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  • 1
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    Lack of protective immunity against reinfection with hepatitis C virus (1992)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1992-10-02
    Description: Some individuals infected with hepatitis C virus (HCV) experience multiple episodes of acute hepatitis. It is unclear whether these episodes are due to reinfection with HCV or to reactivation of the original virus infection. Markers of viral replication and host immunity were studied in five chimpanzees sequentially inoculated over a period of 3 years with different HCV strains of proven infectivity. Each rechallenge of a convalescent chimpanzee with the same or a different HCV strain resulted in the reappearance of viremia, which was due to infection with the subsequent challenge virus. The evidence indicates that HCV infection does not elicit protective immunity against reinfection with homologous or heterologous strains, which raises concerns for the development of effective vaccines against HCV.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Farci, P -- Alter, H J -- Govindarajan, S -- Wong, D C -- Engle, R -- Lesniewski, R R -- Mushahwar, I K -- Desai, S M -- Miller, R H -- Ogata, N -- New York, N.Y. -- Science. 1992 Oct 2;258(5079):135-40.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Hepatitis Viruses Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1279801" target="_blank"〉PubMed〈/a〉
    Keywords: Acute Disease ; Aged ; Alanine Transaminase/biosynthesis ; Animals ; Base Sequence ; Hepacivirus/physiology ; Hepatitis Antibodies/biosynthesis ; Hepatitis C/*immunology ; Hepatitis C Antibodies ; Humans ; Immunity, Active ; Longitudinal Studies ; Molecular Sequence Data ; Pan troglodytes ; Polymerase Chain Reaction ; Sequence Homology ; Transcription, Genetic ; Viremia ; Virus Replication
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
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    The long noncoding RNA SPRIGHTLY acts as an intranuclear organizing hub for pre-mRNA molecules (2017)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2017-05-04
    Description: Molecular mechanisms by which long noncoding RNA (lncRNA) molecules may influence cancerous condition are poorly understood. The aberrant expression of SPRIGHTLY lncRNA, encoded within the drosophila gene homolog Sprouty-4 intron, is correlated with a variety of cancers, including human melanomas. We demonstrate by SHAPE-seq and dChIRP that SPRIGHTLY RNA secondary structure has a core pseudoknotted domain. This lncRNA interacts with the intronic regions of six pre-mRNAs: SOX5 , SMYD3 , SND1 , MEOX2 , DCTN6 , and RASAL2 , all of which have cancer-related functions. Hemizygous knockout of SPRIGHTLY by CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 in melanoma cells significantly decreases SPRIGHTLY lncRNA levels, simultaneously decreases the levels of its interacting pre-mRNA molecules, and decreases anchorage-independent growth rate of cells and the rate of in vivo tumor growth in mouse xenografts. These results provide the first demonstration of an lncRNA’s three-dimensional coordinating role in facilitating cancer-related gene expression in human melanomas.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Chaotic orbits of tumbling ellipsoids (2020)
    Cambridge University Press
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    Publication Date: 2020-09-21
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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  • 4
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    Mammatus cloud formation by settling and evaporation (2020)
    Cambridge University Press
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    Publication Date: 2020-07-24
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 5
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    Stability of spatially developing boundary layers in pressure gradients (1995)
    Cambridge University Press
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    Publication Date: 1995-10-10
    Description: A new formulation of the stability of boundary-layer flows in pressure gradients is presented, taking into account the spatial development of the flow and utilizing a special coordinate transformation. The formulation assumes that disturbance wavelength and eigenfunction vary downstream no more rapidly than the boundary-layer thickness, and includes all terms nominally of order R-1in the boundary-layer Reynolds number R. In Blasius flow, the present approach is consistent with that of Bertolotti et al. (1992) to O(R-1) but simpler (i.e. has fewer terms), and may best be seen as providing a parametric differential equation which can be solved without having to march in space. The computed neutral boundaries depend strongly on distance from the surface, but the one corresponding to the inner maximum of the streamwise velocity perturbation happens to be close to the parallel flow (Orr-Sommerfeld) boundary. For this quantity, solutions for the Falkner-Skan flows show the effects of spatial growth to be striking only in the presence of strong adverse pressure gradients. As a rational analysis to O(R-1) demands inclusion of higher-order corrections on the mean flow, an illustrative calculation of one such correction, due to the displacement effect of the boundary layer, is made, and shown to have a significant destabilizing influence on the stability boundary in strong adverse pressure gradients. The effect of non-parallelism on the growth of relatively high frequencies can be significant at low Reynolds numbers, but is marginal in other cases. As an extension of the present approach, a method of dealing with non-similar flows is also presented and illustrated. However, inherent in the transformation underlying the present approach is a lower-order non-parallel theory, which is obtained by dropping all terms of nominal order R-1except those required for obtaining the lowest-order solution in the critical and wall layers. It is shown that a reduced Orr-Sommerfeld equation (in transformed coordinates) already contains the major effects of non-parallelism. © 1995, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 6
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    Transition delay by surface heating: a zonal analysis for axisymmetric bodies (2000)
    Cambridge University Press
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    Publication Date: 2000-09-10
