III.—Review of the Evidence for the Animal Nature of Eozoön Canadense

1895 ◽  
Vol 2 (12) ◽  
pp. 545-550
Author(s):  
William Dawson
Keyword(s):  
Museum Specimens ◽  
Moderate Size ◽  
Proper Form ◽  
The Matrix ◽  
External Form

In recent years I have been disposed to attach more importance than formerly to the general form and macroscopical characters of Eozoön. The earlier examples studied were, for the most part, imbedded in the limestone in such a manner as to give little definite information as to external form; and at a later date, when Sir William Logan employed one of his assistants, Mr. Lowe, to quarry large specimens at Grenville and Côte St. Pierre, the attempt was made to secure the most massive blocks possible, in order to provide large slabs for showing museum specimens. More recently, when collections have been made from the eroded and crumbling surfaces of the limestone in its wider exposures, it was found that specimens of moderate size had been weathered out, and could, either naturally or by treatment with acid, be entirely separated from the matrix. Such specimens sometimes showed, either on the surfaces or on the sides of cavities and tubes penetrating the mass, a confluence of the laminæ, constituting a porous cortex or limiting structure. Specimens of this kind were figured in 1888, and I was enabled to add to the characters of the species that the original and proper form was “broadly turbinate with a depression or cavity above, and occasionally with oscula or pits penetrating the mass.” The great flattened masses thus seemed to represent confluent or overgrown individuals, often contorted by the folding of the enclosing beds.

scholarly journals VII - On the factors that influence external form of fossil plants; with descriptions of the foliage of some species of the Palaeozoic Equisetalean Genus Annularia Sternberg

1936 ◽  
Vol 226 (535) ◽  
pp. 219-237 ◽  
Keyword(s):  
Plant Tissues ◽  
Herbarium Specimens ◽  
Fossil Plants ◽  
Surrounding Matrix ◽  
The Matrix ◽  
Original Plant ◽  
Plant Fragment ◽  
External Form ◽  
Plant Forms

I — On the Factors which Influence the External Form of Fossil Plants Most writers of general treatises on Palaeobotany give an introductory chapter on fossilization, and this as a rule includes an account of the various kinds of fossil plants and the circumstances under which plants may become incorporated in sediments. The differences between the external form of the fossil and the original plant fragment are not often mentioned in relation to the factors which operate in the production of a fossil. It is often implied that fossil plants of the “ incrustation ” or “ impression ” type are produced in much the same way as herbarium specimens. That such a crude analogy does not satisfactorily explain the forms found among fossil plants of this type is obvious to those who have applied transfer methods to the examination of such fossils. In the writer’s opinion, the reason why so little precision has been given to descriptions of fossil-plant forms is that insufficient attention has been paid to the properties of sediments and the role played by the matrix. While many writers recognize that the differences in shape between a fossil and the original plant are due to the compressibility of the plant tissues the writer is not aware of any reference in the literature to the importance of the compressibility of the matrix in determining the form of a fossil embedded in it. It will be shown that the alteration in shape of a plant in undergoing fossilization in many cases may be best described as the result first of the collapse of the plant tissues and second of a more or less uniform vertical strain of the fossil and the surrounding matrix together.

scholarly journals II.—On an Aroideous Fruit from the Stonesfield Slate

1867 ◽  
Vol 4 (34) ◽  
pp. 146-147 ◽  
Author(s):  
Wm. Carruthers
Keyword(s):  
Transverse Section ◽  
Linear Series ◽  
Plate Viii ◽  
Calcareous Sand ◽  
The Core ◽  
Hexagonal Form ◽  
The Matrix ◽  
External Form ◽  
Short Tube

