Bibliothek

Notizen: We report a new case of pleomorphic fibroma of the skin arising on the face. The lesion was polypoid and fibrous, located on the dermis, and formed by coarse collagen bundles with sparse cells. It was also characterized by the presence of cellular atypia and pleomorphism without mitosis. Immunohistochemistry showed staining for vimentin and actin and negativity for S-100, CD34, CD68, α-1-antichymotrypsin and α-1-antitrypsin antigens, supporting a myofibroblastic origin. A few isolated cells also showed granular cytoplasmic detection of factor XIIIa. Although the disorder has been previously considered to be a tumour of preferential localization on the trunk or extremities, this does not always hold true as four of the 14 reported cases arose on the head. Pleomorphic fibroma is a benign condition and is we believe a variant of sclerotic fibroma.

Notizen: Generalized (diffuse) plane xanthoma (GPX) is a nor-molipacmic xanthomatosis that is very frequently associated with a haematological disorder, and especially with monoclonal gammapathies, which it may precede by several months or years. Here, we report a case of GPX associated with idiopathic Bence–Jones proteinuria, a very rare type of monoclonal gammopathy of undetermined significance. To our knowledge, this association has not been previously described.

Notizen: Abstract— This paper analyses the validity of the fracture mechanics approach to hydrogen assisted cracking in metals on the basis of K-dominance over both the stress-strain state and the accumulation of hydrogen in the fracture process zone. Stress-strain assisted diffusion of hydrogen is considered as the rate controlling factor of hydrogen assisted cracking under sustained or quasi-static loading conditions. The discrepancy in the crack tip zone between the far-field affected diffusion and the asymptotically driven (K-controlled) process is elucidated. The far field (i.e., the stress-strain field which is not K-dominated) is shown to have a minor effect on near-tip hydrogen diffusion. It can only widen the scatter band of crack growth rates in the near-threshold portion of the crack growth kinetics curve.

Notizen: The adherence of yeasts to oral mucous cells is one of the main characteristics of the pathogenicity of this fungus. We studies adherence by means of a radiometric test to improve the method. We compared a sample of 40 strains of Candida albicans isolated from the buccal mucosa of HIV-infected patients with 40 strains isolated from non-HIV patients. We found that buccally isolated C.albicans strains from patients in the initial stages of AIDS adhered to oral mucous cells less than the buccally isolated C.albicans strains from subjects without HIV infection. Adherence among the strains of HIV patients increased with the disease stage until it exceeded that of the normal subjects in proportion to the decrease in the CD4/CD8 ratio. The selection of resistant strains by the preliminary antifungal treatments gave us a partial explanation for this increase. Further research should be carried out to compare these results with those obtained from atypical strains and species with high pathogenic potential, such as Candida dubliniensis, which is frequently isolated from advanced AIDS, in order to prevent systemic infections in these patients.

Notizen: Abstract This is a summary of the achievements of a major research line at the Materials Science Department of the University of La Coruña (Spain) in the field of environmentally assisted cracking in general and hydrogen degradation in particular. It deals with a materials science approach to the study of corrosion-assisted cracking of progressively drawn pearlitic steels for use in civil engineering. The approach is based on the fundamental idea of materials science of linking the microstructure of different steels (progressively oriented as a consequence of the process of manufacturing by cold drawing) with their macroscopic stress-corrosion behavior (increasingly anisotropic as the degree of cold drawing increases). In the first part of the research, we performed metallographic analysis and gave special attention to the evolution with cold drawing of the two basic microstructural levels: pearlite colonies (first level) and pearlitic lamellae (second level). For the first microstructural level, we observed progressive eleongation and orientation of the pearlite colonies in the direction of cold drawing (axis of the wire). For the second microstructural level, the analysis revealed an increase in the closeness of packing (with a decrease in the interlamellar spacing) and progressive orientation of the pearlitic lamellar microstructure in the direction of cold drawing. Therefore, in the process of cold drawing, both the pearlite colonies and pearlitic lamellar microstructure tend to align in a direction quasiparallel to the axis of the wire. In the second part of the research, we carried out a program of stress-corrosion-cracking tests under both cathodic and anodic conditions to promote two very different mechanisms of cracking: hydrogen-assisted cracking (HAC) and localized anodic dissolution (LAD). Both types of stress corrosion tests confirm that steels subjected to cold drawing exhibit anisotropic behavior connected with clear changes in the direction of crack propagation, which approaches the axis of the wire or the direction of cold drawing. For both mechanisms (HAC and LAD), there is a strong correlation between the angles of microstructural orientation (on the levels of pearlitic colonies and lamellae) and the angles of propagation of macroscopic cracks, which clearly demonstrates the influence of the oriented microstructure (and, thus, of the process of manufacturing by increasing cold drawing) on the macroscopic corrosion-assisted behavior of steel wires.

Notizen: Abstract We summarize the achievements of a major research line at the Department of Materials Science of the University of La Coruña (Spain) in the field of environmentally-assisted cracking in general and hydrogen degradation in particular. We analyze the meaning and significance of the fracture-mechanics approach to hydrogen-assisted cracking and study the problem ofK-dominance not only over the mechanical aspects of the phenomenon but also over the environmental (physicochemical) factors affecting the entire coupled process of hydrogenation and failure. Two key factors capable of violating the unambiguous behavior of the kinetic diagram of crack growthv=v (K) are discussed: the role of the far stress-strain field (i.e., the stress-strain field which is notK-dominated) and the effect of the history of hydrogenation and crack growth. For this purpose, we consider the stress-strain-assisted diffusion of hydrogen regarded as a rate-controlling factor of hydrogen-assisted cracking under sustained or quasistatic loads. It is shown that the far field produces a minor effect on the near-tip diffusion of hydrogen. This can only increase the spread in crack growth rates in the near-threshold part of thev (K)-curve. As far as the influence of the history is concerned, we discovered that the processes of hydrogenation and crack growth are coupled, eachof them affects the other, and, hence, the kinetic diagram of crack growthv=v (K) is not one-to-one as should be for an intrinsic property of the material. However, there exists a special mode of steady-state crack growth when hydrogen-assisted cracking becomes aK-dominated process and the corresponding plot of the steady-state ratev as a function ofK becomes unambiguous (as a characteristic curve of the material) and, thus, can be used in the engineering practice for a more conservative evaluation of the crack-growth resistance of materials and structural integrity.