What periodicities can be found in diffraction patterns of quasicrystals?

The structure of quasicrystals is aperiodic. Their diffraction patterns, however, can be considered periodic. They are composed solely of series of peaks which exhibit a fully periodic arrangement in reciprocal space.

Diffraction analysis of decorated Fibonacci chains in the average unit-cell approach.

A novel approach to diffraction analysis of decorated quasicrystals is discussed. An average unit cell has been constructed for a decorated Fibonacci chain and used for analysis of its diffraction pattern. After some transformation of the scattering vectors, all the diffraction peaks are described by a single envelope function which is characteristic of a given decoration.

Volumetric responses of right and left ventricles during upright exercise in normal subjects.

We evaluated the volumetric responses of the right and left ventricles to upright exercise using two noninvasive methods, first-pass radionuclide angiocardiography and the CO2 rebreathing technique, in nine normal subjects. Right (RV) and left (LV) ventricular ejection fractions, heart rate, and cardiac index were determined at rest and during steady-state exercise on the bicycle ergometer at 50% of maximal O2 consumption. From these data, stroke volume index (SVI), end-diastolic volume index (EDVI), and end-systolic volume index (ESVI) were derived.

Gold-195m for serial first pass radionuclide angiocardiography during upright exercise in patients with coronary artery disease.

Sequential first pass radionuclide angiocardiography can be performed in rapid succession using gold-195m because of its low radiation dose and short half-life (30.5 seconds). In 25 patients with known or suspected coronary artery disease, first pass studies with gold-195m were obtained using a computerized multicrystal gamma camera at rest (n = 29), at the end of each 3 minute stage of exercise (n = 25) and immediately after exercise (n = 23).

Contrasting acute effects of vasodilators (nitroglycerin, nitroprusside, and hydralazine) on right ventricular performance in patients with chronic obstructive pulmonary disease and pulmonary hypertension: a combined radionuclide-hemodynamic study.

Fourteen patients with chronic obstructive pulmonary disease, mild to moderate pulmonary hypertension, and diminished right ventricular (RV) ejection fraction were studied acutely with use of a combined radionuclide-hemodynamic approach to assess and contrast the effects of 3 vasodilators on RV performance and central hemodynamic function. Nitroglycerin significantly decreased mean right atrial pressure, RV end-diastolic volume index, mean pulmonary artery pressure, cardiac index, and arterial oxygen tension, but did not affect pulmonary vascular resistance index and increased RV ejection fraction. Nitroprusside had similar effects on mean right atrial pressure, RV end-diastolic volume index, mean pulmonary artery pressure, cardiac index, and arterial oxygen tension, but also mildly decreased pulmonary vascular resistance index and did not alter RV ejection fraction.