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Legionella pneumophila is the causative agent of Legionnaires´ disease. The bacterium’s pathogenicity is based on its ability to survive and multiply efficiently inside human alveolar cells. Therefore, L. pneumophila is not only an important pathogen, but can also be used as a probe to investigate host cell function as for example, in the cellular trafficking pathway. In this study, we establish a new model of how this pathogen efficiently constructs its replicative niche, the Legionella containing vacuole (LCV), inside the host cytosol, enabling its dissemination. To investigate the mechanisms that lead to effective exploitation of the host cell, we down-regulated specific host cellular proteins via siRNA technology and measured the subsequent impact on L. pneumophila replication. The results suggest that the LCV mimicks the Golgi app...
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As partial justification of their framework for iterated belief revision Darwiche and Pearl convincingly argued against Boutiliers natural revision and provided a prototypical revision operator that fits into their scheme. We show that the Darwiche-Pearl arguments lead naturally to the acceptance of a smaller class of operators which we refer to as admissible. Admissible revision ensures that the penultimate input is not ignored completely, thereby eliminating natural revision, but includes the Darwiche-Pearl operator, Nayaks lexicographic revision operator, and a newly introduced operator called restrained revision. We demonstrate that restrained revision is the most conservative of admissible revision operators, effecting as few changes as possible, while lexicographic revision is the least conservative, and point out that restrain...
A high temperature silicon production process using existing electric arc heater technology is discussed. Silicon tetrachloride and a reductant, liquid sodium, were injected into an arc heated mixture of hydrogen and argon. Under these high temperature conditions, a very rapid reaction occurred, yielding silicon and gaseous sodium chloride. Techniques for high temperature separation and collection of the molten silicon were developed. The desired degree of separation was not achieved. The electrical, control and instrumentation, cooling water, gas, SiCl4, and sodium systems are discussed. The plasma reactor, silicon collection, effluent disposal, the gas burnoff stack, and decontamination and safety are also discussed. Procedure manuals, shakedown testing, data acquisition and analysis, product characterization, disassembly and deconta...
Given the intense effect visual impairment has on the quality of life of older persons, there is an increased awareness in social work of the growing need and demand for support services for older persons who are visually impaired. The study explores the socio-emotional experiences of these persons from a life stage and ecological perspective. The investigation shows that visual impairment severely influences the daily functioning of older persons. The findings indicate the need for preventative services, assessment of the influence of visual impairment on the socio-emotional functioning of older persons, and social work interventions at individual, family and community levels.
Micromixing in a tubular polymn. reactor is characterized by the mol. wt. of polystyrene obtained in the presence of a chain transfer agent. Monomer and the transfer agent are fed sep. into the reactor. For const. overall inlet concns., the mean mol. wt. produced is strongly dependent on mixing intensity. Expts. were carried out in a pilot plant loop tubular reactor of different configurations and monomer conversions ?80%. The degree of segregation as a function of energy dissipation and the characteristic reaction time can be described by an empirical correlation. It could be shown that the design of the mixer can change considerably the micromixing efficiency. [on SciFinder (R)]
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