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27 results

Page 1 of 2

  • The hybrid procedure for the borderline left ventricle

  • Christopher K. Davis, Peter Pastuszko, John Lamberti, John Moore, Frank Hanley, Howaida El Said
  • Journal:
    Cardiology in the Young / Volume 21 / Issue 1 / February 2011
    Published online by Cambridge University Press:
    12 November 2010, pp. 26-30
  • Introduction

    In patients with varying degrees of left heart hypoplasia, it is often difficult to determine whether the left heart structures are adequate in size to support biventricular circulation. Historically, the decision to pursue a single ventricle or biventricular repair needed to be made early and was often irreversible. The hybrid procedure may be a better initial approach for patients with borderline left ventricles.

    Methods

    We describe a series of four patients with various congenital cardiac malformations, all of whom had borderline left ventricles. Based on pre-operative echocardiograms, several scoring systems and left ventricle volumes were used to predict the optimal type of repair. A left ventricular volume of 20 millilitres per square metre was used as the minimum cut-off value for adequacy of biventricular repair.

    Results

    The left ventricular volumes for the patients were 17.1, 23.7, 25.4, and 25.8 millilitres per square metre. In none of the four patients were the calculations unanimous in the recommendation to pursue either type of repair. All patients underwent the hybrid procedure and then eventual single ventricle palliation (two patients) or biventricular repair (two patients). All survived with a mean follow-up of 18 plus or minus 3.9 months.

    Conclusions

    The hybrid procedure may be the best option in patients with a borderline left ventricle. It can serve as a bridge to a more definitive repair when patients are older, larger, and for whom the decision between single ventricle and biventricular repair can be more easily made.

  • Convection in a rapidly rotating spherical shell with an imposed laterally varying thermal boundary condition

  • CHRISTOPHER J. DAVIES, DAVID GUBBINS, PETER K. JIMACK
  • Journal:
    Journal of Fluid Mechanics / Volume 641 / 25 December 2009
    Published online by Cambridge University Press:
    10 December 2009, pp. 335-358

  • We investigate thermally driven convection in a rotating spherical shell subject to inhomogeneous heating on the outer boundary, extending previous results to more rapid rotation rates and larger amplitudes of the boundary heating. The analysis explores the conditions under which steady flows can be obtained, and the stability of these solutions, for two boundary heating modes: first, when the scale of the boundary heating corresponds to the most unstable mode of the homogeneous problem; second, when the scale is larger. In the former case stable steady solutions exhibit a two-layer flow pattern at moderate rotation rates, but at very rapid rotation rates no steady solutions exist. In the latter case, stable steady solutions are always possible, and unstable solutions show convection rolls that cluster into nests that are out of phase with the boundary anomalies and remain trapped for many thermal diffusion times.

  • Analysis of phase distributions in the Li2O–Nb2O5–TiO2 system by piezoresponse imaging

  • Albina Y. Borisevich, Sergei V. Kalinin, Dawn A. Bonnell, Peter K. Davies
  • Journal:
    Journal of Materials Research / Volume 16 / Issue 2 / February 2001
    Published online by Cambridge University Press:
    31 January 2011, pp. 329-332
    Print publication:
    February 2001

  • The M-phase solid solutions Li1+x−yNb1−x−3yTix+4yO3) (0.1 ≤ x ≤ 0.3, 0 ≤ y ≤ 0.175) in the Li2O–Nb2O5–TiO2 system have promising microwave dielectric properties. However, these compounds can contain small quantities of ferroelectric impurities that affect the polarization response of the material. Due to their low concentration and their chemical similarity to the host material, the impurities cannot be detected by x-ray diffraction or local elemental analysis. Scanning surface potential microscopy and piezoresponse imaging were used to analyze phase compositions in this system. Piezoresponse imaging demonstrated the presence of thin (<200–300 nm) ferroelectric layers on the grain boundaries oriented along the c-axis of the M-phase. Differences between the surface potential and the piezoresponse of ferroelectric multicomponent systems are discussed.

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