Planar Angle ◽  
Optic Angle ◽  
Transverse View

The tri- and quadriradiates of Leucosolenia complicata are described in four aspects: surface view, transverse view, side view, and planar view. The spicule form and size vary with the distance from the oscular edge in all four cases. In planar view (when the eye is directed along the optic axis) the spicule rays usually appear straight and thus exhibit a tendency to grow in planes which intersect in a line having the direction of the optic axis. The angle between the oscular ray planes (the planar angle) is always greater than 120° and the spicules hence belong to the ‘secondary sagittal’ class of von Ebner. The planar angle is not closely correlated with the optic angle and varies from about 160° at the oscular edge to about 1400 at the base of the tube. This variation precludes the possibility that the angle is simply controlled by the crystallizing properties of calcite. The curvature of the choanoderm is a factor controlling spicule form because the formative calcoblasts move in contact with this layer when secreting their respective rays. Reasons are given for returning L. coriacea (Montagu) to a separate genus, Clathrina.

A new, sensitive diffractive optic angle meter

2002 ◽  
Author(s):  
Anders Magnusson ◽  
Kamyar Kazemi Moud ◽  
Sverker Hård
Keyword(s):  
Diffractive Optic ◽  
Optic Angle

Vigezzite, (Ca, Ce) (Nb, Ta,Ti)2O6, a new aeschynite-type mineral from the Alps

1979 ◽  
Vol 43 (328) ◽  
pp. 459-462 ◽  
Author(s):  
S. Graeser ◽  
H. Schwander ◽  
H. Hänni ◽  
V. Mattioli
Keyword(s):  
Vickers Hardness ◽  
Electron Microprobe ◽  
Northern Italy ◽  
New Mineral ◽  
Yellow Colour ◽  
X Ray ◽  
Orange Yellow ◽  
New Mineral Species ◽  
The Alps ◽  
Optic Angle

SummaryA new mineral species, vigezzite (Ca,Ce) (Nb,Ta,Ti)2O6, was found near Orcesco, Valle Vigezzo, Prov. Novara, Northern Italy. It forms fiat prismatic crystals up to 2–3 mm length of an orange-yellow colour. The crystals are elongated along the a-axis and flattened on (010). Cleavage at right angles to the prism axis is distinct, fracture conchoidal. Vickers hardness VHN = 396 kp/mm2, corresponding to -5 in the Mohs scale. Refraction indices are high: α = 2.14, γ = 2.315 (NaD, 589 µm), birefringence is 0.175. Optic angle 2Vγ is large. Though intensively yellow coloured, the mineral shows no pleochroism. α = c, β = b, γ = a; optic axial plane is parallel to (010).Vigezzite is orthorhombie with space group Pmnb or P21nb; a = 7.559±0.01, b = 11.028±0.01, c = 5.360± 0.004 Å, Z = 4. The six strongest lines of the X-ray powder pattern are 4.821 (9) (011), 3.784 (8) (200), 3.036 (10) (031), 2.974 (10) (211), 1.7129 (6) (242), 1.6018 (7) (431).Electron microprobe analyses lead to the empirical formula (Ca0.82Ce0.24)Σ1.06(Nb0.9Ta0.62Ti0.5)Σ2.02O6. The mineral is not completely homogenous, the ratio Nb/(Nb+Ta) varies from 0.55–0.62. Rynersonite Ca (Ta,Nb)2O6, may represent the Ta-dominant equivalent of vigezzite. Vigezzite occurs together with several other Nb-minerals such as pyrochlore, columbite and fersmite, whose crystallographical and chemical data are reported, in an albitic rock of presumably pegmatitic origin.

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