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Biomedical subjects

A Soffer

Publications and source records attributed to A Soffer.

At least 19 recordsLinked to original sources
PubMed2005

Theory of nonlinear dispersive waves and selection of the ground state.

A theory of time-dependent nonlinear dispersive equations of the Schrödinger or Gross-Pitaevskii and Hartree type is developed. The short, intermediate and large time behavior is found, by deriving nonlinear master equations (NLME), governing the evolution of the mode powers, and by a novel multitime scale analysis of these equations. The scattering theory is developed and coherent resonance phenomena and associated lifetimes are derived. Applications include Bose-Einstein condensate large time dynamics and nonlinear optical systems. The theory reveals a nonlinear transition phenomenon, "selection of the ground state," and NLME predicts the decay of excited state, with half its energy transferred to the ground state and half to radiation modes. Our results predict the recent experimental observations of Mandelik et al. in nonlinear optical waveguides.

Journal Article↗
PubMed1995

Correspondence of left ventricular ejection fraction determinations from two-dimensional echocardiography, radionuclide angiography and contrast cineangiography.

OBJECTIVES: This study assessed the agreement of left ventricular ejection fraction determinations from two-dimensional echocardiography, radionuclide angiography and contrast cineangiography. BACKGROUND: Previously published reports suggest that two-dimensional echocardiography, radionuclide angiography and contrast cineangiography are equally acceptable methods of assessing left ventricular ejection fraction on the basis of high coefficients of correlation. However, correlation of methods does not necessarily imply agreement. METHODS: In a prospective analysis, 25 consecutive subjects all had two-dimensional echocardiography and radionuclide angiography performed within 10 days of each other in the cardiology department of metropolitan community hospital. A retrospective computer search (Medline) revealed seven studies, using the coefficient of correlation (r), comparing two-dimensional echocardiographic left ventricular ejection fraction (n = 268) with radionuclide angiographic (n = 174) or contrast cineangiographic (n = 119) left ventricular ejection fractions. RESULTS: The eight individual studies (n = 293) comparing two-dimensional echocardiography with either radionuclide angiography or contrast cineangiography exhibited coefficients of correlation ranging from 0.78 to 0.93. Agreement analysis using the method of Bland and Altman was performed by averaging the results obtained from the two techniques and determining how disparate any single ejection fraction was (with 95% confidence limits) from the mean value. Agreement ranged from 23% to 42% around the mean ejection fraction. The average lack of agreement between the two methods for all studies involved was 17%, with an average r value of 0.86. CONCLUSIONS: Left ventricular ejection fraction determinations by means of two-dimensional echocardiography, radionuclide angiography and contrast cineangiography exhibit high correlation and only moderate agreement. High correlation does not always imply high agreement. These results suggest that, when validated by agreement analysis, multiple studies may not be necessary in appropriate clinical situations, potentially reducing costs.

Adult↗
PubMed1991

Isolated significant left main coronary artery stenosis: angiographic, hemodynamic, and clinical findings in 16 patients.

Among 21,545 adult patients who underwent consecutive coronary angiography, 16 (0.07%) were found during their coronary arteriography to have a significant isolated stenotic lesion (luminal diameter narrowing of 50% or more) located at the left main coronary artery. The remaining major epicardial coronary arteries and their branches were free of disease. A strong predilection for the isolated lesion to occur at the ostium of the left main artery was found (12 patients). The most common presenting symptom was angina of less than 4 weeks' duration, although one third of the group was asymptomatic. Resting electrocardiograms were normal in 12 patients, while three patients had T wave inversion and another had nonspecific ST-T changes. Eleven patients exhibited severe stenosis, with eight having 70% to 89% stenosis and three having 90% to 95% stenosis. Five patients had 50% to 69% stenosis. No significant differences were found between patients with angina and patients without angina with respect to age, left ventricular end-diastolic pressure, left ventricular ejection fraction, and mean percent stenosis of the obstructive lesion. Despite the severity and the crucial location of the obstructive lesion, most patients with an isolated, significant left main stenosis appear to have a preserved left ventricular ejection fraction, normal wall motion, and no significant alteration of the left ventricular end-diastolic pressure.

Adult↗
PubMed1991

Complete left main coronary artery occlusion: angiographic evaluation of collateral vessel patterns and assessment of hemodynamic correlates.

An angiographic study of eight patients with total occlusion of the left main coronary artery identified six patients with chronic occlusion and two with acute complete occlusion. In each of six patients, there were two to six different intercoronary collateral pathways. Altogether, a total of 13 specific collateral channels were recognized. One patient had evidence of unique homocollaterals represented by enlarged vasa vasorum, which created a vascular cuff that surrounded a totally obstructed left main artery. The ventricular function and hemodynamic parameters in these patients not only depend on the collateral vessels but may also be affected by the severity of coronary artery disease in the artery that supplies collaterals.

Aged↗
PubMed1991

Absent left main coronary artery: angiographic findings in 83 patients with separate ostia of the left anterior descending and circumflex arteries at the left aortic sinus.

Among 20,332 adult patients who underwent consecutive cardiac catheterization and coronary arteriography, 83 (0.4%) were angiographically identified as having an absent left main coronary artery. The angiographic characteristics of this coronary anomaly include: (1) the presence of two well-separated coronary ostia at the left aortic sinus resulting in separate origin of the left anterior descending and circumflex arteries; (2) an increased incidence of left coronary dominance; (3) a higher (6%) than usual (0.5% to 1.5%) incidence of myocardial bridging; (4) lack of a high incidence of congenital heart anomalies; and (5) an incidence of atherosclerotic coronary artery disease similar to that of patients whose left main artery is intact. In 39% of the patients difficulties in selectively cannulating the separate ostium of the circumflex artery and adequately opacifying this vessel resulted in a need to change the diagnostic catheter size. Recognition of this coronary anomaly is needed to ensure accurate angiographic interpretation and is important for patients undergoing cardiac surgery to selectively perfuse these separate vessels during cardiopulmonary bypass.

Cardiac Catheterization↗
PubMed1989

Demography and the shaping of Israel's borders.

"This paper will show that the demographic map of the Land of Israel in its present form is essentially the principal factor in shaping the extent of Jewish settlement in this generation, and that there is little possibility of changing this pattern except for making small and insignificant adjustments." The author describes the changing demographic picture in Palestine from the late nineteenth century to the present day, particularly changes in the ethnic composition of the population. He concludes that the presence of a majority Arab population in the Occupied Territories of Judea, Samaria, and the Gaza Strip will oblige Israel to compromise with regard to granting cultural and political autonomy. Furthermore, three large Arab enclaves in Israel proper--Galilee, the triangle, and the Bedouin Negev--will have to be given up if current settlement patterns do not radically change, which is itself unlikely.

Asia↗