    Description: It has long been known from linear stability theory that heating a surface immersed in water flow tends to stabilize the boundary layer on the surface, suggesting that there may be a corresponding delay in transition. Experiments confirm the suggestion, but based on intermittency data on a heated body of revolution (Lauchle and Gurney 1984) it has been inferred that incremental changes in transition Reynolds number diminish as the overheat increases. The parameter chosen to locate transition in the analysis leading to this conclusion corresponds to the point where the intermittency is 0.5. However, intermittency distributions in the transition zone on an axisymmetric body may contain what have been called 'subtransitions' (Narasimha 1984). Taking this possibility into account, we formulate here a model for the variation of intermittency with flow Reynolds number at a fixed station on the body, as in the experiments. The rate at which turbulent spots merge with each other is shown to determine the location of subtransition. The transition onset Reynolds number (corresponding to the location where intermittency begins to depart from zero), inferred from the data on the basis of this model, shows a continuing increase with the temperature overheat, a trend in closer agreement with stability theory; but the axisymmetric body geometry results in a very short transition zone, countering in part the benefits of transition delay.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 7
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    Estimating amplitude ratios in boundary layer stability theory: a comparison between two approaches (2001)
    Cambridge University Press
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    Publication Date: 2001-07-23
    Description: We first demonstrate that, if the contributions of higher-order mean flow are ignored, the parabolized stability equations (Bertolotti et al. 1992) and the 'full' non-parallel equation of Govindarajan & Narasimha (1995, hereafter GN95) are both equivalent to order R-1 in the local Reynolds number R to Gaster's (1974) equation for the stability of spatially developing boundary layers. It is therefore of some concern that a detailed comparison between Gaster (1974) and GN95 reveals a small difference in the computed amplitude ratios. Although this difference is not significant in practical terms in Blasius flow, it is traced here to the approximation, in Gaster's method, of neglecting the change in eigenfunction shape due to flow non-parallelism. This approximation is not justified in the critical and the wall layers, where the neglected term is respectively O(R-2/3) and O(R-1) compared to the largest term. The excellent agreement of GN95 with exact numerical simulations, on the other hand, suggests that the effect of change in eigenfunction is accurately taken into account in that paper.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 8
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    Stability of flow through a slowly diverging pipe (2005)
    Cambridge University Press
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    Publication Date: 2005-05-25
    Description: Although the critical Reynolds number for linear instability of the laminar flow in a straight pipe is infinite, we show that it is finite for a divergent pipe, and approaches infinity as the inverse of the divergence angle. The velocity profile at the threshold of inviscid stability is obtained. A non-parallel analysis yields linear instability at surprisingly low Reynolds numbers, of about 150 for a divergence of 3°, which would suggest a role for such instabilities in the transition to turbulence. A multigrid Poisson equation solver is employed for the basic flow, and an extended eigenvalue method for the partial differential equations describing the stability. © 2005 Cambridge University Press.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 9
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    The critical Reynolds number of a laminar incompressible mixing layer from minimal composite theory (2006)
    Cambridge University Press
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    Publication Date: 2006-09-28
    Description: According to parallel-flow theory based on the Orr-Sommerfeld equation, a mixing layer is unstable at all Reynolds numbers. However this is untenable from energy considerations, which demand that there exist a non-zero Reynolds number below which disturbances cannot extract net energy from the mean flow. It is shown here that a linear stability analysis of similarity solutions of the plane mixing layer, including the effects of flow non-parallelism using the minimal composite theory and the properties of adjoints, following Govindarajan & Narasimha (Theor. Comput. Fluid Dyn. vol. 19, 2005, p. 229) resolves the issue by yielding a non-zero critical Reynolds number for co-flowing streams of any velocity ratio. The critical Reynolds number for the total disturbance kinetic energy is found to be close to 30 for all velocity ratios in the range from zero to unity. © 2006 Cambridge University Press.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 10
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    The effect of wall heating on instability of channel flow (2007)
    Cambridge University Press
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    Publication Date: 2007-04-19
    Description: A comprehensive study of the effect of wall heating or cooling on the linear, transient and secondary growth of instability in channel flow is conducted. The effect of viscosity stratification, heat diffusivity and of buoyancy are estimated separately, with some unexpected results. From linear stability results, it has been accepted that heat diffusivity does not affect stability. However, we show that realistic Prandtl numbers cause a transient growth of disturbances that is an order of magnitude higher than at zero Prandtl number. Buoyancy, even at fairly low levels, gives rise to high levels of subcritical energy growth. Unusually for transient growth, both of these are spanwise-independent and not in the form of streamwise vortices. At moderate Grashof numbers, exponential growth dominates, with distinct Poiseuille-Rayleigh-Bénard and Tollmien-Schlichting modes for Grashof numbers up to ∼ 25 000, which merge thereafter. Wall heating has a converse effect on the secondary instability compared to the primary instability, destabilizing significantly when viscosity decreases towards the wall. It is hoped that the work will motivate experimental and numerical efforts to understand the role of wall heating in the control of channel and pipe flows. © 2007 Cambridge University Press.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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