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  • 1980-1984  (13.349)
  • 1983  (6.819)
  • 1980  (6.530)
  • Chemistry  (13.123)
  • Ultrastructure  (226)
Materialart
Erscheinungszeitraum
  • 1980-1984  (13.349)
Jahr
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 399 (1983), S. 191-205 
    ISSN: 1432-2307
    Schlagwort(e): Membranous lipodystrophy ; Fat tissue ; Ischemic necrosis ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Subcutaneous fat from 3 patients with ischemic necrosis of the legs due to arteriosclerotic obstruction were examined histologically and ultrastructurally. Markedly convoluted membranocystic changes were found in all 3 cases. The light and electron microscopic findings of the membranocystic lesions are very similar to those of fat tissue changes in membranous lipodystrophy. Bone lesions and mental disturbance which suggest membranous lipodystrophy, however, were absent in these cases. It is concluded from these results that the membranocystic changes characteristic of membranous lipodystrophy can be produced by circulatory disturbance and the lesions are one of the non-specific changes of adipose tissue.
    Materialart: Digitale Medien
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  • 2
    ISSN: 1432-2307
    Schlagwort(e): Pituitary adenoma ; Ultrastructure ; Immunocytochemistry ; Acromegaly ; Hyperprolactinemia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Nine cases of a hitherto undescribed morphologic entity, termed mammosomatotroph cell adenoma of the human pituitary, are reported. These tumors, occurring mostly in men, are invariably associated with acromegaly (or gigantism) and high-normal or slightly elevated blood prolactin levels, and it cannot be distinguished clinically from well-differentiated growth hormone cell or mixed growth hormone cell-prolactin cell adenomas. They show a slow growth rate and usually exhibit a diffuse pattern and intense cytoplasmic acidophilia by histology. The immunoperoxidase technique detects both growth hormone and prolactin within the same cells. Electron microscopy reveals monomorphous tumors with a fine structure markedly similar to that of well-differentiated, densely granulated growth hormone cell adenomas. An added feature and diagnostic marker of mammosomatotroph cell adenoma is the presence of extracellular deposits of secretory material. One tumor shows a marked abnormality of hormone packaging and storage, resulting in the cytoplasmic accumulation of pleomorphic bodies containing semicrystalline secretory material.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 401 (1983), S. 163-175 
    ISSN: 1432-2307
    Schlagwort(e): Breast ; Human ; Pregnancy ; Ultrastructure ; Morphology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In this study the structural changes which occur during human pregnancy were examined by light and electron microscopy. Pregnancy was associated with proliferation and differentiation of the epithelial cells within the lobules. Proliferation was continuous throughout pregnancy with a progressive increase in the size of the lobules. The highest level of mitosis was observed in the first trimester with lower levels in the second and third trimesters. Unexpectedly a number of apoptotic cells were observed during pregnancy. Differentiation was initiated in the second trimester with an increase in the amount of rough endoplasmic reticulum and the appearance of a hypertrophic Golgi body and lipid droplets within a number of epithelial cells. A number of small vacuoles were present close to the apical plasmalemma of a few epithelial cells. As the pregnancy proceeded there was an increase in the number of cells exhibiting these features. There was also an increase in the size of the lipid droplets and the number of apical vacuoles. The apical vacuoles which have not been described previously range in size from 150–600 nm with the contents of the larger vacuoles having a whorled or labyrinth-like appearance.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 399 (1983), S. 177-189 
    ISSN: 1432-2307
    Schlagwort(e): Achilles tendon ; Tendon injuries ; Muscles ; Myofibrils ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Unilateral tenotomy of the Achilles tendon was carried out in 60 rabbits. The limb was then either mobilized directly or immobilized for 10 to 35 days using a plaster usually after tendon suture. In certain cases the plaster was removed early (on the 7th or 16th day) and the animals were than allowed to use this leg. Separation between tendon ends was apparent from steel markers, placed close to each cut end of the tendon and examined by X-ray. The separation curve was biphasic and both the first and the inactive phase reflected the degree of tension over the tendon suture. However, during the second separation phase, which began between the 17th and 21st day, the separation gradually reached the same level in all groups. Enzyme histochemistry and electron microscopy revealed severe degenerative changes in immobilized and in shortened muscles. Furthermore, a gradual shift in fibre type characteristics from type 1 slow-twitch fibres towards type 2 fast-twitch fibres occurred. Rapid recovery followed removal of the plaster. The findings indicated that both degenerative and regenerative processes and adaptive processes had been initiated in all experimental muscles when the tendon continuity was broken. The adaptive processes progressed gradually during the five-week post-operative period and might have been responsible for the second phase of the tendon end separation. The fibre adaptation, i.e. the transformation, may be accounted for by changes in structure of the myofibrils and composition of the myosin molecules.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 401 (1983), S. 251-260 
    ISSN: 1432-2307
    Schlagwort(e): Congenital epulis ; Ultrastructure ; Granular cells ; Intracellular collagen fibrils
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary This report presents the ultrastructural features of a congenital epulis. The granular cells of the epulis were packed with numerous membrane bound cytoplasmic granules containing particles, small vesicles, and electron-dense materials. These granules were negative in immunohistochemical reaction for CEA (DAKO PAP KIT). Cytoplasmic organelles such as mitochondria, rough surfaced endoplasmic reticulum, and Golgi apparatus, were absent. Nuclei were markedly indented. Occasionally, banded intracellular collagen fibrils were observed within the cytoplasm. Some of these fibrils were surrounded by a limiting membrane, whereas others appeared to lie free in the cytoplasm. The collagen fibrils were also seen within a deep invagination of the cell surface. There was no basal lamina around the granular cells. Sporadically, mast cells with many granules containing lamellar formations were found between the granular cells. These observations support the idea that granular cells of the congenital epulis are derived from mesenchymal cells, probably fibroblasts.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 399 (1983), S. 277-287 
    ISSN: 1432-2307
    Schlagwort(e): Pituitary ; Hyperplasias ; Immunocytochemistry ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Surgical specimens of 15 normal and 106 para-adenomous anterior pituitaries were studied immunocytochemically and in part electron microscopically for the presence of hyperplasia. GH cell hyperplasia was found in 13% of all normal pituitaries, in 6% of the cases with Prolactin secreting adenomas and in 9% of the cases with ACTH secreting adenomas. Prolactin cell hyperplasia occured in nearly equal percentages (17–23%) in normal pituitaries and in areas adjacent to GH-, Prolactin-or ACTH-secreting adenomas or adjacent to inactive adenomas. Previous findings of relatively more frequent Prolactin cell hyperplasia occuring together with Prolactin producing adenomas have to be revised. Prolactin cell hyperplasia as a primary source of hyperprolactinemia is very rare and almost always occurs in conjunction with oncocytic adenomas. ACTH cell hyperplasia was found in 13% of the normal pituitaries, in 14% of the cases with Prolactin secreting adenomas, in 58% of the cases with ACTH producing adenomas and in 40% of the pituitaries with GH secreting adenomas. We have no explanation for the latter result. ACTH cell hyperplasia may be the primary cause of Cushing's disease (18% of all Cushing cases). Hyperplasia of TSH cells in normal pituitaries was rare (7%) and with the exception of Prolactin producing adenomas (22%) was not found near adenomas. Clinical-pathological correlations are discussed.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 400 (1983), S. 143-154 
    ISSN: 1432-2307
    Schlagwort(e): Experimental autoallergic sialadenitis ; Mice ; Submandibular gland ; Histopathology ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Experimental autoallergic sialadenitis was induced in SL/Ni mice by one or two injections of syngeneic submandibular gland homogenate emulsified with adjuvant. Light microscopically, there were marked lymphoid cell infiltration in the submandibular glands with high incidence and proliferation of duct epithelia. Furthermore complete alteration of whole glandular lobules in some cases was observed. Ultrastructurally, small and medium sized lymphocytes and plasma cells constituted a major portion of the infiltrating cells, and lymphocytes were frequently observed inside the basal lamina of ductal and acinar regions, especially observed in the small ductal region. In the aggregates of infiltrating cells, the cell remnants of salivary gland epithelia were scattered. Furthermore some of the epithelial cell remnants in aggregates of infiltrating cells could be recognized as epithelial masses which were composed of proliferated duct epithelial cells, though no typical structure of epimyoepithelial islands seen in Sjögren's syndrome was found. Anti-salivary duct antibody was detected in only one case.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 401 (1983), S. 89-97 
    ISSN: 1432-2307
    Schlagwort(e): Undifferentiated carcinoma ; Parotid gland ; Myoepithelial cell ; Epithelial cell ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Two cases of undifferentiated carcinoma of the parotid gland were studied by light and electron microscopy. Light microscopy showed nests of ovoid cells with scanty cytoplasm and pyknotic nuclei in two cases. One case was the small-cell type, and another one was the large-cell type histopathologically. Electron microscopy showed two distinct cell types in each tumor: Case 1 (small-cell type). — An epithelial-like cell, and an irregular-shaped cell containing bundles of filaments suggesting myoepithelial differentiation. Case 2 (large-cell type). — An epithelial-like cell, and a large cell containing secretory-like granules. These findings support a salivary duct epithelial origin for these tumors.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 166 (1983), S. 121-134 
    ISSN: 1432-0568
    Schlagwort(e): Uterine glands ; Pig ; Ultrastructure ; Cytochemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The ultrastructure of the porcine uterine glands is described from material taken from 11 pregnant pigs at exactly known stages of gestation (day 30; 58; 80; 100; 110). Fixation was performed by perfusion via a branch of the uterine artery and the tissue was routinely processed for electrom microscopy. Additionally, cytochemical studies (phosphotungstic acid reaction for glycoproteins, according to Rambourg 1967; acid phosphatase reaction; ultrastructural localization of cellular iron, according to Parmley et al. 1978) were performed. On day 30 of pregnancy the uterine glands are coiled, simple tubular glands with a narrow lumen. The epithelial lining is simple columnar and consists basically of two cell types, ciliated cells and secretory cells. The secretory activity of the glandular epithelium is low; only a few secretory granules are present in the supranuclear cytoplasm. At midpregnancy the ultrastructure of the glands has significantly changed and the cells now show all the characteristics of high secretory activity: numerous parallel cisternae of rough endoplasmic reticulum, an extensively developed Golgi apparatus and many secretory granules which give a positive reaction for acid phosphatase and glycoproteins. The lumina of the glands are significantly enlarged and filled with a great amount of a granular, acid phosphatase-positive material. In the last third of pregnancy, only minor changes in the ultrastructure of the uterine glands are observed. The secretory activity is still high. The amount of rough endoplasmic reticulum has further increased and parallel arrays of cisternae occupy a considerable part of the supranuclear cytoplasm. The importance of the uterine secretion for embryonic nutrition and development is only partly understood. One of the secreted glycoproteins, uteroferrin, is believed to play an important role in the iron transfer from mother to fetus. From midpregnancy onward, a special cell type, the “granule laden cell” is found scattered between normal secretory cells of the uterine glands. Contrary to the opinion of Perry and Cromby (1982), we could demonstrate that these cells frequently extend to the lumen of the gland; hence the term “basal cell” seems inappropriate for this cell type.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 166 (1983), S. 263-274 
