Design of a large network for radiological image data.

Radiological imaging is a rapidly growing business. The field is quickly evolving from films to electronic or digital imaging. By the year 2015, the amount of radiological image data that will have been generated in the U.S. alone is projected to be between 100 and 300 000 PB. (1 PB equals 2(50) B or about 10(15) B.) As the volume of radiological data increases, the need to transmit the data over long distances also increases. For example, radiologists in Chicago, India, or Israel, working in the same medical practice, may read images taken in Chicago. Globally distributed research requires that images be transmitted around the world. Radiologists and researchers want to be able to download files containing hundreds of megabytes in seconds. This service requirement suggests that multiple copies of images should be retained in globally distributed databases to minimize access and transmission delays. Key design issues for such a database include the location of the data repositories relative to the generating and retrieval (reading) sites and the number and location of the copies of the files that are generated. In this paper, we approximate the time to retrieve images stored in city j by a radiologist in city k at time period t. Next, we formulate a model designed to minimize the average retrieval time weighted over all demands. We briefly outline a nested Lagrangian relaxation approach to the problem. Computational results are then summarized. The paper ends with conclusion and directions for future research.     

Effects of eprosartan on renal function and cardiac hypertrophy in rats with experimental heart failure

Activation of the renin-angiotensin system may contribute to the derangement in renal and cardiac function in congestive heart failure. The present study evaluated the effects of eprosartan, a selective angiotensin II receptor antagonist, on renal hemodynamic and excretory parameters and on the development of cardiac hypertrophy in rats with aortocaval fistula, an experimental model of congestive heart failure. Infusion of eprosartan (1.0 mg/kg) in rats with aortocaval fistula produced a significant increase (+34%) in total renal blood flow and a sustained decrease (-33%) in the calculated renal vascular resistance. These effects on renal hemodynamics were more pronounced than those observed in sham-operated control rats and occurred despite a significant fall (-12%) in mean arterial blood pressure. Moreover, eprosartan caused a preferential increase in renal cortical blood perfusion and significantly increased glomerular filtration in rats with congestive heart failure. Chronic administration of eprosartan (5.0 mg/kg per day for 7 days through osmotic minipumps inserted intraperitoneally on the day of operation) resulted in a significant enhancement of urinary sodium excretion compared with nontreated rats with heart failure. Moreover, administration of eprosartan to salt-retaining rats with congestive heart failure resulted in a progressive increase and ultimate recovery in urinary sodium excretion. Finally, early treatment with eprosartan blocked the development of cardiac hypertrophy in rats with aortocaval fistula to a larger extent than the angiotensin-converting enzyme inhibitor enalapril. These findings emphasize the importance of angiotensin II in mediating the impairment in renal function and induction of cardiac hypertrophy in heart failure and further suggest that angiotensin II receptor blockade may be a useful treatment of these consequences in severe cardiac failure.     

Possible involvement of stress-activated protein kinase signaling pathway and Fas receptor expression in prevention of ischemia/reperfusion-induced cardiomyocyte apoptosis by carvedilol

The objectives of this investigation were to evaluate biomechanical factors in the atherosclerotic process using human in vivo hemodynamic parameters and computed numerical simulation qualitatively and quantitatively. The three-dimensional spatial patterns of steady and pulsatile flows in the left coronary artery were simulated, using a finite volume method. Coronary angiogram and Doppler ultrasound measurement of the proximal left coronary flow velocity were performed in humans. Inlet wave velocity distribution obtained from in vivo data of the intravascular Doppler study allowed for input of in vitro numerical simulation. Hemodynamic variables, such as flow velocity, pressure and shear stress of the left anterior descending coronary bifurcation site were calculated. We found that there were spatial fluctuation of flow-velocity and recirculation areas at the curved outer wall of the left anterior descending coronary artery, which were due to the differences of flow-velocity and shear stress, especially during the declaration phase of pulsatile flow. This study suggests that rheologic properties may be a part of the atherogenic process in the coronary bifurcated and curved areas.     

Evaluation of the absorption coefficient for solar radiation in sunspaces and windowed rooms

This paper proposes a simplified model for the evaluation of the solar energy absorbed by a sunspace using an effective absorption coefficient defined as the ratio of the solar energy absorbed by the internal surfaces of the room and the solar energy entering through the glazed surfaces. Reference is made to a simple geometries constituting volumes with glass surfaces of various sizes, number and orientation. In total 10 different geometrical configurations are considered. An extensive parametric analysis is carried out by means of a simulation code with the aim of highlighting the range of variability of the absorption coefficient and the most important variables on which it depends: the latitude, geometrical characteristics of the volume, type of glass, exposure and the optical properties of the opaque surfaces. The results obtained show that the absorption phenomenon can be very adequately parameterized using the simplified models that are proposed.     

Comparison of metoprolol and carvedilol pharmacology and cardioprotection in rabbit ischemia and reperfusion model

Carvedilol, a selective alpha1 and non-selective beta-adrenoceptor antagonist and antioxidant, has been shown to provide significant cardiac protection in animal models of myocardial ischemia. To further explore the mechanisms contributing to carvedilol cardioprotection efficacy, the effects of carvedilol on hemodynamic variables, infarct size and myeloperoxidase activity (an index of neutrophil accumulation) were compared with a beta1-selective adrenoceptor antagonist, metoprolol. Carvedilol (1 mg/kg) or metoprolol (1 mg/kg or 1 mg/kg + 0.5 mg/kg 90 min later) was given intravenously 5 min before reperfusion. In vehicle-treated rabbits, ischemia (60 min) and reperfusion (180 min) resulted in significant increments in left ventricular end diastolic pressure, large infarcts (59+/-2.6% of area-at-risk) and marked increase in myeloperoxidase activity (0.59+/-0.09 U/100 mg tissue). Carvedilol treatment resulted in sustained reduction of pressure-rate-index and significantly smaller infarcts (22.0+/-2.5%, P < 0.01 vs. vehicle) as well as decreased myeloperoxidase activity (0.186+/-0.056 U/100 mg tissue, P < 0.01 vs. vehicle). The highest dose of metoprolol, 1 mg/kg + 0.5 mg/kg, that resulted in pressure-rate-index comparable to that of 1.0 mg/kg carvedilol, failed to reduce myeloperoxidase activity in the ischemic myocardial tissue, and the infarct size (35+/-3.1%) was significantly larger than in carvedilol-treated animals. Taken together, this study suggests that the superior cardioprotection of carvedilol over metoprolol is not a consequence of hemodynamic variances but possibly the result of the additional pharmacological properties of carvedilol such as the antioxidant and anti-neutrophil effects.