I owe my acquaintance with this interesting fossil to Mr. S. Stutterd, who kindly forwarded it to me for my inspection. It is from the Stonesfield Slate, and is preserved in limestone, but is only a cast formed in the matrix left in the rock after the organism itself had disappeared. The core had been hollow, or composed of a more speedily perishable material than the parietes, and so it rapidily disappered, permitting the empty axis to be filled with fragments of shells and calcareous sand. Externally, the cylindrical fossil is formed of sub-quadrangular peltate plates, with irregular undulate dentate margins, the projections of each of which fit into the undulations of the surrounding plates, and are arranged in linear series. A transverse section (Plate VIII. Fig. 2b.) shows each of these external plates to be the closed termination of a short tube, that has in the transverse section a hexagonal form. These tubes are filled in with a darker material, which, unfortunately, is without structure, and any determination of the affinities of the fossil must depend entirely on the external form, and the arrangement of the parts. Of necessity, these are defective and unsatisfactory materials; nevertheless, the fossil seems to me to present so remarkable an appearance, and so close an approximation to a portion of the inflorescence of an Aroideous plant, that I do not hesitate to refer it to this family; and I entertain the hope that one result of this notice and the accompanying figure may be to draw some attention to the fossil, which seems to be by no means rare, and so supply the means for more completely establishing its affinities.

scholarly journals XI. A description of some fossil plants, showing, found in the lower coal-seams of Lancashire and Yorkshire

1865 ◽  
Vol 155 ◽  
pp. 579-604 ◽  
Keyword(s):  
Internal Structure ◽  
Fossil Plants ◽  
Coal Seams ◽  
True Nature ◽  
Fossil Remains ◽  
The Matrix ◽  
Original Plant ◽  
External Form ◽  
Different Parts ◽  
Coal Fields

Although great attention has been devoted to the collection of the fossil remains of plants with which our coal-fields abound, the specimens are generally in very fragmentary and distorted conditions as they occur imbedded in the rocks in which they are entombed; but when they have been removed, cut into shape, and trimmed, and are seen in cabinets, they are in a far worse condition. This is as to their external forms and characters. When we come to examine their internal structure, and ascertain their true nature, we find still greater difficulties, from the rarity of specimens at the same time displaying both the external form and the internal structure of the original plant. It is often very difficult to decide which is the outside, different parts of the stem dividing and exposing varied surfaces which have been described as distinct genera of plants. The specimens were collected by myself, and taken out of the seams of coal just as they occurred in the matrix in which they were found imbedded, by my own hands. This enables me to speak with certainty as to the condition and locality in which they were met with.

Crystalloid Inclusions in Hepatocyte Mitochondria and Their Similarity to Cytoplasmic Crystalloids

1974 ◽  
Vol 32 ◽  
pp. 198-199
Author(s):  
Odell T. Minick ◽  
Hidejiro Yokoo
Keyword(s):  
Liver Disease ◽  
Alcoholic Liver Disease ◽  
Special Interest ◽  
Structural Variations ◽  
Mitochondrial Alterations ◽  
The Matrix ◽  
Crystalloid Inclusions ◽  
Liver Biopsies

Mitochondrial alterations were studied in 25 liver biopsies from patients with alcoholic liver disease. Of special interest were the morphologic resemblance of certain fine structural variations in mitochondria and crystalloid inclusions. Four types of alterations within mitochondria were found that seemed to relate to cytoplasmic crystalloids.Type 1 alteration consisted of localized groups of cristae, usually oriented in the long direction of the organelle (Fig. 1A). In this plane they appeared serrated at the periphery with blind endings in the matrix. Other sections revealed a system of equally-spaced diagonal lines lengthwise in the mitochondrion with cristae protruding from both ends (Fig. 1B). Profiles of this inclusion were not unlike tangential cuts of a crystalloid structure frequently seen in enlarged mitochondria described below.

