Rate Of Recoil Research Articles

Effect of acute human cardiac allograft rejection on left ventricular systolic torsion and diastolic recoil measured by intramyocardial markers.

Left ventricular systolic torsion and diastolic recoil were quantified in 12 human cardiac transplant recipients with surgically implanted intramyocardial markers with the use of computer-aided analysis of biplane cineradiographic images. Measurements were performed between 6 and 16 weeks after surgery and related to the presence or absence of rejection as determined by cardiac biopsy. Torsional deformation, defined as twisting about the left ventricular long axis of the apical region with respect to the base, was characterized in terms of the rate and amplitude of systolic torsion and the rate of diastolic recoil by means of an internal reference system. Comparison of measurements before, during, and after recovery from 14 rejection episodes allowed assessment of the effects of acute reversible cardiomyopathy on left ventricular torsion and recoil. Compared with prerejection values, the amplitude of torsional deformation in the maximally deforming segment (theta max) decreased by 25% from 21.1 +/- 15.2 to 16.0 +/- 5.7 degrees (p less than .005) during acute rejection with myocyte necrosis; this was associated with significant (p less than .05) decreases in the peak systolic torsion rate (+d theta/dtmax), whereas the peak diastolic recoil rate (-d theta/dtmax) was unchanged. This suggests that the stiffness of elastic components of the myocardium may have increased, maintaining the rate of diastolic recoil when these elements are stretched less. With successful treatment of rejection episodes, the torsional deformation characteristics normalized. Heart rate, mean arterial pressure, left ventricular end-diastolic volume, stroke volume, ejection fraction, and peak left ventricular filling rate were unchanged with rejection episodes, whereas left ventricular end-systolic volume increased (p less than .05) during acute rejection and returned to normal with resolution of the rejection process. These data suggest that left ventricular torsional deformation amplitude and rate are sensitive to episodes of subclinical left ventricular dysfunction and that such intramyocardial marker techniques may provide new insights regarding the elastic properties of the ventricular myocardium and their impact on left ventricular mechanics.

Sublimation study of triphenyl boron and the bond-dissociation enthalpy of BC 6H 5

The sublimation pressures of triphenyl boron, B(C 6H 5) 3, in the temperature range 340 to 380 K have been determined from simultaneous measurements of the rate of mass effusion and torsional recoil. The measured vapor pressures expressed by the equations: log 10( p K p 0 )=(9.52±0.07)−(5.326±0.026)×10 3( K T ) log 10( p τ p 0 )=(10.08±0.06)−(5.518±0.022)×10 3( K T ) where p K and p t are the pressures measured by the Knudsen effusion and torsional recoil techniques, respectively, and p o = 101.325 kPa, confirm that triphenyl boron is a monomer in the vapor phase in the temperature range of the measurements. The mean standard molar enthalpy and entropy of sublimation ( p c = 101.325 kPa) derived from these equations are: Δ sub H m o{B(C 6H 5) 3, cr, 360 K} = (103.8 ± 2.5) kJ·mol −1 and Δ sub S m o{B(C 6H 5) 3, cr, 360 K} = (187.6 ± 7.6) J·K −1·mol −1. The mean molar bond-dissociation enthalpy < D>(BC 6H 5) is calculated to be (459 ± 11.6) kJ·mol −1.