    ISSN: 1432-0568
    Schlagwort(e): Decidua ; Ultrastructure ; Mouse
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The ultrastructure of mouse antimesometrial decidual cells was analyzed during the development of the decidua between days 5 and 8 of pregnancy. The first decidual cells, appearing on the 5th day, are polygonal with rounded nuclei and prominent nucleoli; free ribosomes predominate in the cytoplasm. On the 6th to the 8th days the cytoplasm of these cells is typically that of cells actively engaged in macromolecular synthesis. Large numbers of granular and agranular endoplasmic reticulum cisternae are present in addition to well-developed Golgi complexes, mitochondria and lysosomes. Many bundles of microfilaments and lipid droplets occur during this period. An intense accumulation of autophagosomes and lysosomes with very heterogeneous content was noted on the 7th and especially the 8th days. The presence of these organelles is an indication that involution of this part of the decidua has begun.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 168 (1983), S. 51-58 
    ISSN: 1432-0568
    Schlagwort(e): Bulbospongiosus muscle ; Histochemistry ; Ultrastructure ; Castration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The histochemical profile and ultrastructural properties of the bulbospongiosus muscle (BSM) fibers from 5–6 month old boars and barrows (castrated at 7 days of age), and intact week old piglets were compared. Based on myosin ATPase, preincubated at pH 4.2, BSM of boars contained predominately intermediately staining fibers, whereas BSM of barrows and piglets had a mixture of staining intensities. Fibers from boar BSM stained intensely for SDH, with subsarcolemmal and diffuse location of reaction product. Staining intensity for SDH was variable in BSM from barrows and piglets, with diffuse location of reaction product. The BSM of boars and barrows contained predominately dark fibers when stained for glycogen and phosphorylase, and the fibers were low in stored lipids. While the fibers were smaller in barrow as compared to boar BSM, ultrastructural differences between boar and barrow BSM were not detectable.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 168 (1983), S. 195-209 
    ISSN: 1432-0568
    Schlagwort(e): Epididymis ; Guinea pig ; Principal cells ; Zonula occludens ; Zonula adhaerens ; Ultrastructure ; Freeze fracture
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The junctional complexes of the principal cells in the guinea pig epididymis were analyzed using freeze fracture and ultrathin section goniometric techniques. Replicas of the seven regions (I to VII) investigated reveal a continuous decrease in the number of tight junctional strands, ranging from 15.73±3.54 in zone I (proximal) to 4.39±0.78 in zone VII (distal tubule). The distance from the adluminal to the basolateral strand also diminishes from proximal, 0.73±0.02 μm to distal, 0.19±0.03 μm. The junctional strands appear on the P-face and anastomose forming compartments which are larger in the basolateral areas than those in the apical. The network of strands frequently form terminal loops and blind endings towards the more basal parts of the lateral membrane. Freeze fracture images also exhibit randomly distributed particulate aggregations which correspond to maculae adhaerentes, the highest number of which are found in zone IV, V, and VII. Desmosomal figures are found not only below, but also adjacent and intermingled among the tight junctional strands. This special junctional arrangement is confirmed upon goniometric analysis of ultrathin sections from zones IV, V, and VII. Electron dense desmosomal plaques are seen parallel and directly subjacent to the membranes of the tight junctions, following the strands in both directions to finally converge on the punctiform connections. Goniometry also reveals a dense feltwork of material closely applied along the lateral cell border. These zonulae adhaerentes are seen to be of greatest length and density in zones I, VI, and VII.
    Materialart: Digitale Medien
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 168 (1983), S. 349-359 
    ISSN: 1432-0568
    Schlagwort(e): Breast ; Human ; Lactation ; Ultrastructure ; Morphology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In this study the morphological features of lactation in the human breast were examined by scanning and transmission electron microscopy. The lactating lobules comprised large numbers of interconnecting acini which were lined by a single layer of epithelial cells with underlying myoepithelial cells. Marked variations were noted in the shape of the epithelial cells. The myoepithelial cells formed an open meshwork of interconnecting cytoplasmic processes packed with myofibrils. The basal cytoplasm of the epithelial cells was packed with rough endoplasmic reticulum while the apical cytoplasm contained a hypertrophic Golgi body, numerous vacuoles (a few of which contained casein micelles), a number of lipid droplets and small coated and uncoated vesicles. The lipid droplets were released by progressive protrusion from the apical surface. They remained covered by the plasmalemma and were finally budded off into the lumen. In certain cases a portion of cytoplasm was released with the lipid droplet. The vacuoles and small vesicles fused with the plasmalemma and released their contents by exocytosis. Within the samples the majority of epithelial cells were actively lactating although examples of undifferentiated “resting” and dead (lysed) cells were also identified.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 168 (1983), S. 173-194 
    ISSN: 1432-0568
    Schlagwort(e): Epididymis ; Guinea pig ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The guinea pig epididymis is subdivided into seven zones. The ultrastructure and morphology of the principal cells in these zones is analyzed. The position, shape and content of the nuclei are variable along the length of the epididymal duct. Features characteristic of absorptive activity, such as micropinocytotic caveolae, vacuoles, and multivesicular bodies are of high concentration in zone IV and VI. The Golgi apparatus, rough endoplasmic reticulum and secretion granules are organelles and inclusions implicated to secretory functions and in this study are not found in the following concurring amounts within the principal cells of the seven zones: the Golgi apparatus exhibits a trend of increase from zone II to zone VII while the rough endoplasmic reticulum decreases. Secretion granules, though, are detected only in zones II and III, not only in the supra-, but also in the peri-and infranuclear regions. This possibly implies an exocrine secretory functions. Lamellar whorls and profiles of tubular smooth endoplasmic reticulum are concentrated in the supranuclear and adluminal regions of zones I, II and VI. A high concentration of large lipid droplets is a consistent feature of the perinuclear region of zone II. Mitochondia and lysosomes are detected in relatively large amounts along the epididymal duct. The correlations of these morphological characteristics with respect to their possible functional role are discussed.
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 168 (1983), S. 331-339 
    ISSN: 1432-0568
    Schlagwort(e): Ultrastructure ; Starvation ; Absorptive cells ; Small intestine ; Rats
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The ultrastructure of the absorptive cells in the duodenum, jejunum and ileum after 7, 14 and 21 days of starvation was investigated using rats aged from 12 to 18 months weighing about 500 g. In the basal cytoplasm of the absorptive cells (in the duodenum and ileum of 21-day-starved rats and the jejunum of 14- and 21-day-starved rats), the following changes were found: atrophied mitochondrion-like bodies, small vesicles, a short and sparse rough-surfaced endoplasmic reticulum and a lack of density in a portion of the cytoplasm. Moreover, many autolysosomes of various sizes and shapes were encountered in the basal cytoplasm; occasionally these elements accumulated and appeared to fuse to one another. In contrast, in the apical cytoplasm of absorptive cells in the intestine of starved rats, the ultrastructure was similar to that of control rats. It was considered that the apical cytoplasm of the absorptive cells in the starved rat intestine might be preserved as long as possible during starvation in order to absord nutrients when they become available again.
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 166 (1983), S. 317-332 
    ISSN: 1432-0568
    Schlagwort(e): Dentate gyrus ; 3H-thymidine ; Glial cells ; Proliferation ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Tritiated thymidine autoradiography has established that after interrupting the commissural afferents to the dentate gyrus a number of non-neuronal cells proliferate in the molecular layer. In the present study the fine structure of the proliferating cells was analyzed by reembedding the 2-μm thick plastic sections of the dentate gyrus which had been previously coated with a nuclear emulsion and processed for light microscopic autoradiography. The location of the labeled cells was plotted with a camera lucida and a few ultrathin sections were taken from the re-embedded sections. In these the labeled cells were re-identified and photographed in an electron microscope. Most of the identified proliferating cells exhibited the following morphological features: The nuclei were irregularly oval, sometimes with deep indentations and contained dense clumps of chromatin; their diameters ranged between 4.5 and 6.5 μm. The cytoplasm was generally disposed to one side of the nucleus and often extended into a few broad processes. The Golgi apparatus was well developed. Many rosettes of free ribosomes were scattered throughout the cytoplasm, and the rough endoplasmic reticulum usually consisted of a few short cisternae. Small multilamellated bodies were common, but dense inclusion bodies were infrequent. The observations reported in this paper suggest: 1. that the nonneuronal cells which proliferate in a neuropil undergoing a mild denervation are morphologically closely related to microglia; 2. that in young adult animals these cells do not seem to have been previously involved in intense phagocytic activity; and 3. that the proliferating cells are present in the neuropil at the time of the denervation.
    Materialart: Digitale Medien
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 192 (1983), S. 42-44 
    ISSN: 1432-041X
    Schlagwort(e): Chick embryo ; Gastrulation ; Adenylate cyclase ; cAMP phosphodiesterase ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The ultrastructural localization of adenylate cyclase (E.C. 4.6.1.1.) and cAMP phosphodiesterase (PDE) (E.C. 3.1.4.17.) in the ectoderm of the developmental stage 4 chick embryo was studied. Adenylate cyclase was localized in the lateral surfaces of the ectodermal cells. In the primitive streak cells the enzymatic activity was observed on all the lateral surfaces, whereas in the periphery of the blastoderm the reaction product was localized in the apical parts of the lateral plasma membranes only. cAMP PDE localized in the apical cytoplasm of the ectodermal cells, with highest activity in the globular projections.
    Materialart: Digitale Medien
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 59 (1983), S. 277-282 
    ISSN: 1432-0533
    Schlagwort(e): Trauma ; Missile head injury ; Astrocyte ; Blood brain barrier ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Experimental high velocity missile brain injury in the rhesus monkey produces widespread swelling of perivascular astrocytes within 30 min of injury. Possible mechanisms for this lesion include a direct effect of force, chemical mediation secondary to the extravasation of blood, alterations in the permeability of the blood brain barrier and ischaemia. The implications of this finding for the function of the blood brain barrier, for neurotransmission and for neuronal survival are discussed.
