No description available.

No description available.

The contribution of left ventricular (LV) torsion and recoil in augmenting stroke volume during exercise is poorly understood. This study examined the effects of aging on LV torsion and recoil at rest and during sub-maximal exercise in 11 young (YU) and 9 older, untrained males (OU), and 12 age-matched older, endurance-trained males (OT) in upright and supine body positions. LV torsion increased from rest to exercise in YU in upright and supine body positions (9.9±2.3 to 13.2±5.2 degrees, p=.03, and 8.8±3.8 to 12.8±6.6 degrees, p=.02, respectively), but not in OU. LV torsion increased with exercise in the supine body position only in OT (p=.046). There were no differences in EDV or change in ESV with supine exercise across groups suggesting that once the Frank-Starling mechanism is fully recruited, the young heart, and that of older, endurance-trained subjects may augment SV by increasing LV torsion and contractility rather than contractility alone.

The contribution of left ventricular (LV) torsion and recoil in augmenting stroke volume during exercise is poorly understood. This study examined the effects of aging on LV torsion and recoil at rest and during sub-maximal exercise in 11 young (YU) and 9 older, untrained males (OU), and 12 age-matched older, endurance-trained males (OT) in upright and supine body positions. LV torsion increased from rest to exercise in YU in upright and supine body positions (9.9±2.3 to 13.2±5.2 degrees, p=.03, and 8.8±3.8 to 12.8±6.6 degrees, p=.02, respectively), but not in OU. LV torsion increased with exercise in the supine body position only in OT (p=.046). There were no differences in EDV or change in ESV with supine exercise across groups suggesting that once the Frank-Starling mechanism is fully recruited, the young heart, and that of older, endurance-trained subjects may augment SV by increasing LV torsion and contractility rather than contractility alone.

Thèse de doctorat : Mathématiques appliquées : Metz : 2001. / Thèse : 2001METZ026S. Bibliogr. en fin de chaque chapitre.

Thesis--M. Phil., University of Hong Kong. / Mimeographed.

published_or_final_version / Civil Engineering / Master / Master of Philosophy

No description available.

No description available.

The thesis is mainly concerned with properties of the concept "σ-purity" introduced by J. Lambek in "Torsion Theories, Additive Semantics and Rings of Quotients", (Springer-Verlag, 1971). In particular we are interested in modul es M for which every exact sequence of the form O→M→K→L→O (or O→K→M→L→O or O→K→L→M→O) is σ-pure exact. Modules of the first type turn out to be precisely the σ- injective modules of O. Goldman (J. Algebra 13, (1969), 10-47). This characterization allows us to study σ- injectivity from the perspective of purity. Similarly the demand that every short exact sequence of modules of the form O→K→M→L→O or O→K→L→M→O be σ-pure exact leads to concepts which generalize regularity and flatness respectively. The questions of which properties of regularity and flatness extend to these more general concepts of σ- regularity and σ-flatness are investigated. For various classes of rings R and torsion radicals σ on R-mod, certain conditions equivalent to the σ-regularity and the σ-injectivity of R are found. We also introduce some new dimensions and study semi-σ-flat and semi-σ-injective modules (defined by suitably restricting conditions on σ-flat and σ-injective modules). We further characterize those rings R for which every R-module is semi- σ-flat. The related concepts of a projective cover and a perfect ring (introduced by H. Bass in Trans. Amer. Math. Soc. 95, (1960), 466-488) are extended in a 'natural way and, inter alia , we obtain a generalization of a famous theorem of Bass. Lastly, we develop a relativized version of the Jacobson Radical which is shown to have properties analogous to both the classical Jacobson Radical and a radical due to J.S. Golan. / Thesis (Ph.D.)-University of Natal, 1992.