7,522 research outputs found

    Pseudo-Anosov flows in toroidal manifolds

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    We first prove rigidity results for pseudo-Anosov flows in prototypes of toroidal 3-manifolds: we show that a pseudo-Anosov flow in a Seifert fibered manifold is up to finite covers topologically equivalent to a geodesic flow and we show that a pseudo-Anosov flow in a solv manifold is topologically equivalent to a suspension Anosov flow. Then we study the interaction of a general pseudo-Anosov flow with possible Seifert fibered pieces in the torus decomposition: if the fiber is associated with a periodic orbit of the flow, we show that there is a standard and very simple form for the flow in the piece using Birkhoff annuli. This form is strongly connected with the topology of the Seifert piece. We also construct a large new class of examples in many graph manifolds, which is extremely general and flexible. We construct other new classes of examples, some of which are generalized pseudo-Anosov flows which have one prong singularities and which show that the above results in Seifert fibered and solvable manifolds do not apply to one prong pseudo-Anosov flows. Finally we also analyse immersed and embedded incompressible tori in optimal position with respect to a pseudo-Anosov flow.Comment: 44 pages, 4 figures. Version 2. New section 9: questions and comments. Overall revision, some simplified proofs, more explanation

    Thoracic duct drainage in organ transplantation: Will it permit better immunosuppression?

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    It is possible that thoracic-duct drainage, a major but neglected immunosuppressive adjunct, can have an important impact on organ transplantation. If thoracic-duct drainage is started at the time of transplantation, the practicality of its use in cadaveric cases is greatly enhanced. With kidney transplantation, the penalty of not having pretreatment for the first organ is compensanted by the automatic presence of pretreatment if rejection is not controlled and retransplantation becomes necessary. The advantage of adding thoracic-duct drainage to conventional immunosuppression may greatly enhance the expectations for the transplantation of extrarenal organs, such as the liver, pancreas, heart, and lung. There is evidence that pretreatment with thoracic-duct drainage of patients with cytotoxic antibodies may permit successful renal transplantation under these otherwise essentially hopeless conditions. Exploration of the neglected but potentially valuable tool of thoracic-duct drainage seems to the authors to be highly justified in other centers

    Airline Liability for Loss, Damage or Delay of Passenger Baggage

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    The article discusses remedies and methods of enforcing airline liability for loss, damage or delay of passenger baggage. The article includes a discussion of the law as it relates both to domestic flights and to international flights where passenger luggage is lost, damaged or delayed. The article includes a discussion of the Warsaw Convention as it relates to international flights and of the Federal Aviation Regulations applicable in the case of domestic flights

    Direct introduction of cloned DNA into the sea urchin zygote nucleus, and fate of injected DNA

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    A method is described for microinjection of cloned DNA into the zygote nucleus of Lytechinus variegatus. Eggs of this species are unusually transparent, facilitating visual monitoring of the injection process. The initial fate of injected DNA fragments appears similar to that observed earlier for exogenous DNA injected into unfertilized egg cytoplasm. Thus after end-to-end ligation, it is replicated after a lag of several hours to an extent indicating that it probably participates in most of the later rounds of DNA synthesis undergone by the host cell genomes during cleavage. The different consequences of nuclear versus cytoplasmic injection are evident at advanced larval stages. Larvae descendant from eggs in which exogenous DNA was injected into the nuclei are four times more likely (32% versus 8%) to retain this DNA in cell lineages that replicate very extensively during larval growth, i.e. the lineages contributing to the imaginal rudiment, and thus to display greatly enhanced contents of the exogenous DNA. Similarly, 36% of postmetamorphic juveniles from a nuclear injection sample retained the exogenous DNA sequences, compared to 12% of juveniles from a cytoplasmic injection sample. However, the number of copies of the exogenous DNA sequences retained per average genome in postmetamorphic juveniles was usually less than 0.1 (range 0.05-50), and genome blot hybridizations indicate that these sequences are organized as integrated, randomly oriented, end-to-end molecular concatenates. It follows that only a small fraction of the cells of the average juvenile usually retains the exogenous sequences. Thus, even when introduced by nuclear microinjection, the stable incorporation of exogenous DNA in the embryo occurs in a mosaic fashion, although in many recipients the DNA enters a wider range of cell lineages than is typical after cytoplasmic injection. Nuclear injection would probably be the route of choice for studies of exogenous DNA function in the postembryonic larval rudiment
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