    Materialart: Digitale Medien
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 62 (1983), S. 141-144 
    ISSN: 1432-0533
    Schlagwort(e): Ependymoma ; Clear cells ; Oligodendroglioma-like cells ; Mixed glioma ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A brain tumor of a 22-year-old man was composed mostly of round cells with perinuclear halos (clear cells), forming clusters intersected by small blood vessels. In some areas, the tumor cells showed perivascular arrangement and epithelial pattern. Phosphotungstic-acid hematoxylin stain and immunoper-oxidase stain for glial fibrillary acidic protein (GFAP) technique failed to stain the clear cells. Electron microscopy of the clear cells revealed them to be classical ependymoma cells with well developed intercellular junctions, microvilli and cilia. As no reporters in the past showed the evidence to clarify the nature of the clear cells, this case is considered a good example to support the viewpoint that the clear cells (oligodendroglioma-like cells) commonly observed in ependymomas are in reality ependymoma cells. It is stressed that the diagnosis of “mixed glioma” or “oligoependymoma” should be made with sufficient caution despite the recent advances of GFAP technique.
    Materialart: Digitale Medien
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Archives of dermatological research 275 (1983), S. 86-91 
    ISSN: 1432-069X
    Schlagwort(e): Vermilion of the lip ; Leukoplakia ; Epidermolytic hyperkeratosis ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A leukoplakic lesion of the lip showing the histologic features of epidermolytic hyperkeratosis above solar elastosis was investigated by electron microscopy. The ultrastructural alterations observed in the upper epidermal layers corresponded in the main with those of epidermolytic hyperkeratosis in other skin diseases. The keratinocytes showed irregularly formed tonofilaments, a marked intracellular edema, and premature cornification. In addition, there were discrete subcellular signs of premalignancy in the cells of the basal and suprabasal layers. These alterations suggest that the epidermolytic leukoplakia represents a rare histopathologic variant of actinic cheilitis.
    Materialart: Digitale Medien
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  • 21
    ISSN: 1432-072X
    Schlagwort(e): Cyanobacteria ; Ultrastructure ; Nitrogen fixation ; Water stress ; Taxonomy ; DNA ; Plasmids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Two strains of desiccation-tolerant coccoid cyanobacteria, Chroococcus S24, a marine form, and Chroococcus N41, a cryptoendolith isolated from a hot-desert rock, have been characterized. The mol % DNA base compositions of the strains are 47.1 and 48.9% respectively. Plasmid DNA was not detected in either strain. The pigment contents and nutritional characteristics of the strains are identical. Both lack phycoerythrinoid pigments and, in culture, behave as slow-growing halotolerant marine forms with elevated requirements for Na+, Cl−, Mg2+ and Ca2+. Sucrose was the only carbon source of those tested that supported photoheterotrophic growth. Each strain synthesizes nitrogenase under anaerobic conditions but not in air. Morphologically the two strains are indistinguishable. They are considered to be independent isolates of the same cyanobacterial species. Chroococcus N41 was studied in detail with the electron microscope. When brought to equilibrium at matric water potentials of-168 MPa and lower (to-673 MPa=c0.12a w) the protoplast shrinks, but the cells maintain the same size and diameter as those at-2,156 kPa (MN medium; control); the sheath expands and remains attached to the cell wall outer membrane by fibrils. The cell wall, cell membrane, thylakoid membranes, cyanophycin granules and carboxysomes appeared intact in desiccated cells.
    Materialart: Digitale Medien
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 51 (1983), S. 192-198 
    ISSN: 1432-1106
    Schlagwort(e): Flocculus ; Nucleus prepositus hypoglossi ; Ultrastructure ; Degeneration ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Small electrolytic lesions were made in the flocculus of two adult cats by means of a stereotactic approach avoiding any damage to the cerebellar nuclei. After a survival time of 3 days the animals were killed and the brains fixed and prepared according to standard procedures for ultrastructural studies. The brains of two unoperated cats were similarly treated and served as normal controls. In the experimental animals a large number of boutons in the rostral part of the nucleus prepositus hypoglossi (Ph) ipsilateral to the floccular lesion showed degenerative changes. These were characterized by hypertrophy, a prominent aggregation of densely packed parallel tubules or concentric arrays of cisternae and a filamentous hyperplasia. Only very rarely were such abnormal boutons seen in the caudal half of the ipsilateral Ph, or on the contralateral side or in the unoperated animals. The degenerating boutons contain clusters of pleomorphic vesicles and they establish symmetrical synaptic contacts with somata, dendritic shafts and dendritic spines. Some of the degenerating boutons appear to be of the en passant type. These findings thus affirm the existence of a direct flocculo-prepositus projection in the cat. It is suggested that this pathway could be responsible for mediating information about eye position and velocity to Ph neurons.
    Materialart: Digitale Medien
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 134 (1983), S. 295-298 
    ISSN: 1432-072X
    Schlagwort(e): Actinomycetes ; Streptomyces thermoviolaceus ; Sporogenesis ; Spore ornamentation ; Cupular knobs ; Sheath ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The sporogenesis of aerial spores in Streptomyces thermoviolaceus corresponded to a common sporulation type in the genus. The sporulation septum was composed of an outer ring-shaped constriction wall and an inner interspace septum arising by the inwards growth of a double annulus. In mature spores the wall was composed of two layers, the outer one was part of the parent hyphal wall and septum material, the inner one was formed de novo. The spore chains were enclosed by the thin breakable sheath containing small rod-like elements. The ornamentation in the form of knobs, which were a characteristic feature of the species originated from the sheath. The knobs were hemispherical particles with an inner electron dense core and an outer electron transparent shell. The term “cupular knobs” was suggested for this type of tuberculate ornamentation. Frequently, the knobs became detached from the surface in which case the inner core separated easily from the shell.
    Materialart: Digitale Medien
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Archives of gynecology and obstetrics 233 (1983), S. 295-308 
    ISSN: 1432-0711
    Schlagwort(e): Sertoli-Leydig cell tumor ; Pregnancy ; Catheterization ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary An extremely rare case of a conception occurring in a 26-year-old patient with a small virilizing Sertoli-Leydig cell tumor (diameter: 0.6 cm), bilateral polycystic ovaries and non-tumorous adrenal hyperandrogenism is presented. Prepregnancy findings included hirsutism, clitoromegaly, secondary amenorrhea, and elevated peripheral plasma testosterone (T; 5.7 ng/ml). Extensive basal steroid screening, dynamic function tests, conventional radiologic procedures, selective glandular vein catheterization, and laparoscopy failed to localize unequivocally the source of androgen excess, but suggested bilateral adrenal involvement. The patient conceived during the diagnostic work-up; peripheral T levels increased to 12.1 ng/ml within the first trimester. An exploratory laparotomy with left adrenalectomy, right adrenal biopsy and left ovarian wedge resection revealed an incompletely removed Sertoli-Leydig cell tumor, but normal adrenal histology. The pregnancy was terminated, a left oophorectomy and right ovarian wedge resection were performed at 14 weeks' gestation. Subsequently, peripheral androgens returned to normal, regular menses resumed, and hirsutism disappeared. Three years later the patient delivered a healthy female infant.
    Materialart: Digitale Medien
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 192 (1983), S. 171-178 
    ISSN: 1432-041X
    Schlagwort(e): Differentiation ; Digestive tract ; Endoderm ; Organ culture ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The self-differentiation potency of the endoderm of the chick embryo was investigated mainly by transmission electron microscopy. Endodermal fragments isolated from 4- to 6-day stomach or small intestine were cultured in the absence of mesenchyme and were able to differentiate in vitro into organ-specific epithelia. Endodermal fragments isolated from the stomach region differentiated into a pseudo-stratified epithelium with periodic acid Schiff-positive mucous granules in the apical cytoplasm, while those from the small intestinal region differentiated into a simple columnar epithelium with a striated border which was positive in alkaline phosphatase activity. These features are comparable with those of the mucous secretory epithelium of the normal embryonic stomach and the absorptive epithelium of normal embryonic small intestine, respectively. Next, the self-differentiation potencies were investigated of the upper and lower layers of the blastoderms, at stages 1–5 of Hamburger and Hamilton (H. and H.). Both stomach-type and small-intestine-type epithelia developed only when fragments of the lower layer isolated from the blastoderms older than stage 3 of H. and H. were cultured, suggesting that cells possessing the potency to differentiate into the stomach- and small-intestine-type epithelia exist in the definitive endoderm at the beginning of its formation.
    Materialart: Digitale Medien
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Journal of cancer research and clinical oncology 105 (1983), S. 106-108 
    ISSN: 1432-1335
    Schlagwort(e): Human T-cell line ; Type-C virus particles ; Adult T-cell leukemia ; Immunoagglutination ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A T-cell line, MT-2, derived from human cord blood lymphocytes by cocultivation with adult T-cell leukemia (ATL) cells is a continuous producer of type-C virus particles. Electron microscopy of MT-2 cells cultured for 1–3 weeks in medium containing 10% ATL patients' sera revealed agglutination of type-C virus particles within the electron-dense deposits in the extracellular spaces. No such agglutination occurred in control cultures supplemented with normal human or fetal calf serum. These results provide direct evidence for the specific reactivity of ATL patients' sera with type-C virus particles in the MT-2 cell line at the ultrastructural level.
    Materialart: Digitale Medien
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  • 27
    ISSN: 1432-0533
    Schlagwort(e): Ultrastructure ; Fetus ; Nervous system ; GM1-gangliosidosis type 1
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The nervous system of a 22-week-old fetus with GM1-gangliosidosis type 1 was studied by electron microscopy. The tissues thus examined were the cerebral cortex at the parietal region, the cerebellum, the thoracic spinal cord, the Auerbach's myenteric plexus in the large intestine and the radial nerve fibers. In the cerebral cortex, membrane-bound vacuoles, which occasionally contained stacks of fine fibrils, were observed in the large young neurons in the deeper part of the cortical plate. The neurons in the other part of the cerebral cortex carried no storage materials. In the cerebellum, the membrane-bound vacuoles with stacks of fine fibrils were seen only in the Purkinje cells. The neurons in the spinal cord also contained several zebra-like bodies and the above membrane-bound vacuoles. As for the peripheral nervous system (PNS), neurons in the Auerbach's myenteric plexus carried membranous cytoplasmic bodies and zebra-like bodies. Some of the axons in the radial nerve fibers also contained a lot of pleomorphic electron-dense bodies and a few membranous cytoplasmic ones. These results show that the accumulation of storage materials is started in the large neurons which are produced in the early stage of neurogenesis in the central nervous system (CNS). Additionally, the observed membrane-bound vacuoles are considered to be structures which occur before the membranous cytoplasmic bodies and/or the zebra-like bodies. It is also elucidated that the PNS is affected earlier than the cerebral and cerebellar cortices and thoracic spinal cord.
