ABSTRACT
The formation of a Bose-Einstein condensate of a dilute atomic gas has been studied in situ with a nondestructive, time-resolved imaging technique. Sodium atoms were evaporatively cooled close to the onset of Bose-Einstein condensation and then suddenly quenched to below the transition temperature. The subsequent equilibration and condensate formation showed a slow onset distinctly different from simple relaxation. This behavior provided evidence for the process of bosonic stimulation, or coherent matter-wave amplification, crucial to the concept of an atom laser.
ABSTRACT
Interference between two freely expanding Bose-Einstein condensates has been observed. Two condensates separated by approximately 40 micrometers were created by evaporatively cooling sodium atoms in a double-well potential formed by magnetic and optical forces. High-contrast matter-wave interference fringes with a period of approximately 15 micrometers were observed after switching off the potential and letting the condensates expand for 40 milliseconds and overlap. This demonstrates that Bose condensed atoms are "laser-like"; that is, they are coherent and show long-range correlations. These results have direct implications for the atom laser and the Josephson effect for atoms.
ABSTRACT
Radionuclide ventriculography (RNV) is now a well-established procedure for the noninvasive evaluation of cardiac hemodynamics, including the detection and quantification of valvular regurgitation. 46 patients undergoing aortic or mitral valve replacement were examined by RNV pre- and postoperatively. The specificity of RNV in the diagnosis of aortic or mitral incompetence was high. All cases of moderate to severe aortic regurgitation were identified. This, however, was not true for mitral incompetence. A significant overlap between the left atrium and the left ventricle in the LAO view is held responsible for this decrease in sensitivity. The quantification of aortic regurgitation and the assessment of left ventricular function by RNV appears to hold promise in the preoperative workup. This diagnostic approach yields important additional information, which may be essential in the appropriate timing of surgical intervention. Aortic valve replacement for incompetence as well as for stenosis was accompanied by a significant improvement in global left ventricular ejection fraction. No postoperative change in ejection fraction was found in cases of mitral incompetence, while a slight increase was observed following operative therapy for mitral stenosis. The radioisotope findings were correlated to the results obtained by cardiac catheterization and noninvasive techniques such as echocardiography. The place of RNV in the pre- and postoperative management of valvular heart disease is delineated in this paper. It is of special value in the evaluation of aortic incompetence and may be an important diagnostic adjunct in the approach to the patient with mitral valve disease or aortic stenosis.