Coherency loss in γ' precipitates in nickel-base superalloy

1983 ◽  
Vol 41 ◽  
pp. 244-245
Author(s):  
R. A. Ricks ◽  
Angus J. Porter
Keyword(s):  
Lattice Mismatch ◽  
Lattice Parameter ◽  
Nickel Base Superalloy ◽  
Large Size ◽  
The Matrix ◽  
Nimonic 80A ◽  
Interfacial Dislocations ◽  
Nickel Base ◽  
Coherency Loss ◽  
Nimonic 115

During a recent investigation concerning the growth of γ' precipitates in nickel-base superalloys it was observed that the sign of the lattice mismatch between the coherent particles and the matrix (γ) was important in determining the ease with which matrix dislocations could be incorporated into the interface to relieve coherency strains. Thus alloys with a negative misfit (ie. the γ' lattice parameter was smaller than the matrix) could lose coherency easily and γ/γ' interfaces would exhibit regularly spaced networks of dislocations, as shown in figure 1 for the case of Nimonic 115 (misfit = -0.15%). In contrast, γ' particles in alloys with a positive misfit could grow to a large size and not show any such dislocation arrangements in the interface, thus indicating that coherency had not been lost. Figure 2 depicts a large γ' precipitate in Nimonic 80A (misfit = +0.32%) showing few interfacial dislocations.

Influence of Heat Treatments on Microstructures in an Fe-Co-V Alloy

1974 ◽  
Vol 32 ◽  
pp. 512-513
Author(s):  
S. Mahajan ◽  
M. R. Pinnel ◽  
J. E. Bennett
Keyword(s):  
Single Phase ◽  
Alloy Composition ◽  
Supersaturated Solid Solution ◽  
Cell Formation ◽  
Heat Treatments ◽  
Air Cooling ◽  
Iced Brine ◽  
Transmission Electron ◽  
The Matrix ◽  
Bcc Structure

The microstructural changes in an Fe-Co-V alloy (composition by wt.%: 2.97 V, 48.70 Co, 47.34 Fe and balance impurities, such as C, P and Ni) resulting from different heat treatments have been evaluated by optical metallography and transmission electron microscopy. Results indicate that, on air cooling or quenching into iced-brine from the high temperature single phase ϒ (fcc) field, vanadium can be retained in a supersaturated solid solution (α2) which has bcc structure. For the range of cooling rates employed, a portion of the material appears to undergo the γ-α2 transformation massively and the remainder martensitically. Figure 1 shows dislocation topology in a region that may have transformed martensitically. Dislocations are homogeneously distributed throughout the matrix, and there is no evidence for cell formation. The majority of the dislocations project along the projections of <111> vectors onto the (111) plane, implying that they are predominantly of screw character.

Heterogeneity of Size and Distribution of Intramembrane Particles in the Plasma Membrane of Yeast

1977 ◽  
Vol 35 ◽  
pp. 596-597
Author(s):  
E. Keyhani
Keyword(s):  
Plasma Membrane ◽  
Candida Utilis ◽  
Synthetic Medium ◽  
Freeze Fracture ◽  
Translational Diffusion ◽  
Yeast Cells ◽  
Distilled Water ◽  
Intramembrane Particles ◽  
The Matrix ◽  
Water Cell

The matrix of biological membranes consists of a lipid bilayer into which proteins or protein aggregates are intercalated. Freeze-fracture techni- ques permit these proteins, perhaps in association with lipids, to be visualized in the hydrophobic regions of the membrane. Thus, numerous intramembrane particles (IMP) have been found on the fracture faces of membranes from a wide variety of cells (1-3). A recognized property of IMP is their tendency to form aggregates in response to changes in experi- mental conditions (4,5), perhaps as a result of translational diffusion through the viscous plane of the membrane. The purpose of this communica- tion is to describe the distribution and size of IMP in the plasma membrane of yeast (Candida utilis).Yeast cells (ATCC 8205) were grown in synthetic medium (6), and then harvested after 16 hours of culture, and washed twice in distilled water. Cell pellets were suspended in growth medium supplemented with 30% glycerol and incubated for 30 minutes at 0°C, centrifuged, and prepared for freeze-fracture, as described earlier (2,3).