    Materialart: Digitale Medien
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  • 28
    ISSN: 1432-0533
    Schlagwort(e): Ischemia ; Brain ; Hippocampus ; Synapses ; Ultrastructure ; Morphometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A 10-min long ischemic insult followed by up to 60-min survival results in several changes of the synaptic ultrastructure in the hippocampal CA-1 region. The alternations consist of gradual change of synaptic curvature from neutral to positive, cleavage and decrease in thickness of the postsynaptic densities and, in the case of many terminals, wrinkling of their profiles. The most striking form of damage are membrane discontinuities which begin to appear in very small numbers after 20 min of blood reflow and become much more pronounced after 60 min. The development of those modifications seems to be time-related, whereas decrease in the number of synaptic vesicles, as shown by the morphometric analysis, occurs after 10 min and does not progress any further after 20 and 60 min. This decrease is most pronounced in the immediate vicinity of the presynaptic membrane. Although the observed signs of ultrastructural alternations of synapses in the postischemic period appear to conform to the general pattern of synaptic degeneration observed under other conditions, the severity of ischemia is underlined with the rate at which those changes develop, thus pointing toward grossly disturbed metabolism of postischemic neurons. Recently, a number of theories have been advanced, discussing significance of ischemic destruction of membrane phospholipids. These theories are discussed in the context of membrane discontinuities reported in this investigation.
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  • 29
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 61 (1983), S. 275-282 
    ISSN: 1432-0533
    Schlagwort(e): Neurofibromatosis ; Cell culture ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Skin fibroblasts and tumor cells were cultured from four patients with peripheral von Recklinghausen's neurofibromatosis (NF). The cell type enriched in culture from the tumors carried the fibroblastic Thy 1.1. cell surface antigen and produced fibronectin, like fibroblasts from skin of NF-patients or from control persons. In electron micrographs the NF tumor and NF skin cells were similar to the control skin fibroblasts; elongated in shape, contained tubular mitochondria, variable amounts of granular endoplasmic reticulum, numerous lysosomal inclusion bodies and collections of 5 nm filaments. Trypsinized cells were fractionated with centrifugation in a Percoll density gradient. All cell lines produced only one sharp band of viable cells at the buoyant density of 1.03. Compared with the NF skin or control skin fibroblasts the NF tumor cells, however, produced a less well organized peri-and extracellular matrix estimated from fibronectin fluorescence. The nuclear sizes were measured from photographs of the cultures. The nuclei of all four tumor cell lines were larger than those of the skin fibroblasts of the corresponding patients. Neurofibromatosis tumor cells thus resemble skin fibroblasts in their density and in some ultrastructural properties but are different in their growth pattern and synthetic functions.
    Materialart: Digitale Medien
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  • 30
    ISSN: 1432-0533
    Schlagwort(e): β-Galactosidase and neuraminidase deficiency ; Neuronal inclusion bodies ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary An autopsy case of a Japanese male with familial β-galactosidase and neuraminidase deficiency is reported. The clinical picture was characterized by adult onset, a gargoyle-like face, cerebellar ataxia, myoclonus, convulsions, retinal degeneration and cortical blindness. Histopathologically, most neurons seemed to have become degenerated in the whole cerebral cortex. Moreover, the calcarine cortex appeared spongy with depopulation of nerve cells. Stuffed neurons or neuronal storage changes were found throughout the brain, especially in the motor nuclei of the spinal cord and brain stem. The inclusions in the stuffed neurons revealed various profiles on the electron microscope. They were composed of membranous lamellar and/or multilamellar structures, often accompanying vacuoles and reminiscent of lipofuscin-like profiles.
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  • 31
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 62 (1983), S. 1-14 
    ISSN: 1432-0533
    Schlagwort(e): Pituitary adenomas ; Immunohistology ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary An analysis is presented of the immunohistological and ultrastructural features in a series of 118 surgically removed pituitary adenomas all of which were studied immunohistologically using antisera to growth hormone (GH), prolactin (PRL) ACTH, βFSH, βLH and βTSH, and 75 of which were studied ultrastructurally. Results were analysed according to the mode of presentation of patients. Forty-one (35%) of the tumours were from patients with acromegaly or gigantism, ten (9%) from patients with Cushing's syndrome or Nelson's syndrome, 19 (16%) from patients with clinical features associated with hyperprolactinaemia and 48 (40%) from patients with space occupying lesions which appeared clinically to be overtly endocrinologically functionless. By light microscopy, using the immunoperoxidase (PAP) technique, immunoreactive GH was demonstrated in all the tumours from patients with acromegaly or gigantism, immunoreactive ACTH in all tumours from patients with Cushing's syndrome or Nelson's syndrome and immunoreactive PRL in 95% of tumours associated with effects of hyperprolactinaemia. Forty-five percent of the tumours from acromegalic patients contained some PRL-positive cells as well as GH-positive cells. Among the tumours which appeared clinically to be endocrinologically functionless were three tumours (from males) uniformly stained for immunoreactive PRL. Of the remainder, 60% were negative for immunoreactive hormones and 40% contained small numbers of cells which were positive for a variety of immunoreactive hormones. ACTH-cell and PRL-cell tumours had ultrastructural features as described in previous studies. Fifty percent of GH-cell tumours examined at the EM level contained fibrous bodies, while in the remainder these structures were not identified. Tumours with fibrous bodies were more likely to contain PRL as well as GH with immunoperoxidase. All tumours that were endocrinologically functionless and which were examined at the EM level contained secretory granules. Oncocytic change was common in these tumours. No ultrastructural differences were observed between those which contained immunoreactive hormones by light microscopy and those which did not.
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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 62 (1983), S. 31-40 
    ISSN: 1432-0533
    Schlagwort(e): Human pinealomas ; Ultrastructure ; Specific markers ; Pinealocyte
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary An ultrastructural study of four pinealomas was carried out to precise eventual specific markers. Dark and clear cells joined with zonulae adherents, extensive and pleiomorphous processes, a complex vacuolar system, and characteristic organelles (lysosome-like structures, clear and dense-core vesicles, vesicle-crowned rodlets and related structures, microtubular sheaves and centriolar derivatives, membranous whorls, fibrous bodies, microtubules, heterogeneous cytoplasmic inclusions) offered a typical pattern. No correlation could be made between the histological and ultrastructural features. The authors stress the ultrastructural similarities between the human tumor cells and the mammalian pineal cells. Pinealomas appeared as a morphological entity distinct from neuronal and astrocytic tumors.
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  • 33
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 71 (1983), S. 147-153 
    ISSN: 1573-5036
    Schlagwort(e): Cortex ; Endodermis ; Picea sitchensis ; Tilia cordata ; Transfer cells ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The endodermis of bothTilia cordata andPicae citchensis progressess through 3 characteristic phases of development. These developments are delayed somewhat in the xylem pole endodermis ofT. cordata, while inP. sitchensis 3–5 passage cells are found. The cortex ofT. cordata is characterised by very thick walls, while that ofP. sitchensis is characterised by a thick walled layer just outside the endodermis and by 2–3 outer layers of transfer cells.
    Materialart: Digitale Medien
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  • 34
    ISSN: 1434-0879
    Schlagwort(e): Human bladder tumour ; Non-tumorous human bladder mucosa ; Hyperthermic vesical irrigation ; Bleomycin ; Ultrastructure ; Scanning electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Bladder tumours and non-tumorous bladder mucosa were studied by scanning and transmission electron microscopy in seven patients who had undergone hyperthermic vesical irrigation with bleomycin. The treatment induced sloughing of the outermost tumour cells, an increase of blebs and a decrease of cytoplasmic processes of the deeply located tumour cells as well as cellular degeneration. Although less severe, non-tumorous mucosa showed similar changes. Microvilli also appeared on the superficial cells of non-tumorous mucosa after the treatment. This treatment is effective by inducing cell degeneration and desquamation but not selective to the bladder tumour.
    Materialart: Digitale Medien
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  • 35
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 228 (1983), S. 573-585 
    ISSN: 1432-0878
    Schlagwort(e): Satellite cells ; Muscle fibres ; Anura ; Metamorphosis ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The incidence and the ultrastructure of the satellite cells associated with red and white muscle fibres of the anuran (Rana japonica) tadpole tail were examined in three stages (hindlimb-bud, prometamorphic, and climax) during metamorphosis. In these three stages the satellite cells are found more frequently in the red fibres than in the white fibres. As metamorphosis proceeds, the incidence of the satellite cells decreases in both red and white fibres. The satellite cells in the hindlimb-bud stage have abundant cytoplasm rich in organells. Cisternae of rough endoplasmic reticulum are often dilated. The intercellular space between the satellite cell and the muscle fibre is narrow and relatively constant (15–25 nm). Some satellite cells appear to be in the process of fusion with the muscle fibre. Cytoplasmic volume and organellar content are gradually reduced during metamorphosis. In the prometamorphic and climax stages, the intercellular space is in general gradually extended. It often exceeds 0.5 μm, and usually contains the basal lamina and fibrous materials. Some satellite cells have cytoplasmic processes that project into the interstitial space through a gap in the basal lamina.
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 230 (1983), S. 77-94 
    ISSN: 1432-0878
    Schlagwort(e): Ascidian larva ; Embryology ; Myogenesis ; Somatic striated (skeletal) muscle ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The larval muscle cells of Diplosoma macdonaldi contain subcortical and medullary myofibrils which are invested by fenestrated sheets of the sarcoplasmic reticulum. Cisternae of the sarcoplasmic reticulum are coupled with tubular invaginations of the sarcolemma. To appreciate better such uncommon features of cellular organization, six embryonic stages were selected for an ultrastructural study of myogenesis. The proliferative, synthetic, and elaborative phases of myogenesis were represented by embryos ranging from neurulae to prehatching larvae. The contractile apparatus originates during the synthetic phase of myogenesis, when thick and thin myofilaments appear in the cortical sarcoplasm at the epidermal and notochordal poles of the cell. The myofilaments promptly aggregate into unstriated fascicles, and the fascicles unite in series to establish the rudimentary myofibrils. All major sarcomeric bands, except the Z-lines, are evident along the myofibrils. Cisternae of the sarcoplasmic reticulum form peripheral couplings with the overlying sarcolemma, and they also form interior couplings with sarcolemmal invaginations from the ends of the cell. The interior couplings localize over the I-bands of the myofibrils. In the elaborative phase of myogenesis, mitochondria invade the cortical sarcoplasm, and the contractile apparatus passively shifts to the subcortex and medulla of the cell. Relocation of the myofibrils coincides with the disappearance of all peripheral couplings. Cisternae of the sarcoplasmic reticulum anastomose around the myofibrils, creating the fenestrated sheets that extend between sarcomeres. As Z-lines begin to bisect the I-bands, the perifibrillar cisternae become confluent with the cisternae in the precocious interior couplings.
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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 230 (1983), S. 105-111 
    ISSN: 1432-0878
    Schlagwort(e): Heart ; Purkinje fibre ; Innervation ; Ultrastructure ; Scanning electron microscopy ; Transmission electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary An observation of intimate nerve-Purkinje fibre associations in false tendons of sheep heart is reported. Nerve bundles were observed in deep clefts of Purkinje fibres, in channels running between coupled Purkinje cells and embedded within Purkinje cells, as well as in the outer connective tissue sheath. Most nerve terminals in these areas were filled with small clear vesicles and a few large dense-cored vesicles. Only a few axons with many small dense-cored vesicles were observed. Intimate associations (separation, 60 to 90 nm) between the Purkinje cell and nerve varicosity were observed in the deep clefts. Similar close appositions were also present where nerves were embedded in Purkinje cells. In these cases the Purkinje cell enclosing the nerve bundle formed intercellular junctions with its own sarcolemma. Elaborate sarcolemmal folds with multi-vesicular bodies were also frequently observed near nerve bundles and varicosities. The identity of the transmitter is unknown although the nerves forming intimate associations with Purkinje cells have a morphology typical of cholinergic nerves.
