Modification of the ECAS reference steam power generating plant to comply with the EPA 1979 new source performance standards

Detailed capital cost estimates for the ECAS and modified reference plants in mid-1978 dollars for both 250 and 175 F (394 and 353 K) stack gas reheat temperatures based on the cost estimates developed for the ECAS study are presented. The scope of the work included technical assessment of sulfur dioxide scrubber system design, on site calcination versus purchased lime, reheat of stack gas, effect of sulfur dioxide scrubber on particulate emission, and control of nitrogen oxides

Sedimentation and Flow Through Porous Media: Simulating Dynamically Coupled Discrete and Continuum Phases

We describe a method to address efficiently problems of two-phase flow in the regime of low particle Reynolds number and negligible Brownian motion. One of the phases is an incompressible continuous fluid and the other a discrete particulate phase which we simulate by following the motion of single particles. Interactions between the phases are taken into account using locally defined drag forces. We apply our method to the problem of flow through random media at high porosity where we find good agreement to theoretical expectations for the functional dependence of the pressure drop on the solid volume fraction. We undertake further validations on systems undergoing gravity induced sedimentation.Comment: 22 pages REVTEX, figures separately in uudecoded, compressed postscript format - alternatively e-mail '[email protected]' for hardcopies

On Propagation of Excitation Waves in Moving Media: The FitzHugh-Nagumo Model

BACKGROUND: Existence of flows and convection is an essential and integral feature of many excitable media with wave propagation modes, such as blood coagulation or bioreactors. METHODS/RESULTS: Here, propagation of two-dimensional waves is studied in parabolic channel flow of excitable medium of the FitzHugh-Nagumo type. Even if the stream velocity is hundreds of times higher that the wave velocity in motionless medium (), steady propagation of an excitation wave is eventually established. At high stream velocities, the wave does not span the channel from wall to wall, forming isolated excited regions, which we called "restrictons". They are especially easy to observe when the model parameters are close to critical ones, at which waves disappear in still medium. In the subcritical region of parameters, a sufficiently fast stream can result in the survival of excitation moving, as a rule, in the form of "restrictons". For downstream excitation waves, the axial portion of the channel is the most important one in determining their behavior. For upstream waves, the most important region of the channel is the near-wall boundary layers. The roles of transversal diffusion, and of approximate similarity with respect to stream velocity are discussed. CONCLUSIONS: These findings clarify mechanisms of wave propagation and survival in flow

Diabetic patients produce an increase in coronary sinus endothelin 1 after coronary artery bypass grafting

Diabetes is associated with altered vascular responses, and diabetic patients demonstrate increased morbidity and mortality after coronary artery bypass grafting (CABG). We tested whether endothelin (ET)-1 levels in this patient population differed from those in nondiabetic subjects after CABG. Of 14 consecutive patients who underwent CABG by the same surgeon, 7 had type 2 diabetes and 7 were nondiabetic. The two groups did not differ significantly in preoperative ejection fraction, number of vessels bypassed, cross-clamp time, or Parsonnet\u27s score. Coronary sinus blood samples were obtained before cardioplegic arrest and then obtained at 1 and 15 min after each of two reperfusion periods: reperfusion A (native coronary perfusion plus the left internal mammary artery), reperfusion B (saphenous vein graft perfusion). ET- 1 was significantly increased at all reperfusion time points in diabetic patients compared with nondiabetic patients. In diabetic patients, reperfusion after CABG can trigger the release of ET-1, which may be a contributing factor in the increased cardiac morbidity seen in this patient population

Cardiopulmonary bypass increases coronary IL-8 in diabetic patients without evidence of reperfusion injury

Background. Endothelin-1 (ET-1) has been shown to be a potent agonist for monocyte production of the neutrophil chemotactic cytokine interleukin-8 (IL-8). We have shown that diabetic patients demonstrate elevated coronary ET-1 after coronary artery bypass grafting (CABG). We hypothesized that these same diabetic patients would manifest elevated coronary IL-8 and conjugated diene concentrations (an index of reperfusion injury). Methods. Sixteen patients [9 nondiabetics and 7 type II diabetics] underwent nonemergent CABG. The two groups did not differ significantly in preoperative ejection fraction, number of vessels bypassed, or cross-clamp time. Coronary sinus samples were obtained prior to cardioplegic arrest (baseline) and at 1 and 15 min after reperfusion periods A and B (A, reperfusion of native coronaries + LIMA; B, reperfusion of saphenous vein grafts in addition to native coronary system + LIMA). Plasma samples were analyzed for IL-8 (ELISA) and conjugated dienes (spectrophotometry). Results. Initially after reperfusion, IL-8 in both groups was significantly lower than precardioplegia values. In reperfusion B, only the diabetic group demonstrated a significant increase in IL-8 concentrations at 1 and 15 min compared to nondiabetics. Conjugated diene levels were significantly higher in diabetics at each time point than nondiabetics. Conclusions. This study demonstrates an early decrease in IL-8 in both groups, most likely related to depressed production secondary to hypothermia. The subsequent elevation in IL-8 only in the diabetic group was seen without concomitant conjugated diene elevation. While no evidence of reperfusion injury was demonstrated in this time frame, the elevation of IL-8 in diabetics after CABG may contribute to later infiltration and associated oxidative damage

Elevated coronary endothelin-1 but not Nitric oxide in diabetics during CABG

Background. After coronary artery bypass grafting procedures, a higher incidence of morbidity and mortality has been reported in diabetic patients. We tested whether coronary artery bypass grafting in diabetics affects the endothelin-1 and nitric oxide coronary effluent profile during reperfusion. Methods. Twenty-one consecutive patients (9 with type II diabetes mellitus, 12 non-diabetics) underwent coronary artery bypass grafting by one surgeon. The two groups did not differ in preoperative ejection fraction, Parsonnet score, number of vessels bypassed, or cross-clamp time. Each patient was treated in the same intraoperative manner with single atrial, aortic, and antegrade and retrograde cardioplegia (CPL) cannulas. Cold CPL arrest was by antegrade and retrograde infusion of modified Buckberg CPL solution. Warm CPL solution was infused before reperfusion. Coronary sinus blood samples were obtained for estimation of endothelin-1 and nitrite plus nitrate before CPL arrest and at 1 and 15 minutes after each of 2 reperfusion periods. Results. In diabetics, endothelin-1 was significantly increased at all reperfusion times as compared with non-diabetics. Nitrite plus nitrate levels were significantly higher in patients with diabetes than in those without, but did not change with time in either of the groups. Conclusions. Reperfusion after CPL during coronary artery bypass grafting procedure can trigger the release of endothelin-1 in patients with diabetes mellitus. This may favor increased vascular tone or positive inotropic responses after coronary artery bypass grafting and may contribute to significant cardiovascular consequences in diabetic patients