Electron microscopy and diffraction studies of polyimides

1983 ◽  
Vol 41 ◽  
pp. 28-29
Author(s):  
O.C. de Hodgins ◽  
K. R. Lawless ◽  
R. Anderson
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Structural Features ◽  
Inert Atmosphere ◽  
Polyimide Films ◽  
Resolution Electron ◽  
The Matrix ◽  
High Resolution Electron Microscope ◽  
Diffraction Patterns ◽  
Polymeric Samples

Commercial polyimide films have shown to be homogeneous on a scale of 5 to 200 nm. The observation of Skybond (SKB) 705 and PI5878 was carried out by using a Philips 400, 120 KeV STEM. The objective was to elucidate the structural features of the polymeric samples. The specimens were spun and cured at stepped temperatures in an inert atmosphere and cooled slowly for eight hours. TEM micrographs showed heterogeneities (or nodular structures) generally on a scale of 100 nm for PI5878 and approximately 40 nm for SKB 705, present in large volume fractions of both specimens. See Figures 1 and 2. It is possible that the nodulus observed may be associated with surface effects and the structure of the polymers be regarded as random amorphous arrays. Diffraction patterns of the matrix and the nodular areas showed different amorphous ring patterns in both materials. The specimens were viewed in both bright and dark fields using a high resolution electron microscope which provided magnifications of 100,000X or more on the photographic plates if desired.

Organisation in the Structure of the Cytoplasmic Ground Substance

1978 ◽  
Vol 36 (3) ◽  
pp. 627-639
Author(s):  
K.R. Porter
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Complex ◽  
Random Distribution ◽  
Ground Substance ◽  
The Matrix ◽  
Cell Processes ◽  
Cytoplasmic Ground Substance

Most types of cells are known from their structure and overall form to possess a characteristic organization. In some instances this is evident in the non-random disposition of organelles and such system subunits as cisternae of the endoplasmic reticulum or the Golgi complex. In others it appears in the distribution and orientation of cytoplasmic fibrils. And in yet others the organization finds expression in the non-random distribution and orientation of microtubules, especially as found in highly anisometric cells and cell processes. The impression is unavoidable that in none of these cases is the organization achieved without the involvement of the cytoplasmic ground substance (CGS) or matrix. This impression is based on the fact that a matrix is present and that in all instances these formed structures, whether membranelimited or filamentous, are suspended in it. In some well-known instances, as in arrays of microtubules which make up axonemes and axostyles, the matrix resolves itself into bridges (and spokes) between the microtubules, bridges which are in some cases very regularly disposed and uniform in size (Mcintosh, 1973; Bloodgood and Miller, 1974; Warner and Satir, 1974).

Electrolytic Isolation of Twin-Type Shock Deformation Structures

1967 ◽  
Vol 25 ◽  
pp. 318-319
Author(s):  
F. I. Grace ◽  
L. E. Murr
Keyword(s):  
Grain Boundaries ◽  
Thin Foil ◽  
Electrolyte Composition ◽  
Experimental Conditions ◽  
Average Current Density ◽  
Electron Transmission ◽  
Deformation Structures ◽  
The Matrix ◽  
Average Current ◽  
Specimen Edge

During the course of electron transmission investigations of the deformation structures associated with shock-loaded thin foil specimens of 70/30 brass, it was observed that in a number of instances preferential etching occurred along grain boundaries; and that the degree of etching appeared to depend upon the various experimental conditions prevailing during electropolishing. These included the electrolyte composition, the average current density, and the temperature in the vicinity of the specimen. In the specific case of 70/30 brass shock-loaded at pressures in the range 200-400 kilobars, the predominant mode of deformation was observed to be twin-type faults which in several cases exhibited preferential etching similar to that observed along grain boundaries. A novel feature of this particular phenomenon was that in certain cases, especially for twins located in the vicinity of the specimen edge, the etching or preferential electropolishing literally isolated these structures from the matrix.

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