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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 230 (1983), S. 205-218 
    ISSN: 1432-0878
    Schlagwort(e): Kidney ; Glomerulus ; Ultrastructure ; Teleosts ; Seawater adaptation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The epithelial ultrastructure of the glomerulus of fresh- and sea-water adapted rainbow trout, Salmo gairdneri was examined by scanning and transmission electron microscopy after in vivo-perfusion fixation. Adaptation to seawater for a period of up to 9 weeks was not associated with a change in glomerular size, although after one year in seawater both glomeruli and their capsules were significantly smaller than the glomeruli of freshwater adapted fish. In freshwater adapted trout the epithelial ultrastructure conformed to the general vertebrate pattern, with rounded podocytes, well-defined primary processes and interdigitating pedicels. Adaptation to seawater was associated with a marked increase in the frequency of cytoplasmic microprojections. In many glomeruli there was a flattening of the podocytes, broadening of the primary processes, and areas of closely-packed pedicels were common. These observations are discussed in the light of previous studies on the mammalian kidney and the changes of single nephron function known to be associated with adaptation of trout to increased environmental salinities.
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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 230 (1983), S. 587-603 
    ISSN: 1432-0878
    Schlagwort(e): Pituitary ; Tammar wallaby ; Marsupial ; Neonate ; Ultrastructure ; Immunohistochemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The pars distalis of pouch-young wallabies (Macropus eugenii) aged 1 to 50 days was studied by means of light-microscopic immunohistochemistry and electron microscopy. In the pars distalis of these pouch-young presumptive somatotrops, which constituted up to 70% of the gland, and nongranulated cells were the most numerous cell types. Small numbers (together representing less than 30% of the pars distalis) of immunoreactive mammotrops, thyrotrops, gonadotrops and corticotrops were also found. The presumptive mammotrops, gonadotrops and thyrotrops increased in number and apparent activity between 1 and 50 days postpartum. Presumptive corticotrop cells in 25 to 30 day-old animals were relatively most numerous, and apparently more active than at any other stage of pouch life; these cells decreased in apparent activity and relative number in older animals. The changes in number and activity of cell types in the pars distalis correlated well with major developmental events such as the onset of adrenal activity, the rapid growth phase in the first 100 days postpartum, and the generally low thyroid activity in pouch-young of less than 50 days of age.
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  • 40
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 230 (1983), S. 615-630 
    ISSN: 1432-0878
    Schlagwort(e): Epidermis ; Mouth mucosa ; Connective tissue ; Cell differentiation ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Specimens of buccal mucosa and ear skin were introduced into the uteri of isologous rats and the animals maintained under estrogen stimulation for ten weeks, whereupon the uteri were removed and processed for light- and electron-microscopic examination. The majority of implants were successful with the epithelium having migrated to replace the adjacent uterine epithelium. Epidermis and oral epithelium growing on its own connective tissue in the uterus showed a normal pattern of histodifferentiation, including the formation of a thickened keratinized surface and appendages such as hair and sebaceous glands. Ultrastructurally, maturation was similar to that of normal tissue. Epidermis growing on uterine connective tissue did not form appendages but the ultrastructural pattern of cytodifferentiation was similar to control tissue. Buccal epithelium on the uterine stroma was markedly altered in its pattern of maturation, the epithelium appearing thinner than usual and showing a pattern of maturation resembling that of non-keratinization. These results suggest that normal histodifferentiation in epidermis and oral epithelium requires the presence of the appropriate connective tissue; in its absence epidermis has an intrinsic capacity for more or less normal cytodifferentiation but this is lacking in the buccal epithelium.
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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 230 (1983), S. 661-670 
    ISSN: 1432-0878
    Schlagwort(e): Preimplantation embryos ; Mouse ; Ultrastructure ; Morphometric analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary During cleavage, both qualitative and quantitative morphologic characters of mouse ova change. Up to the 8-cell stage, the volume density of mitochondria remains nearly the same although it increases during early and late blastocyst stages. While a rise of the volume fraction of granular endoplasmic reticulum is noticed during cleavage, the volume density of agranular endoplasmic reticulum diminishes gradually from the 1-cell stage onwards. An increase in the volume fraction of autophagic vacuoles is found, the maximum being reached in early blastocysts. The volume fraction of crystalloid inclusions slightly increases after the 4-cell stage, but this increase is statistically insignificant. The volume density of filamentous material (plaques) conspicuously decreases in all studied embryos from the beginning of cleavage. Starting with the 2-cell stage, the volume fraction of lipid droplets remains practically unchanged. No differences in volume densities of the Golgi apparatus, multivesicular and residual bodies, and large cytoplasmic vesicles with medium electron-dense content are found between the respective cleavage stages.
    Materialart: Digitale Medien
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  • 42
    ISSN: 1432-0878
    Schlagwort(e): Babesia ; Tick ; Sporogony ; Salivary gland ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Tick larvae were permitted to feed on infected hamsters and then allowed to molt. Nymphs were examined just prior to feeding on uninfected hamsters or at timed intervals thereafter. Invasion of the salivary gland by B. microti occurs before feeding of the nymph begins, and development of the parasite is further stimulated by feeding. The sporoblast forms a massive multinucleated meshwork which ramifies throughout the large host cell. No separation of the meshwork into multiple subdivisions, termed “cytomeres” by other workers, has been detected. Instead the specialized organelles characteristic of sporozoites, namely micronemes, rhoptries, and segments of double membrane appear in the meshwork itself and gradually become organized into sporozoite anlagen which protrude from its surface. At the same time the meshwork shortens and thickens giving rise to large compact undifferentiated bodies whose surface is also studded with sporozoite anlagen. Sporozoites thus originate either from the meshwork or from the undifferentiated bodies. In either case large lobate nuclei send projections into the anlagen as they protrude from the surface of the sporoblast. In a final step the mature sporozoites arise by simultaneous nuclear and cytoplasmic divisions. There is no separate stage of schizogony and the process is one of true budding.
    Materialart: Digitale Medien
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  • 43
    ISSN: 1432-0878
    Schlagwort(e): Adrenal zona glomerulosa ; Ultrastructure ; Sodium depletion ; Sodium loading ; Sheep
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The effects of alterations in sodium status upon the morphology of the adrenal zona glomerulosa in sheep have been examined qualitatively and quantitatively, using lightand electron microscopy, and correlated with functionally related biochemical data. With severe sodium depletion induced by parotid-cannula drainage, there was mitotic activity throughout the zona glomerulosa, and glandular cells showed striking ultrastructural changes. These changes particularly affected mitochondria, which were enlarged, rounded and showed replacement of their normal lamelliform cristae by thin elongated cristal elements and bundles of tubular “rod-like” structures. Quantitative morphometric studies showed an increase in the volumes of zona glomerulosa cells, nuclei, mitochondria, smooth and granular endoplasmic reticulum, and Golgi profiles. In contrast, with dietary sodium loading, zona glomerulosa cells appeared shrunken and showed cytoplasmic lipid accumulation; mitochondria and other organelles were not significantly altered. The correlation of the ultrastructural cytological alterations in zona glomerulosa cells in sodium-depleted sheep with raised blood aldosterone levels suggests that such morphologic changes reflect a heightened capacity of these cells for aldosterone biosynthesis and secretion. These changes may also account for the increased sensitivity of the zona glomerulosa to aldosterone-producing stimuli during sodium deficiency.
    Materialart: Digitale Medien
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  • 44
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 231 (1983), S. 663-674 
    ISSN: 1432-0878
    Schlagwort(e): Ciliary tuft ; Pallil tentacles ; Patella vulgata ; Sensory ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The structure and ultrastructure of ciliary tufts on the pallil tentacles of the limpet Patella vulgata (L.) are described. The tip of each tentacle is covered by a dense crown of tufts and additional tufts can be seen scattered evenly across the surface of each tentacle. The cilia are nonmotile and nerve fibres run from the base of the ciliated cells suggesting a sensory function. Comparisons are made with ciliary tufts found in a Pacific species of limpet, Acmaea scutum, and other molluscan sensory structures.
    Materialart: Digitale Medien
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  • 45
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 233 (1983), S. 59-67 
    ISSN: 1432-0878
    Schlagwort(e): Pineal gland ; Synaptic ribbon ; Melatonin ; Ultrastructure ; Chinese hamster (Cricetulus griseus)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The effects of melatonin on synaptic ribbons (SR) in pinealocytes of the Chinese hamster (Cricetulus griseus) were examined. SR were classified into types 1, 2 and 3, which appear as rods, round or irregular bodies and ring-shaped structures, respectively; a synaptic ribbon index (SR index) was determined for the three types. Administration of two doses of 1.5 mg/kg melatonin at noon and 3 p.m. causes an increase in the type-1 and type-2 SR indices 3 h after the second injection in hamsters kept under alternating light and dark conditions (lights on from 7 a.m. to 7 p.m.). Likewise, in animals that are exposed to extended light for 6 h and receive two doses of melatonin at 7 p.m. and 10 p.m., an increase in the type-1 and type-2 SR indices occurs 3 h after the second injection. The increase in the type-2 SR index induced by melatonin administration to hamsters exposed to extended light is greater than the increase in the type-1 SR index under the same experimental conditions. Type-2 SR index, but not type-1 SR index, increases following bilateral superior cervical ganglionectomy. An increase in type-1 and type-2 SR indices occurs at 6 p.m. in ganglionectomized animals administered two doses of melatonin 6 h (noon) and 3 h (3 p.m.) before the time of sacrifice. No significant change is observed in type-3 SR index in animals subjected to any of the above treatments. The results indicate that exogenous melatonin may act directly on pinealocytes of the Chinese hamster to cause an increase in size and/or number of the type-1 and type-2 SR. Type 3-SR may have a role different from that of type-1 and type-2 SR; type-1 and type-2 SR may be functionally related.
