Search Results - (Author, Cooperation:M. Ramamurthy)

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  1. 1
    Staff View
    Publication Date:
    2013-11-30
    Publisher:
    American Association for the Advancement of Science (AAAS)
    Print ISSN:
    0036-8075
    Electronic ISSN:
    1095-9203
    Topics:
    Biology
    Chemistry and Pharmacology
    Computer Science
    Medicine
    Natural Sciences in General
    Physics
    Keywords:
    *Access to Information ; Periodicals as Topic/*economics ; Research/*economics
    Published by:
    http://www.aaas.org/

    Latest Papers from Table of Contents or Articles in Press
  2. 2
    Auger, C. J. ; Bentley, G. E. ; Auger, A. P. ; Ramamurthy, M. ; Ball, G. F.

    Oxford, UK : Blackwell Science, Ltd
    Published 2002
    Staff View
    ISSN:
    1365-2826
    Source:
    Blackwell Publishing Journal Backfiles 1879-2005
    Topics:
    Medicine
    Notes:
    In songbirds, the initiation of song behaviour and the neural substrate of this system are highly influenced by gonadal steroids. Receptors for gonadal steroid hormones, such as androgens and oestrogens, have been localized within select nuclei of the song system. An important step in steroid receptor action is the recruitment of nuclear receptor coactivators. The coactivator, cAMP response element binding protein (CREB)-binding protein (CBP), has been implicated in both androgen and oestrogen receptor transactivation. Although the role of CBP in transcriptional mechanisms has been widely studied, little is known about CBP expression in the brain. The association between the distribution of CBP and oestrogen receptors in the hippocampus has been related to long-term memory. However, the distribution of brain CBP has not been related to the expression of gonadal steroid receptors in a system as relevant to reproductive behaviour as the avian song system. Western immunoblotting of European starling (Sturnus vulgaris) brain tissue reveals a band at 265 kDa. Immunohistochemical localization of CBP in starling brain indicates wide, but heterogeneous expression. CBP-immunoreactive (CBP-ir) cells define the boundaries of song control nuclei. In HVc (sometimes called the High Vocal Center) and the robust nucleus of the archistriatum (RA), there is a higher density of CBP-ir cells within the boundaries of these nuclei than in adjacent neostriatum or archistriatum, for HVc and RA, respectively. We also report that the distribution of CBP-ir cells varies among different nuclei within the song control system. CBP-ir cells within area X (also a part of the song system) and HVc are densely packed into clusters, whereas cells can be easily discriminated in RA. CBP is also highly expressed in hypothalamic areas, indicating that areas rich in steroid receptors also contain CBP. These data suggest that CBP is important for modulating transcriptional activities in the song system and other sites in the songbird brain that express gonadal steroid receptors.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1046/j.1365-2826.2002.00842.x

    Articles: DFG German National Licenses
  3. 3
    Ramamurthy, M. K. ; Xu, T. -Y.
    Springer
    Published 1994
    Staff View
    ISSN:
    1436-5065
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Geography
    Physics
    Notes:
    Summary A fine-mesh regional model simulation of upper-level cyclogenesis is carried out to examine the structure and evolution of the accompanying tropopause fold and its relationship to the surface and upper-level cyclones. The initial state for the simulation, conducted using the 80-km, 16-level version of the National Meteorological Center Eta model, uses the Level III-b gridded dataset for 1200 UTC, 18 January 1986, during the First Intensive Observing Period (IOP-1) of the Genesis of Atlantic Lows Experiment (GALE) project. Results are presented from a 48 hour integration of the model. The emphasis is on the examination of the synoptic scale evolution and structure of the upper-level cyclone and tropopause fold, both of which were successfully simulated in the model. The potential vorticity structure associated with a propagating jet-streak displayed distinctive structure, with its tilt reversing as the jet-streak moved around the base of an amplifying upper-level trough. In addition, the model simulates the intrusion of dry, stratospheric air containing high potential vorticity anomalies into the lower troposphere as well as subsidence warming when the folding of the tropopause occurs. the model also predicts upper-level frontogenesis as a result of a thermally indirect secondary circulation in the exit region of the jet-streak. The success of the model simulation is most likely the result of comprehensive physics and the fine grid resolution employed and, more importantly, the excellent distribution of subsynoptic scale initial data during the GALE project.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF01029611

    Articles: DFG German National Licenses
  4. 4
    Navon, I. M. ; Phua, P. K. H. ; Ramamurthy, M.
    Springer
    Published 1990
    Staff View
    ISSN:
    1573-2878
    Keywords:
    Conjugate-gradient methods ; large-scale minimization ; vectorization ; direct minimization ; meteorological problems
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Mathematics
    Notes:
    Abstract During the last few years, conjugate-gradient methods have been found to be the best available tool for large-scale minimization of nonlinear functions occurring in geophysical applications. While vectorization techniques have been applied to linear conjugate-gradient methods designed to solve symmetric linear systems of algebraic equations, arising mainly from discretization of elliptic partial differential equations, due to their suitability for vector or parallel processing, no such effort was undertaken for the nonlinear conjugate-gradient method for large-scale unconstrained minimization. Computational results are presented here using a robust memoryless quasi-Newton-like conjugate-gradient algorithm by Shanno and Phua applied to a set of large-scale meteorological problems. These results point to the vectorization of the conjugate-gradient code inducing a significant speed-up in the function and gradient evaluation for the nonlinear conjugate-gradient method, resulting in a sizable reduction in the CPU time for minimizing nonlinear functions of 104 to 105 variables. This is particularly true for many real-life problems where the gradient and function evaluation take the bulk of the computational effort. It is concluded that vector computers are advantageous for largescale numerical optimization problems where local minima of nonlinear functions are to be found using the nonlinear conjugate-gradient method.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF00940534

    Articles: DFG German National Licenses