Amorphous Background Research Articles

Sem and Aes Analysis of Ion Implanted Graphite

ABSTRACTIon-implantation of graphite is characterized with respect to lattice damage and the distribution of implanted ions. Both the depth profile of the implanted ions and of the lattice damage are shown to follow the models previously developed for ion-implanted semiconductors. Auger electron spectroscopy (AES) is used to monitor the implantation profile. The surface damage is examined by scanning electron microscopy (SEM) while microcrystalline regions in an amorphous background are observed by scanning transmission electron microscopy (STEM).

Ultrastructural features of eosinophil leucocytes of the goat: I. Granules development in the bone marrow

The ultrastructure of the eosinophil leucocytes and the development of their granules were studied in the bone marrow of the goat ( Caprinae capra). Three distinct forms consisting of early, intermediate and mature stages were recognized. The granules developed from the dilated endoplasmic reticulum and assumed the mature crystalloid form in the early intermediate stage when the Golgi complex appeared very prominent. The mature granules were of several shapes; the prominent variant contained tubular profiles against a less dense amorphous background. The role of a rough endoplasmic reticulum and the Golgi complex in the development of the eosinophil granulocytes is compared with their role in the classical pathways of the secretory apparatus.

Modelling of the x‐ray scattering of polymers by light diffraction

AbstractThe x‐ray patterns of solid phase polymers are widely used to characterize the structures. They can be used, among others things, to calculate the degree of crystallinity, the crystalline particle size, and the lattice distortions. However, it is not perfectly clear how the characteristics of the structure effect the obtained diffractograms. The main aim of the present work is to explain what kind of diffraction patterns can be obtained from a hypothetical structure of a polymer. The effect of the following structural parameters were investigated: degree of crystallinity, crystalline particle size, lattice distortions of the first and second kind, and amorphous background. The changes of the diffraction patterns depending on these varied factors were followed.The light diffraction patterns were produced by a modified Schlieren 80 apparatus. The polymer segments were modelled by point‐like scattering centers. From these, the models of an ideal crystal and the lattice distortion of the first and second kind were prepared. The crystalline particle size was varied by cutting the original mask. In the amorphous background the minimum distances of two scattering centers were altered. The light diffraction patterns were produced also by rotating the mask, and the x‐ray diagram of the unoriented polycrystalline samples could be reproduced. The intensities of the obtained patterns were measured by a microdensitometer. With the help of the diagrams, both qualitative and quantitative conclusions can be obtained about the relation between the mask and its diffraction pattern.

Determination of crystallinity in polyester fibers by x‐ray methods

AbstractThe methods of Hermans and Weidinger and of Wakelin et al. (the correlation and integral methods) were used to determine the degree of crystallinity in poly(ethylene terephthalate) (PET) fibers. A standarization of cutting of the amorphous background scattering in PET fibers, indispensable for the method of Hermans and Weidinger, is put forward. On using a partial standardization of the intensity diffracted and scattered in the fiber, namely, on taking into account the x‐ray density of the specimen, variability in the intensity due to differences in absorption in the specimen at different angles 2θ and variability in the specimen mass reflecting x‐rays in the function of the diffraction angle, good agreement of the PET fiber crystallinity values is observed.

Preparation and properties of nexuses and lipid-enriched vesicles from mouse liver plasma membranes.

Extraction of mouse liver plasma membranes with 4% (w/v) N-laurylsarcosinate-tris buffer, pH7.8, solubilized 80-90% of the protein and 60% of the 5'-nucleotidase activity. The membrane residue remaining after extraction was resolved on sucrose gradients into two fractions: a vesicular membrane fraction and a fraction characterized by the presence of large numbers of nexuses in an amorphous background. The vesicular fraction had a phospholipid/protein weight ratio of 7:1, it contained most of the plasma-membrane glycolipids, and polyacrylamide-gel electrophoresis indicated the presence of only five to eight proteins, including two or three glycoproteins. The 5'-nucleotidase and leucine naphthylamidase specific activities were 23- and 6-fold higher respectively than in the plasma membranes. Electron microscopy of thin sections and negatively stained preparations indicated that the nexuses present in the second fraction closely resembled gap junctions present in tissue sections and isolated plasma membranes. The nexus fraction contained a distinctive protein pattern, and of the 20 proteins present about four were identified as glycoproteins by Schiff-periodate staining. Examination of the lipid composition of the fractions by t.l.c. showed that in the nexus fraction, phospholipids and glycolipids were present in small amounts compared with triglycerides and cholesterol. Amino sugar analyses confirmed the t.l.c. results and amino acid analysis showed the fractions to have characteristic protein compositions. A ;reconstituted' membranous fraction prepared by dialysis against MgCl(2) of membrane components soluble in N-laurylsarcosinate-tris buffers, pH7.8, lacked the trilaminar image characteristic of the two other membrane fractions isolated and was devoid of enzyme activities. The results indicate that proteins and glycoproteins play an important role in the structural maintenance of the nexuses isolated from the liver by the present procedure.