    Materialart: Digitale Medien
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  • 46
    ISSN: 1432-0878
    Schlagwort(e): Myocardium ; Ultrastructure ; Myocardial biopsy ; Morphometry ; Papillary muscle
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The papillary muscle of the cat heart's right ventricle has not been studied previously with quantitative ultrastructural techniques despite its wide use for functional studies. This tissue was perfusion-fixed, processed for electron microscopy, and morphometric techniques were used to assess the ultrastructural characteristics of the papillary muscle as well as the working myocardial cells. The results of this study were that 73.5% of the papillary muscle was composed of muscle cells, 9.7% of blood vessels, and the remainder of interstitial connective tissue. In the muscle cell the volume fraction of mitochondria was 17.3%, that of myofibrils was 49.8%, and that of the nucleus was 2.0%. The mitochondria to myofibrils ratio was 0.36 and the surface to volume ratio was 0.309. In a quantitative ultrastructural comparison of perfusion and immersion fixed tissue it was found that significant differences in the volume density of the blood vessel lumen existed between the two groups. In addition, there were significant differences in the volume fraction of mitochondria and nucleus between perfusion-fixed and immersion-fixed muscle cells. A concurrent significant decrease between the two groups was also found for the ratio of mitochondria to myofibrils. The perfusion-fixed tissue can be considered to provide only normal baseline data for the papillary muscle of the right ventricle. These data are important as they can be used in future structure-function studies on normal and pathological heart tissue.
    Materialart: Digitale Medien
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  • 47
    ISSN: 1432-0878
    Schlagwort(e): Corpus luteum ; Ultrastructure ; Secretory granules ; Hormones ; Quantitative study
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The granulosa luteal cells of the sheep corpus luteum secrete their hormonal products by exocytosis of granules. Electron micrographs of randomly selected granulosa cells from nine corpora lutea at day 10 of the oestrous cycle were examined to obtain the cellular density of these granules. From the area of the cell, calculated using an x -y digitiser, and the number of granules observed, the number of intracellular secretory granules per μm3 of luteal cell cytoplasm was calculated. There was a large variation in the number of granules per cell within the same corpus luteum and between corpora lutea taken at the same stage of the cycle. The number of intracellular granules in nine corpora lutea varied from 2.12±1.05 granules per μm3 (x, SD, n = 30) cells to 0.36±0.18 granules per μm3 ( x, SD, n = 26). These morphological data suggest that the variation in granule synthesis in individual cells may contribute to the variation in hormone content of corpora lutea at the same stage of the cycle, and the episodic release of hormone into the plasma.
    Materialart: Digitale Medien
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  • 48
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 231 (1983), S. 103-115 
    ISSN: 1432-0878
    Schlagwort(e): Synapses ; Ultrastructure ; Crustacean ; Neuromuscular synapse ; Synaptic differentiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Synaptic terminals on branches of an excitatory motor axon in a spider crab (Hyas areneas) were examined by electron microscopy to determine whether differences in size, structure, and number of synapses could be correlated with differences in transmitter release. Terminals releasing relatively large amounts of transmitter during low frequencies of nerve impulses (“high-output” terminals) had larger synapses, more prominent presynaptic dense bodies (active zones), and fewer synapses per unit length than terminals releasing relatively small amounts of transmitter (“low-output” terminals). Neither the difference in synaptic area, nor the quantitative differences in the active zones, were sufficient in themselves to explain the difference in synaptic efficacy, and it is postulated that a non-linear relationship may exist between structural features of the synapse and release of transmitter by a nerve impulse, and that differences other than those apparent from the ultrastructure could be involved. Greater facilitation at low-output terminals with high frequencies of nerve impulses may be due to greater reserves of “immediately available” transmitter, and to recruitment or activation of more individual synaptic contacts.
    Materialart: Digitale Medien
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  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 232 (1983), S. 445-455 
    ISSN: 1432-0878
    Schlagwort(e): Avian thymus ; Intrathymic erythropoiesis ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Although previously described in other avian species, intrathymic erythropoiesis is a remarkable feature of the thymus of Sturnus unicolor. In discrete stages of the life cycle of this species, erythroblasts and mature erythrocytes occupy large areas of the thymic cortex and cortico-medullary border. Simultaneously, degenerated thymocytes and epithelial-reticular cells occur in the same areas. The relationship between intrathymic erythropoiesis, degeneration of cortical lymphocytes and epithelial-reticular cells, and macrophage activity is discussed and related to a possible functional role of sex hormones in this phenomenon.
    Materialart: Digitale Medien
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  • 50
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 233 (1983), S. 629-638 
    ISSN: 1432-0878
    Schlagwort(e): Ciliary process ; Cultured explant ; Epithelial cells ; Ultrastructure ; Bovine and rabbit eyes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The ultrastructural characteristics of ciliary epithelium from bovine, pigmented rabbit, and fetal albino rabbit were studied in cultured explants. The tips of ciliary processes were cultured in plastic dishes with Dulbecco Modified Eagle Medium (DMEM) containing 5% fetal bovine serum. More than half of the expiants adhered to the plastic culture dish, and epithelial cells spread as monolayers within a few days. Initially the explant contains two layers, the outer (nonpigmented cells) and the inner (pigmented cells). Later the explant exhibits three layers: 1) outermost lightly pigmented flattened cells, 2) an outer layer of nonpigmented cells, and 3) an inner layer of densely pigmented cuboidal cells. The cells of the outermost layer are continuous with the cells of the inner layer. A narrow space lies between the outermost layer and the outer layer. The columnar cells in the outer layer contain well developed organelles but no pigment granules; they possess a basement membrane, lateral interdigitations, and junctional complexes near their apices. Numerous focal junctions and some ciliary channel-like structures were detected between the columnar cells of the outer layer and the cuboidal cells of the inner layer. The cuboidal cells of the inner layer are filled with pigment granules. These observations suggest that the columnar cells of the outer layer are nonpigmented epithelium, the cuboidal cells of the inner layer are pigmented epithelium, and the flatened cells in the outermost layer are derived from pigmented epithelium.
    Materialart: Digitale Medien
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  • 51
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A2 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 52
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 126-130 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Wear Resistance of Liner Material for Extruding Non-ferrous AlloysExtruding Al and its alloys Cu, brass, Cu-Ni alloys and Ni on account of variable working conditions (as temperature) different liner materials are used.Processing Al martensitic hot work steels are successful in application. Working up copper high temperature resistant and austenitic steels are additional in use.The high-temperature strength of these materials is well-known.Based on the investigation of the high-temperature wear this paper presents several new considerations.
    Notizen: Anforderungen an die Innenbüchsenwerkstoffe für das Strangpressen von Aluminiumlegierungen, Reinkupfer, Messing, Kupfer-Nickellegierungen und Reinnickel; Kriterien für die Stahlauswahl. Verschleißverhalten in Abhängigkeit von Werkstoffpaarung und Beanspruchungstemperatur; Warmfestigkeit von martensitischen Warmarbeitsstählen und hochwarmfesten Austeniten.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 53
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A45 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 54
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983) 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 55
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A52 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 56
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Siliciumnitrid: Gefüge, Eigenschaften und neue HerstellungsverfahrenAnhand der Korrelation zwischen einigen wichtigen Gefügeparametern und verschiedenen mechanischen, thermischen und thermomechanischen Eigenschaften von heißgepreßtem und reaktionsgesintertem Siliciumnitrid wird die Forderung nach einer weiteren Verbesserung der Eigenschaften und nach einer ökonomischeren Herstellung von Siliciumnitrid durch Anwendung neuer Verfahren aufgezeigt. Die Aussichten und Probleme bei den verschiedenen neuen Verfahren, dem Sintern von verdichteten Si3N4 - Pulverkörpern, dem Nachsintern von reaktionsgesintertem Siliciumnitrid und den verschiedenen Methoden des heißisostatischen Pressens, werden diskutiert.Die Arbeit ist in 2 Teile unterteilt:Teil I: Einfluß des Gefüges auf die mechanischen, thermischen und thermomechanischen Eigenschaften von Siliciumnitrid.Teil II: Neue Herstellungsverfahren von Siliciumnitrid.In Teil I wird der Zusammenhang zwischen Gefüge und verschiedenen mechanischen, thermischen und thermomechanischen Eigenschaften von heißgepreßtem und reaktionsgesintertem Siliciumnitrid diskutiert, wie Bruchfestigkeit, Temperaturleitfähigkeit und Thermoschockverhalten. Aufbauend auf dieser Korrelation werden die heutigen Grenzen von Siliciumnitrid für eine breitere Anwendung sowie die Möglichkeiten für eine Optimierung dieser Materialgruppe dargelegt. Diese Diskussion zeigt sehr deutlich, daß es notwendig ist, einige wichtige Eigenschaften weiter zu verbessern und neue Herstellungsverfahren zu entwickeln. In Teil II der Arbeit werden die Entwicklungsrichtungen dieser neuen Herstellungsverfahren für Siliciumnitrid aufgezeigt. Es wird ein Überblick über die in jüngster Zeit erzielten Fortschritte bei der Anwendung dieser Verfahren gegeben. Als Beispiel für ein neues Herstellungsverfahren werden Ergebnisse vom heißisostatischen Pressen von reaktionsgesintertem Siliciumnitrid diskutiert.
    Notizen: Based on the correlation of some essential microstructural parameters and various mechanical, thermal and thermo-mechanical properties of hot-pressed and reaction-bonded silicon nitride, the demand for further improving the properties of silicon nitride and for developing a more economical fabrication of silicon nitride by applying new processing techniques is indicated. Aspects and problem areas of various new techniques, such as sintering of Si3N4-powder compacts and post-sintering of reaction-bonded silicon nitride as well as the various routes of hot-isostatic pressing, are discussed. The paper is divided into two parts:Part I: Microstructural effects on mechanical, thermal and thermomechanical properties of silicon nitride.Part II: New processing techniques of silicon nitride.In part I the relationship between microstructure and various mechanical, thermal and thermo-mechanical properties of hot-pressed and reaction-bonded silicon nitride, such as fracture strength, thermal diffusivity and thermal shock resistance, is discussed. On the basis of this correlation today's limits of silicon nitride regarding a broader application, and the possibilities for optimizing this material group are outlined. This discussion demonstrates the necessity of further improving some important properties and of developing new processing techniques. In part II the development lines of these new techniques for silicon nitride processing are discussed and a survey is given of recent progresses in the use of those techniques. As an example of a new processing technique, results of hot-isostatic pressing of reaction-bonded silicon nitride are presented in more detail.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
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  • 57
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 37-41 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Long Term Creep Tests with HDPE Pipes under the Influence of Several FluidsThe results of long term creep tests with unwelded and welded HDPE pipes under the influence of several fluids are presented. It is shown that the resistance factors determined by the investigations of tubes are also valid for welded constructions, when the long term weld factors in DVS 2205, Blatt 1 are taken in consideration.
