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- Marcaide, J. M., et al.
(författare)
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Discovery of shell-like radio-structure in SN1993J
- 1995
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Ingår i: Nature. - London : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 373:6509, s. 44-45
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Tidskriftsartikel (refereegranskat)abstract
- SUPERNOVA explosions are poorly understood, partly because of difficulties in modelling them theoretically(1), and partly because there have been no supernovae observed in our Galaxy since the invention of the telescope. But the recent discovery(2) of supernova SN1993J in the nearby galaxy M81 offers an opportunity to investigate the evolution of the remnant, and its interaction with the surrounding interstellar medium, at high resolution. Here we present radio observations of SN1993J, made using very-long-baseline interferometry, which show the development of a shell structure. This 8-month-old radio shell is the youngest ever discovered in a supernova. The data suggest that the supernova explosion and the expanding shell of the remnant have nearly spherical symmetry, with small deviations where some parts of the shell are brighter than others. If these deviations arise because of variations in the density of the shell, this may reconcile earlier reports of symmetric radio emission(3) with the observed optical asymmetry(4,5), as the density variations could easily cause the latter. We infer that the radio emission is generated at the interface(6-9), where the surrounding gas is shocked by the ejecta.
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- Warrier, Indira, et al.
(författare)
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Factor IX inhibitors and anaphylaxis in hemophilia B
- 1997
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Ingår i: Journal of Pediatric Hematology/Oncology. - : Ovid Technologies (Wolters Kluwer Health). - 1077-4114 .- 0192-8562. ; 19:1, s. 23-27
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: We present clinical and laboratory data on 18 children from 12 hemophilia treatment centers in the United States, Canada, and Europe with the purpose of disseminating information regarding a recently recognized, potentially life-threatening complication of treatment in very young children with hemophilia B. Patients and Methods: Twelve hemophilia centers from the United States, Canada, and Europe provided clinical information and laboratory data concerning 18 children who had severe allergic reactions to infused factor (F) IX in close association with the development of an inhibitor to FIX. Laboratory testing for establishment of the diagnosis of hemophilia B and inhibitor to FIX was done locally at the centers treating these patients. FIX gene analysis was performed at one of six molecular genetics institutes. Results: All 18 children had severe hemophilia B, and in each an inhibitor antibody to FIX developed. The median age at the time of anaphylaxis (or anaphylactoid reaction) was 16 months, and the median number of exposure days to FIX was 11. The FIX inhibitor was detected almost simultaneously with the first occurrence of anaphylaxis in 12 of 18 patients. Maximum inhibitor liters were 4.5-600 Bethesda units (BU), with a median titer of 48 BU. FIX gene analysis, performed in 17 of 18 patients, demonstrated complete deletion of the FIX gene in 10 and major derangements in seven. Immune tolerance induction (ITI) regimens have been attempted in 12 patients, with generally poor responses. Two of the 12 experienced nephrotic syndrome while on ITI. Recombinant FVIIa has been successfully used to treat bleeding episodes in 11 of these children. Conclusion: Physicians treating young children with hemophilia B should be aware of the potentially life- threatening complication of anaphylaxis. Children with complete gene deletions or major derangements of the FIX gene appear to be at greater risk. Those identified by genotype as being at greater risk may need to receive their first 10-20 treatments in a medical facility equipped for handling such emergencies. Recombinant FVIIa, although not licensed for use in the United States, appears to be the most suitable treatment option for bleeding episodes in such patients.
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- Bone, L., et al.
(författare)
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New connexin32 muations associated with X-linked Charcot-Marie-Tooth disease
- 1995
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Ingår i: Neurology. - 0028-3878 .- 1526-632X. ; 45:10, s. 1863-6
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Tidskriftsartikel (refereegranskat)abstract
- Analysis of the connexin32 gene in patients with X-linked Charcot-Marie-Tooth disease shows mutations distributed throughout the molecule, with all domains affected except the fourth transmembrane domain and the distal carboxy terminus. Sequence analysis of DNA from 19 unrelated patients detected six novel mutations and three previously reported mutations. Identification of additional mutations extends the distribution of connexin32 mutations in X-linked Charcot-Marie-Tooth disease and shows that specific mutations recur in additional families.
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- Montgomery, R., et al.
(författare)
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A nonintegrable sub-Riemannian geodesic flow on a Carnot group
- 1997
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Ingår i: Journal of Dynamical and Control Systems. - 1079-2724. ; 3:4, s. 519-530
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Tidskriftsartikel (refereegranskat)abstract
- Graded nilpotent Lie groups, or Carnot groups, are to sub-Riemannian geometry as Euclidean spaces are to Riemannian geometry. They are the metric tangent cones for this geometry. Hoping that the analogy between sub-Riemannian and Riemannian geometry is a strong one, one might conjecture that the sub-Riemannian geodesic flow on any Carnot group is completely integrable. We prove this conjecture to be false by showing that the sub-Riemannian geodesic flow is not algebraically completely integrable in the case of the group whose Lie algebra consists of 4 by 4 upper triangular matrices. As a corollary, we prove that the centralizer for the corresponding quadratic "quantum" Hamiltonian in the universal enveloping algebra of this Lie algebra is "as small as possible."
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