Oxidation tests of Ni alloys with additions of Zr and Y were carried out at 1000 deg C under low oxygen partial pressure. Oxidation kinetics as well as particle morphologies and structures were ...investigated by scanning-electron microscopy, energy-dispersive X-ray analvsis and X-ray diffraction. Internal oxidation was observed under all circumstances. The kinetics of the internal oxidation was determined. A binary Ni-Zr alloy shows in situ internal oxidation according to theory. Yttrium was found to have a strong influence on the oxidation kinetics. Even minor Y contents considerably accelerate internal oxidation. Fast internal oxidation of ternary Ni-Zr-V alloys cannot be explained by standard internal oxidation theory.
Recently the concept of dissociative identity disorder (formerly known as multiple personality disorder) has attracted increasing public and scientific interest. However, it is rarely diagnosed in ...the clinical setting. the reported case of a 47-year-old woman with a history of child abuse demonstrates the problems of differential diagnosis. A number of psychopathologic symptoms pointed to a multiple personality disorder, but in the follow-up psychotic symptoms such as delusions, possible hallucinations and bizarre behavior clearly emerged. The differential diagnosis of dissociative identity disorder includes paranoid schizophrenia, as in the case described, borderline personality disorder, hysteria, simulation and the false memory syndrome. Finally, social and cultural factors have to be considered.
(1) The complex of endophytic insects in flower heads of Cirsium heterophyllum (L.) Hill (Cardueae) was dominated by the tephritid fly Tephritis conura Loew (Diptera: Tephritidae). An average of ...40-50% of the flower heads in a plant stand with a mean of 8.9 individuals per head were attacked by T. conura. (2) Larval densities of T. conura differed from one plant stand to another. However, within a plant stand annual density fluctuations were small during the 4 years of the study. In spite of high densities in some plant stands, the carrying capacity of the heads was rarely reached. (3) There was no apparent regulation of fly numbers by density-dependent processes during larval development over a wide range of natural densities. Mortalities from parasitoids and predation by microlepidoptera were density-independent. (4) After experimental `extermination' of T. conura subpopulations, plant stands were recolonized within one generation. Densities before and after the manipulation were comparable. (5) In natural plant stands levels of infestation were determined every year by colonization processes. Attack rates were mainly influenced by the synchronization of the oviposition period with bud development in a plant stand. (6) Density-dependent `regulation' occurred only at high experimental densities and was manifested in adult behaviour during the oviposition period (interactions between searching adults, ability to discriminate against already infested buds, adult dispersal).
The distribution of the eggs by females of Tephritis conura Loew (Diptera: Tephritidae), whose larvae live endophytically in flower heads of Cirsium heterophyllum (L.) Hill (Cardueae), was analyzed. ...Females oviposited exclusively in young buds, where the length of developing florets was between 0.2 and 0.8 mm. Eggs of T. conura are laid in batches. Batch sizes show a highly variable but characteristic pattern. In natural populations multiple ovipositions (two or more batches per bud) commonly occur. On the basis of field data models for the spatial and seasonal distribution of the eggs on distinct resource units (flower heads) are developed. It is concluded that in natural populations of T. conura the distribution of egg batches is mainly a random process. Nevertheless, overcrowding of flower heads and food shortage for the larvae are observed only occasionally since 1) the mean egg number per individual batch does not exceed the capacity of even a small flower head, and 2) the short time period during which each bud is suitable for oviposition reduces the probability of multiple ovipositions.
The present study was undertaken because of the paucity of information on peroxisomes in molluscs and the increasing importance of these organisms as sensitive indicators of environmental pollution. ...Peroxisomes were identified by electron microscopy in all three main cell types of the digestive gland of the bivalve mollusc Mytilus galloprovincialis Lmk. They stained weakly with the alkaline diaminobenzidine reaction but showed distinct immunolabeling with an antibody against mammalian catalase by the postembedding protein A-gold procedure. In addition, mussel digestive gland peroxisomes were isolated by differential and metrizamide-density gradient centrifugation, and a 30-fold enrichment of catalase and a 20-fold enrichment of palmitoyl-CoA oxidase was obtained over the initial homogenate. By Western blotting, isolated peroxisomes crossreacted with antibodies to catalase and, furthermore, specific and prominent labeling of isolated peroxisomes was also demonstrated in thin sections incubated with anti-catalase antibodies. These observations establish that peroxisomes in molluscan digestive gland contain the peroxisomal marker enzymes catalase and acyl-CoA oxidase and that they can be labeled by cytochemical and immunocytochemical techniques. Further studies of alterations of molluscan peroxisomes by environmentally relevant xenobiotics are warranted.
We have studied spin dephasing and spin diffusion in a high-mobility two-dimensional electron system, embedded in a GaAs/AlGaAs quantum well grown in the 110 direction, by a two-beam Hanle ...experiment. For very low excitation density, we observe spin lifetimes of more than 16 ns, which rapidly decrease as the pump intensity is increased. Two mechanisms contribute to this decrease: the optical excitation produces holes, which lead to a decay of electron spin via the Bir-Aranov-Pikus mechanism and recombination with spin-polarized electrons. By scanning the distance between the pump and probe beams, we observe the diffusion of spin-polarized electrons over more than 20 microns. For high pump intensity, the spin polarization in a distance of several microns from the pump beam is larger than at the pump spot, due to the reduced influence of photogenerated holes.
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