    Notizen: Es werden die Ergebnisse von Zeitstandinnendruckversuchen an ungeschweißten und geschweißten Rohren aus HDPE im Kontakt mit einigen chemischen Medien vorgestellt. Dabei zeigt sich, daß die an ungeschweißten Rohren ermittelten Resistenzfaktoren auch für geschweißte Bauteile gelten, wenn man die in Merkblatt DVS 2205 Blatt 1 angegebenen Langzeitschweißfaktoren berücksichtigt.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 58
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 41-44 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Weitere Überlegungen zur Entwicklung von Oberflächenfehlern bei stabilem WachstumAuf Grundlage einer früheren Arbeit [1] wird eine allgemeingültige Beziehung für die Entwicklung der Kontur von Oberflächenrissen angegeben. Für Zugbeanspruchung wird eine analytische Funktion hergeleitet, mit der auf einfache Weise Parameterstudien betrieben werden können. Für andere Lastfälle müssen dagegen weiterhin numerische Verfahren angewendet werden. Das Rißwachstumsverhalten von Oberflächenrissen wird diskutiert.
    Notizen: Based on results of a previous paper [1] a general formula for the development of the shape of surface cracks is presented. In case of tension an analytical solution is presented, which allows a very easy parameter study. For other loading conditions solutions can be obtained, using numerical calculations. The behaviour of surface crack growth development is discussed.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 59
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 57-57 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 60
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 72-72 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 61
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983) 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 62
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 85-90 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Investigations Into the Corrosion of Three Steels and one Nickel Alloy in Mono- and Trichloroacetic AcidThe corrosion resistance of three steels and one nickel alloy was investigated in aqueous and nonaqueous monochloroacetic acid and in nonaqueous trichloroacetic acid at various temperatures.There is no difference in the corrosion behaviour of the steels whereas the resistance of the nickel alloy is better in all cases by a factor 10. In aqueous monochloroacetic acid the corrosion attack is due to the hydrolytic formation of hydrochloric acid. Nonaqueous monochloroacetic acid behaves more corrosive than nonaqueous trichloroacetic acid.
    Notizen: Die Korrosion von drei Stählen und einer Nickellegierung wurde in wäßriger und wasserfreier Monochloressigsäure sowie wasserfreier Trichloressigsäure bei verschiedenen Temperaturen untersucht. In allen Korrosiosystemen verhalten sich die Stähle etwa gleich, die Nickellegierung wird etwa um den Faktor 10 geringer angegriffen.In wäßriger Monochloressigsäure wird die Korrosion durch hydrolytisch gebildete Salzsäure verursacht. In wasserfreiem Zustand ist Monochloressigsäure deutlich aggressiver als Trichloressigsäure.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 63
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 290-298 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Zusätzliches Material: 29 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 64
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983) 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 65
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A96 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
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  • 66
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 350-356 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Zusätzliches Material: 39 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 67
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 367-382 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Determination of Stress Intensity Factors from Isochromatics by means of a Multiparameter-Multipoint-MethodA multi-parameter-multiple-point method (VPVP-method) for determination of mode-1 stress intensity factors from isochromatic fringe patterns has been developed and tested in connection with practical examples. In particular the stress field behaviour in compact-tension specimens is thoroughly investigated where variable numbers of series coefficients in the stress field expansion and a variety of data-point combinations featuring remoted and close field influences has been utilized. Cracks approaching free specimen boundaries have been given special attention.
    Notizen: Eine Vielparameter-Vielpunkt-Methode (VPVP-Methode) zur Bestimmung von mode-1 Spannungsintensitätsfaktoren von Rissen aus Isochromatenbildern wird entwickelt und an praktischen Beispielen geprüft. Ihre Anwendungsmöglichkeit auf Kompaktzugproben wird untersucht, wobei unterschiedliche Koeffizientenanzahlen und Datenpunktkombinationen zur Bestimmung von Spannungsintensitätsfaktoren aus verschiedenen randnahen und entfernten Isochromatenbildern um die Rißspitze in einer CT-Probe verwendet werden.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
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  • 68
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983) 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 69
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A120 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 70
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A60 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 71
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A89 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 72
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 322-324 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 73
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A103 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 74
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 336-341 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Simple Mechanical Models and Constitutive Equations with Regard to the Internal Damaging in Uniaxial Tension and CreepA modification of the Maxwell-Thomson equation for the standard solid of the linear theory of viscoelasticity is presented taking into account the internal damaging. The status of the modified constitutive equations are discussed in the frame of a more general theory. These equations describe the mechanical behaviour of materials in the tension test, for example beyond the yield stress, and in the creep test, for example with registration of all creep phases. The considerations presented in this paper can be generalized for all linear and nonlinear models or constitutive equations respectively.
    Notizen: Die Maxwell-Thomson-Gleichung des Standardkörpers der linearen Viskoelastizitätstheorie wird durch formale Berücksichtigung der Werkstoffschädigung modifiziert. Die Stellung der damit gegebenen einfachen mechanischen Zustandsgleichungen im Rahmen allgemeiner Beziehungen wird erörtert. Die aufgestellten Gleichungen beschreiben das mechanische Verhalten der Werkstoffe im Zugversuch, z. B. von Polypropylen über den Streckspannungsbereich hinaus, und im Zeitstandversuch, z.B. mit Erfassung aller Kriechstadien. Die dargestellten Überlegungen lassen sich auf alle linearen und nichtlinearen Modelle bzw. Zustandsgleichungen übertragen.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 75
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A112 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 76
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 77
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A66 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 78
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983) 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 79
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 253-257 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Gaslegieren mittels LaseraufheizungStähle lassen sich durch eine Laser-Wärmebehandlung härten. Eine Änderung der Oberflächenzusammensetzung bewirkt eine Erhöhung der Härtbarkeit. Indem die Laserbehandlung in einer geeigneten Atmosphäre durchgeführt wird, kann die Zusammensetzung während des Härtevorgangs simultan verändert werden. Dies wird an zwei Stählen in verschiedenen Atmosphären Argon, Luft, Stickstoff, CO2 und Acetylen gezeigt.
    Notizen: Laser heat treatment can be used to harden steel. By changing the surface composition the hardenability can be increased. The surface composition can be changed most simply by carrying out the Laser treatment in an appropriate atmosphere. This is demonstrated by variously treating two steels in argon, air, nitrogen, CO2 and acetylene.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 80
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 264-271 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Theoretical Considerations on the Solidification Behaviour of Rapidly Quenched MeltsThe rapid heating, cooling and solidification processes on laser surface melting are calculated. The influence of the laser operating parameters e.g. beam energy density, melting speed and the resultant depth of melt on the solidification parameters cooling rate, solidification rate and temperature gradient is shown. By combining the cooling curves and TTT (CT) curves an attempt can be made to predict the resulting grain size. The use of the programmes is demonstrated for other quenching methods e.g. melt spinning, powder atomizing.
    Notizen: In der vorliegenden Arbeit werden die beim Laserumschmelzen ablaufenden schnellen Aufheiz-, Abkühl- und Erstarrungsvorgänge berechnet. Es wird gezeigt, welchen Einfluß die Laserparameter Leistungsdichte, Vorschubgeschwindigkeit und Einschmelztiefe auf die für die Erstarrung relevanten Größen Abschreckgeschwindigkeit, Erstarrungsgeschwindigkeit und Temperaturgradient haben. Durch Kombination der Abkühlkurven mit TTT-Kurven (CT-Kurven) wird versucht, die entstehende mittlere Korngröße vorherzusagen. Beispielhaft wird die Übertragbarkeit der verwendeten Rechenprogramme auf andere Abschreckmethoden (Melt-Spinning, Powder-Atomizing) gezeigt.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
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  • 81
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 278-283 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: ARALL (Aramid Fibre Reinforced Aluminum Laminate)-A New Fatigue Resistant Hybrid CompositeHigh fuel expenses and the tendency to build larger aircrafts are two main factors forcing the aircraft engineers to develop structures which allow for higher design stress levels. Higher design stress levels require an increasing concern with the fatigue behavior of the structure. One way to solve the problem is to develop new high strength fatigue resistant materials. In this paper a material of this type is presented: ARALL, an aramid fibre reinforced aluminum laminate. This hybrid material consists of thin sheets of a high strength aluminum alloy which are bonded together. Into the bond-line thin layers of aramid fibres are embedded.As soon as fatigue cracks are initiated in the metallic part of the hybrid composite material during the fatigue loading, the strong and fatigue insensitive aramid fibres remain unbroken behind the propagating crack. They hinder the crack opening and reduce the stress intensity factor at the crack tip in the metal part of the hybrid composite. This mechanism leads to a significant reduction of the crack growth and can be enhanced by introducing favourable residual stresses into the hyb- rid material. For an optimized ARALL material an aluminum sheet thickness of about 0.5 mm and an aramid layer thickness of about 0.25 mm (with a fibre volume content of about 40-50%) are chosen.ARALL decreases the crack growth rates by orders of magnitude, as compared to monolithic aluminum sheets, and is an extremely damage tolerant material.
    Notizen: Hohe Kraftstoffkosten und die Tendenz zu größeren Flugzeugen sind zwei Faktoren, die die Luftfahrtzeug-Konstrukteure zwingen, immer höhere Entwurfspannungen zu wählen. Für die verwendeten Konstruktionswerkstoffe bedeutet dies, daß ihr Ermüdungsverhalten immer wichtiger wird. Dieses Problem kann durch die Entwicklung neuer ermüdungsunempfindlicher hochfester Leichtbauwerkstoffe gelöst werden. In diesem Bericht wird ein neuer Werkstoff vorgestellt, der diesen Forderungen entgegenkommt. Es handelt sich um den aramidfaserverstärkten Aluminiumschicht-Verbundwerkstoff ARALL. Der Hybridverbundwerkstoff besteht aus dünnen, unplattierten Aluminiumblechen einer hochfesten Aluminiumlegierung, die mit einem Metallkleber verbunden sind. In den Kleber sind hochfeste Aramidfasern eingebracht. Treten im Laufe der Lebensdauer eines solchen Werkstoffs Ermüdungsrisse im metallischen Teil des Hybridverbundes auf, so bleiben die hochfesten ermüdungsunempfindlichen Aramidfasern weiterhin intakt und behindern die Rißfortschrittsgeschwindigkeit erheblich herabgesetzt. Diese Rißfortschrittsverzögerung kann noch dadurch erheblich gesteigert werden, daß günstige Eigenspannungen in das Laminat eingebracht werden. Als optimal kann ein Aufbau des ARALL-Werkstoffs angesehen werden, wenn die Aluminiumblechstärke etwa 0,5 mm und die Dicke der aramidfaserverstärkten Schicht etwa 0,25 mm (bei einem Faservolumenanteil von 40-50%) betragen.In bereits durchgeführten Schwingfestigkeitsversuchen wurden bei ARALL Reduktionen in der Rißfortschrittsgeschwindigkeit im Vergleich zu konventionellen Aluminiumlegierungen bis zu einem Faktor von 1000 beobachtet.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 82
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 305-310 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Evaluation of Computer-Controlled Hot Plane Strain Compression Tests for Investigation of Material BehaviourDuring the test the data of specimen temperature, deformation load and ram displacement are collected and stored. The flow curves evaluated predict actual mill loads and can be used to measure softening processes. The differentiation of the cooling curve of the deformed specimen provides information about transformation kinetics. A rather large specimen enables a comprehensive material testing of the simulated processing with the aim of the optimization of thermomechanical treatment.
