Multilayer Coextrusion of Polymer Composites to Develop Organic Capacitors

Multilayer coextrusion is applied to produce a tape containing layers of alternating electrical properties to demonstrate the potential for using coextrusion to manufacture capacitors. To obtain the desired properties, we develop two filled polymer systems, one for conductive layers and one for dielectric layers. We describe numerical models used to help determine the material and processing parameters that impact processing and layer stability. These models help quantify the critical ratios of densities and viscosities of the two layers to maintain stable layers, as well as the effect of increasing the flow rate of one of the two materials. The conducting polymer is based on polystyrene filled with a blend of low-melting-point eutectic metal and nickel particulate filler, as described by Mrozek et al. (2010). The appropriate concentrations of fillers are determined by balancing measured conductivity with processability in a twin screw extruder. Based on results of the numerical models and estimates of the viscosity of emulsions and suspensions, a dielectric layer composed of polystyrene filled with barium titanate is formulated. Despite the fact that the density of the dielectric filler is less than the metallic filler of the conductive phase, as well as rheological measurements that later showed that the dielectric formulation is not an ideal match to the viscosity of the conductive material, the two materials can be successfully coextruded if the flow rates of the two materials are not identical. A measurable capacitance of the layered structure is obtained.

Internal mammary artery graft function is not affected in hypertensive patients on therapy

Results are presented which assess the reactivity of isolated human internal mammary artery fragments from non-hypertensive and treated hypertensive patients in vitro. Material from three patient groups was examined: group I, no hypertension; group II, arterial hypertension treated with ACE inhibitors; and group III, arterial hypertension treated with nifedipine. Responses to KCl, norepinephrine and acetylcholine, as well as the influence of N(G)-monomethyl-L-arginine (L-NMMA) on the effects of norepinephrine were tested. Response to KCl was highest in group III, while the contractile reactivity to norepinephrine was depressed in group II. Relaxation after acetylcholine was enhanced in groups II and III. Incubation of vessel fragments with L-NMMA sensitized the tissue to norepinephrine in the order of potency group II>group III>group I. Internal mammary artery function as the graft, and particularly in terms of endothelial function, is not adversely affected in arterial hypertension, although proper antihypertensive treatment may be essential.

Gastric tonometry as a method of visceral oxygenation monitoring in patients undergoing coronary revascularisation

OBJECTIVE

The aim of the study was to assess gastric mucosal pH during certain parts of a major cardiac procedure (hypo- and normothermic), and then throughout the first postoperative day.

METHODS

Gastric mucosal pH was measured using a tonometer, in 15 patients subjected to elective CABG procedures. The patients were also assessed haemodynamically and serum lactate concentrations were measured.

RESULTS

It was found that cardiopulmonary bypass did not suppress visceral perfusion. The most critical was the period between 4th and 12th postbypass hour when a tendency towards decreased cardiac output and oxygen delivery was noted. At the same time oxygen consumption was increasing which resulted in triggering of anaerobic metabolic pathways, that was mirrored by significant rise in serum lactate levels. During this period of time the lowest, although not critical levels of gastric mucosal pH were recorded, suggesting a relative decrease in splanchnic perfusion.

CONCLUSION

Extracorporeal circulation does not significantly compromise splanchnic perfusion. Tonometry is a valuable, non-invasive method of visceral oxygenation monitoring. The first postoperative day is an especially critical time for a cardiac patient--a frequent control of haemodynamic and acid-base balance parameters is absolutely mandatory.

Reactivity of isolated human right atria to norepinephrine in various disease states

The reactivity of isolated, electrically driven, right human atrial muscle to norepinephrine was studied in patients with coronary heart disease, with and without proximal right coronary artery occlusion, and in patients with mitral valve disease. The dose-effect curves for norepinephrine and ED50 doses for each group were compared. We found no difference in reactivity of atria from both coronary artery disease groups. The mitral valve disease group dose-effect curve was shifted to the right (potency ratio 3.98), and the maximal effect was significantly higher than in both coronary artery disease groups. We suggest that adrenoreceptor down regulation could account for observed ED50 difference. The difference in maximal responses could depend on more effective contraction mechanism in mitral valve disease myocardium. We conclude that occlusion of proximal right coronary artery does not necessarily mean ischaemia of right atrium and/or ischaemia does not change myocardium reactivity to norepinephrine.

Nursing theory applications: a practice model

A theoretical model derived from the open system nursing principles of Parse, Newman, and Rogers guided the development of a nursing practice application designed to promote the health and quality of life of hospitalized, chronically mentally ill patients. The harmonious accord model, which consists of the concepts of value, movement, and creative expression patterns and operationalizes these concepts in specific nursing assessment and intervention strategies, was implemented on two extended psychiatry units over a 3-year period. This article discusses practice applications of the model, describes the plan for implementation and patient/nurse responses to implementation, and suggests a line of inquiry to eventually evaluate the effectiveness of the model for increasing patient quality of life.