The ultrastructure of the test of the tadpole larva ofCiona intestinalis

The test of the tadpole larva ofCiona intestinalis consists of an amorphous background substance in which are long 4–7 nm fibrils. There is a narrow outer dense region of the test where both the background material and the test fibrils are more concentrated and orientated. Fibrils of similar dimensions are found in the epithelial cells below the test, and also in cells associated with the outside surface of the test. No such fibrils are found in the cells located within the test substance. There are some regions where the external cell membrane of the epithelial cells is indistinct and in these regions the fibrils of the test are continuous with the fibrils within the epithelial cells. No large or small vesicles opening from the epithelial cells into the test have been seen.

A CASE OF FAHR'S DISEASE WITH AN UNUSUAL PERIVASCULAR PAS-POSITIVE MATRIX IN THE MOLECULAR LAYER OF THE CEREBELLAR CORTEX

Summary In a case of Fahr's disease an unusual PAS-positive perivascular matrix with amorphous background substances and fine trabeculae developed in the molecular layer of the cerebellar cortex. The significance of this matrix is remained as obscure.

Observation of Slip In Nylon 66 and 610 and Its Interpretation in Terms of a New Model

Crystalline slip has been observed in singly and doubly oriented nylon 66 and 610 by deformation of bristles in compression parallel to their orientation direction to form kink bands. The angles of the bands correspond to two and three (010) planes acting in unison as lamella in the kinking process. Slip was also manifested along a unique crystallographic plane (010) and a unique crystallographic direction ([1,3,14] and [1,3,18] in nylon 66 and 610) during fracture experiments on doubly oriented bristles. To account for this behavior a model of the structure of these oriented polymers is proposed in which the material is considered essentially completely crystalline with many vacancies and dislocations within the lattice. The dislocations and their motions which account for the observed deformations are illustrated. The difference between observed values of density and the theoretical density of nylon 66 is attributed to vacancies. The so-called amorphous background in x-ray diffraction patterns of these nylons is attributed to the vacancies and dislocations in the crystal structure.

Observations on function, composition, and structure of cestode calcareous corpuscles

1. 1. Taenia taeniaeformis contains about half as much calcareous corpuscle material as does Cysticercus fasciolaris. The corpuscles show no quantitative gradient along the strobila of Taenia taeniaeformis, but the larger individual proglottids contain more corpuscle material than the smaller ones. 2. 2. More calcareous material disappears from Cysticercus faciolaris during anaerobic than during aerobic incubation in non-nutritive media. In both cases considerably more corpuscle material disappears when the worms are incubated in slightly acid than in slightly alkaline surroundings. It is concluded that the corpuscles serve to buffer acids entering the body from the outside and, possibly, to buffer acids produced during aerobic and anaerobic fermentations. 3. 3. The corpuscles yield Ca, Mg, P, and CO 2. The mineral component of the corpuscles is amorphous, but upon heating with KOH crystallization takes place and brucite and hydroxyapatite crystals are formed. The carbonates, however, do not crystallize. 4. 4. Electron microscopy indicates that the lamellae of the corpuscles may be paired rings. It reveals also an amorphous or granular background substance, but no crystalline elements. 5. 5. The inorganic material of the corpuscles can readily be demonstrated by various histochemical staining methods. It is also possible to demonstrate histochemically a glycogen-like polysaccharide, a mucopolysaccharide, lipids, and proteins as constituents of the organic base of the corpuscles.

X-Ray Analysis of the Molecular Structure of Rubbers. X-Ray Diffraction of Amorphous Rubber

Abstract The potentialities of x-ray analysis of the molecular structure of rubbers can be widely extended by measuring the intensities of the amorphous halo and continuous background of scattering in the diffraction patterns of unstretched test-specimens. This method can be applied to the study of the effect of repeated stretching of rubbers. Questions pertaining to the fatigue of rubbers have immense importance now in the performance of rubber products. The methods of determining the crystallization of natural rubber and of measuring the intensity of the amorphous halo for synthetic rubber were employed for investigating the changes of the molecular structure of rubber due to repeated stretching. The crystallization of raw smoked-sheet rubber decreased as a result of fatigue; a similar phenomenon was observed for its vulcanizates. The vulcanizates which were stretched less than 300 per cent lost their crystallization property altogether after fatigue, and, at greater elongations, the content of the crystalline phase greatly decreased (see Figure 1).