    Notizen: Während des Versuchsablaufs werden kontinuierlich die Probentemperatur, die Stauchkraft und der Werkzeugweg digital erfaßt und weiter ausgewertet. Die Ermittlung von Fließkurven ermöglicht Aussagen über die Umformkräfte und das Entfestigungsverhalten des Werkstoffs. Die differenzierten Abkühlkurven der gestauchten Probe liefern Informationen über den Umwandlungsablauf im Gefüge. Die Größe der Flachstauchprobe erlaubt eine umfassende Werkstoffprüfung nach der Simulation und damit eine Optimierung thermomechanischer Behandlungsverfahren.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 83
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A100 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 84
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A102 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 85
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Fracture Mechanics Investigations on Cast AluminiumAluminium castings cannot be massproduced economically without casting pores or similar flaws.These flaws must, however, be avoided, at least in the highly stressed regions of cast safety components of automobiles by changes in design or casting procedure. In other regions flaws up to a certain size can be tolerated if it can be shown by calculation and experiment that cracks either will not propagate from these flaws or at least will not reach critical size during the life of the component.Cast aluminium wheels are an example of such a component. Their allowable flaw sizes were determined in the following way: -The stresses occuring in service wer measured in 17 locations in a test rig in the laboratory and on a race track.-The crack propagation characteristics and the ΔKth-values of the cast aluminium material were determined.-Crack propagation was calculated under the stresses measured in service; based on these measured stresses and the fracture mechanics characteristics, locations were selected in the cast aluminium wheel where no flaws can be allowed; in other locations with lower stresses the allowable flaw sizes were calculated with a large safety factor.
    Notizen: Bei gegossenen Aluminium-Bauteilen des Kraftfahrzeugbaues, z. B. bei Rädern, sind Lunker, Poren usw. nicht sicher vermeidbar. Sie können toleriert werden, wenn experimentell und rechnerisch nachgewiesen wird, daß sie mit genügender Sicherheit während der vorgesehenen Betriebszeit nicht zu Schäden führen.Unter der auf der sicheren Seite liegenden Annahme, daß sich ein Lunker gegenüber statischen und schwingenden Beanspruchungen wie ein Ermüdungsriß verhält, kann man mit Hilfe der linear-elastischen Bruchmechanik die Festigkeit des betreffenden Bauteils mit Lunkern gegenüber statischen und schwingenden Beanspruchungen berechnen. Daher wurde in zwei Schritten ein auf der linear-elastischen Bruchmechanik beruhendes Versuchsprogramm durchgeführt, um festzustellen, ob, an welchen Stellen, und bis zu welcher Größe Lunker in gegossenen Pkw-Aluminium-Rädern toleriert werden können. Hierfür wurde u.a. ein neues Verfahren zur Bestimmung der „bruchmechanischen Dauerfestigkeit“ verwendet.Wie gezeigt wird, schreiten Risse von zulässigen Lunkern unter Betriebsbeanspruchungen entweder überhaupt nicht for oder werden nur wenig länger.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 86
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 342-350 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Tribological Behaviour of Filled Polymers and CompositesThe friction and wear behaviour of polymer-steel sliding couples may be changed considerably by using filled polymers. In course of an extensive research work the effect of additions of glass fibers, graphite and polytetrafluoroethylene (PTEF) to polymers for higher temperatures was tested. Additionally the tribological behaviour of PTFE-lead-composite in DU-bearing material was examined. The results show that friction and wear may be reduced by fillers depending on the operating variables. The results can be interpreted by means of the observed tribophysical surface and contact processes.
    Notizen: Das Reibungs- und Verschleißverhalten von Kunststoff-Stahl-Gleitpaarungen kann durch Verwendung von Kunststoffen mit Zusatzstoffen erheblich verändert werden. Im Rahmen einer umfangreichen Forschungsarbeit wurde untersucht, wie sich der Zusatz von Glasfasern, Graphit und Polytetrafluoräthylen (PTFE) in hochwärmebeständigen Kunststoffen auswirkt. Zusätzlich wurde das tribologische Verhalten einer PTFE-Blei-Komponente in einem DU-Lagerwerkstoff untersucht. Die Ergebnisse zeigen, daß sich in Abhängigkeit von den Beanspruchungsbedingungen Reibung und Verschleiß durch Zusatzstoffe verringern lassen. Eine Erklärung ist anhand der beobachteten tribophysikalischen Grenzflächen- und Kontaktvorgänge möglich.
    Zusätzliches Material: 17 Ill.
    Materialart: Digitale Medien
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  • 87
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A105 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 88
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 365-367 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Stabile Geometrie von Oberflächenrissen bei Rißwachstum durch ErmüdungDie sich bei einer Ermüdungsbeanspruchung einstellende Rißgeometrie unter überlagerter Zug- und Biegebeanspruchung wird mit verschiedenen Annahmen berechnet. Die Ergebnisse zeigen im Vergleich zu den in [1] publizierten Resultaten geringe Unterschiede.
    Notizen: Final crack aspect ratios are calculated for alternating combined tension and bending loading using different assumptions. The results are compared with those published in [1] showing small differences.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 89
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 90
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A4 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 91
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 24-31 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Effects of Aging in Inert Gas at 800 to 1000 °C on the Mechanical Properties of X 10 NiCrAlTi32 20 Type AlloysSpecimens of three casts of a X 10 NiCrAlTi32 20 type alloy with different carbon contents (0,04, 0,08 and 0,33 wt%) were annealed at 800, 900 and 1000°C between 6 and 900 h. Tensile- and notched bar impact-tests were performed at room temperature to characterize the changes of mechanical properties due to the heat treatments. The structural changes were recorded by optical metallography, scanning electron microscopy and transmission electron microscopy. The formation of fine dispersed M23C6-precipitates leads to hardening effects, which are lost by coarsening with longer annealing time or higher temperatures, where an embrittlement occurs. Only the low carbon version exhibits a dominant precipitation of Ti(C, N), especially at 1000°C, which maintains its ductility.
    Notizen: Versuchsdurchführung unter Argonatmosphäre bei 800, 900 und 1000 °C - mechanische Kennwerte bei Raumtemperatur in Abhängigkeit von Prüftemperatur und Auslagerzeit - licht- und elektronenoptische Untersuchung des Mikrogefüges - Zuordnung mechanischer Kennwerte und Mikrogefüge.
    Zusätzliches Material: 22 Ill.
    Materialart: Digitale Medien
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  • 92
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 35-35 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 93
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A18 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 94
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A12 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 95
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A20 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 96
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 70-71 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 97
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A24 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 98
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 91-97 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Constitutive Equations for Inelastic Analysis with Reference to the Austenitic Stainless Steel X 6 CrNi 18 11 (Type 304 ss)The design analysis of high temperature components requires stress-strain relations for structural materials under consideration. These are to be based on quantitative descriptions of the mechanical behaviour under the conditions of operation.Average stress-strain relations for the time-independent and time-dependent material behavior are derived for a representative product form of the stainless steel X 6 CrNi 18 11 by means of the actual data from a set of tensile and creep experiments.The actual data at temperatures of 20°C and 550°C are compared with the derived average constitutive relations. The results are discussed and compared with literature data for the corresponding American steel AISI 304 ss and the Japanese steel SUS 304, resp.
    Notizen: Zum Festigkeitsnachweis von im Hochtemperaturbereich betriebenen Komponenten werden für hochbeanspruchte Konstruktionsbereiche inelastische Spannungs-Dehnungsanalysen auf der Grundlage quantitativer Beschreibungen des Werkstoffverhaltens benötigt.Anhand einer realen Meßdatengesamtheit aus Zug- und Kriechversuchen werden für eine repräsentative Halbzeugform des Stahles X 6 CrNi 18 11 die mittleren Spannungs-Dehnungs-Beziehungen für das zeitunabhängige und zeitabhängige Materialverhalten abgeleitet. Bei Temperaturen von 20°C und 550°C werden die Meßdaten einer typischen Materiallieferung den abgeleiteten mittleren werkstoffmechanischen Beziehungen vergleichend gegenübergestellt. Das Ergebnis wird diskutiert und mit Literaturwerten für den artgleichen amerikanischen Stahl AISI 304 ss sowie den entsprechenden japanischen Stahl SUS 304 verglichen.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 99
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 98-105 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Characterisation of Adherence of Precious Alloy to Dental CeramicLaminated metal-ceramic composites were produced from two Aubase alloys and two ceramic powders. For part of the specimen an extra Aurich layer was brought into the metal-ceramic interface. Microscopic investigations showed enrichment of non precious alloying elements in the metallic region adjacent to the interface and a sheet of enhanced porosity (about 5-15%) in the ceramic region adjacent to the interface. After producing a Chevron notch in the interface the composite specimens were fractured in a controlled mode in four point bending. As the crack was at least partly running along the ceramic zone of enhanced porosity near the interface, the average crack resistance R̄ of the interface could be determined. In specimens without an extra Au-rich layer R̄ was between 3 and 12 J/m2 and thus less than the R̄-value of the ceramic (R̄ 12 J/m2). The relatively large scatter is supposed to be mainly due to internal stresses. Specimens containing an extra Au-rich layer showed high R̄-values (up to 36 J/m2) due to good interlocking of metal and ceramic.
    Notizen: Aus zwei Edelmetall-Aufbrennlegierungen und zwei keramischen Massen der Dentaltechnik wurden Metall-Keramik-Schichtverbundproben hergestellt, wobei bei einem Teil der Proben zusätzlich eine goldreiche Schicht zwischen die Verbundpartner eingebracht wurde. Die mikroskopische Untersuchung zeigte, daß sich metallseitig an der Grenzfläche unedle Legierungsbestandteile angereichert hatten und keramikseitig eine flächenhafte Zone erhöhter Porosität (etwa 5-15%) gebildet wurde. Die in der Grenzfläche mit einem Spitzkerb versehenen Proben wurden im Vierpunktbiegeversuch bei Raumtemperatur kontrolliert gebrochen. Der Riß verlief zumindest teilweise in der grenzflächennahen, porösen Zone der Keramik, so daß der mittlere Rißwiderstand R̄ der Grenzfläche bestimmt werden konnte. Für Proben ohne goldreiche Zwischenschicht lag R̄ zwischen 3 und 12 J/m2 und damit in der Regel niedriger als in der Keramik (etwa 12 J/m2). Die relativ große Streuung wird vorwiegend auf herstellungsbedingte innere Spannungen zurückgeführt. Für die hohen R̄-Werte der Proben mit goldreicher Zwischenschicht (bis 36 J/m2) wird die gute Verzahnung zwischen Metall und Keramik als ursächlich angesehen.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 100
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. A34 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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