155. An electron microscopic and x-ray photoelectron spectroscopic study of calcined and partially gasified nickel containing chars

Direct electron microscopic study of biological molecules has been hampered by such factors as radiation damage, lack of contrast and vacuum drying. In certain cases, however, the difficulties may be overcome by using redundent structural information from repeating units and by various specimen preservation methods. With bilayers of phospholipids in which both the solid and fluid phases co-exist, the ordering of the hydrocarbon chains may be utilized to form diffraction contrast images. Domains of different molecular packings may be recgnizable by placing properly chosen filters in the diffraction plane. These domains would correspond to those observed by freeze fracture, if certain distinctive undulating patterns are associated with certain molecular packing, as suggested by X-ray diffraction studies. By using an environmental stage, we were able to directly observe these domains in bilayers of mixed phospholipids at various temperatures at which their phases change from misible to inmissible states.

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Polarity Determination in Sphalerite and Wurtzite Structures

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100136106 ◽

1990 ◽

Vol 48 (2) ◽

pp. 500-501

Author(s):

Stuart McKernan ◽

C. Barry Carter

Keyword(s):

Opposite Polarity ◽

Single Domain ◽

Polar Material ◽

Electron Microscopic ◽

Dynamical Interaction ◽

X Ray ◽

Polarity Determination ◽

The Absolute ◽

Microscopic Techniques

The determination of the absolute polarity of a polar material is often crucial to the understanding of the defects which occur in such materials. Several methods exist by which this determination may be performed. In bulk, single-domain specimens, macroscopic techniques may be used, such as the different etching behavior, using the appropriate etchant, of surfaces with opposite polarity. X-ray measurements under conditions where Friedel’s law (which means that the intensity of reflections from planes of opposite polarity are indistinguishable) breaks down can also be used to determine the absolute polarity of bulk, single-domain specimens. On the microscopic scale, and particularly where antiphase boundaries (APBs), which separate regions of opposite polarity exist, electron microscopic techniques must be employed. Two techniques are commonly practised; the first [1], involves the dynamical interaction of hoLz lines which interfere constructively or destructively with the zero order reflection, depending on the crystal polarity. The crystal polarity can therefore be directly deduced from the relative intensity of these interactions.

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X-Ray Microanalysis of Nickel and Cobalt Intensified Peroxidase- Antiperoxidase For Verification of Reaction Sites

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100119168 ◽

1985 ◽

Vol 43 ◽

pp. 468-469

Author(s):

A. Angel ◽

K. Miller ◽

V. Seybold ◽

R. Kriebel

Keyword(s):

Reaction Mechanisms ◽

Visual Discrimination ◽

Osmium Tetroxide ◽

Ultrastructural Level ◽

Microscopic Level ◽

Electron Microscopic Level ◽

Electron Microscopic ◽

X Ray ◽

Insoluble Polymer ◽

Cytochemical Reaction

Localization of specific substances at the ultrastructural level is dependent on the introduction of chemicals which will complex and impart an electron density at specific reaction sites. Peroxidase-antiperoxidase(PAP) methods have been successfully applied at the electron microscopic level. The PAP complex is localized by addition of its substrate, hydrogen peroxide and an electron donor, usually diaminobenzidine(DAB). On oxidation, DAB forms an insoluble polymer which is able to chelate with osmium tetroxide becoming electron dense. Since verification of reactivity is visual, discrimination of reaction product from osmiophillic structures may be difficult. Recently, x-ray microanalysis has been applied to examine cytochemical reaction precipitates, their distribution in tissues, and to study cytochemical reaction mechanisms. For example, immunoreactive sites labelled with gold have been ascertained by means of x-ray microanalysis.

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Factors in Photographic Emulsions for Low Dose Electron Crystallography

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s143192760000101x ◽

1980 ◽

Vol 38 ◽

pp. 230-231

Author(s):

T.W. Jeng ◽

W. Chiu

Keyword(s):

Radiation Damage ◽

Low Dose ◽

Damage Effect ◽

Photographic Emulsion ◽

Electron Crystallography ◽

Electron Microscopic ◽

X Ray ◽

Signal Contrast ◽

Diffraction Patterns ◽

Photographic Emulsions

With the advances in preparing biological materials in a thin and highly ordered form, and in maintaining them hydrated under vacuum, electron crystallography has become an important tool for biological structure investigation at high resolution (1,2). However, the electron radiation damage would limit the capability of recording reflections with low intensities in an electron diffraction pattern. It has been demonstrated that the use of a low temperature stage can reduce the radiation damage effect and that one can expose the specimen with a higher dose in order to increase the signal contrast (3). A further improvement can be made by selecting a proper photographic emulsion. The primary factors in evaluating the suitability of photographic emulsion for recording low dose diffraction patterns are speed, fog level, electron response at low electron exposure, linearity, and usable range of exposure. We have compared these factors with three photographic emulsions including Kodak electron microscopic plate (EMP), Industrex AA x-ray film (AA x-ray) and Kodak nuclear track film (NTB3).

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Infrared spectroscopic study of the YPO4-YCrO4 system

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19852139 ◽

1985 ◽

Vol 50 (10) ◽

pp. 2139-2145

Author(s):

Alexander Muck ◽

Eva Šantavá ◽

Bohumil Hájek

Keyword(s):

Spectroscopic Study ◽

Infrared Spectra ◽

Point Of View ◽

Mixed Crystals ◽

Crystal Symmetry ◽

Infrared Spectroscopic Study ◽

X Ray Diffraction ◽

X Ray ◽

Infrared Spectroscopic ◽

Diffraction Patterns

The infrared spectra and powder X-ray diffraction patterns of polycrystalline YPO4-YCrO4 samples are studied from the point of view of their crystal symmetry. Mixed crystals of the D4h19 symmetry are formed over the region of 0-30 mol.% YPO4 in YCrO4. The Td → D2d → D2 or C2v(GS eff) correlation is appropriate for both PO43- and CrO43- anions.

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