Experimental investigations on graphene oxide/rubber composite thermal conductivity.

Graphene oxide/rubber composites were experimentally investigated for obtaining their thermal properties. Three kinds of the composite matrix material have been used: NBR, HNBR and FKM. The reduced graphene oxide in the form of crumped flakes has been applied as the filler influencing on thermal conductivity of the composites. Two values of graphene oxide weight concentration have been taken into account in the investigation. Thermal conductivity of the composites and basic matrix has been measured by the professional apparatus with the use of the guarded heat plate method. Before measurements the preliminary tests using the simplified comparative method have been performed. The results obtained, both from preliminary tests and using the guarded heat plate method, show an increase in thermal conductivity with increasing the reduced graphene oxide content in the composite. The experimental investigation allowed to determine not only the increase in thermal properties of graphene oxide/rubber composites compared to the basic matrix, but also the absolute values of thermal conductivities. Additionally, the SEM analysis showed that the tested composite samples contain agglomerates of the rGO nanoparticles. The occurrence of agglomerates could affect the composite thermal properties. This was noticed in the comparatively measurements of the temperature of different composites during the heating of samples tested. The maximum enhancement of thermal conductivity obtained was about 11% compared to the basis matrix of the composites tested.

Severe mitral stenosis secondary to eosinophilic granulomatosis resolving after pharmacological treatment.

We present a case of 44-year-old woman who underwent effective pharmacological treatment of severe mitral stenosis. The patient was hospitalized due to rapidly progressive dyspnea. Her medical history included asthma, perennial rhinitis, and nasal polyps. Echocardiography showed a mass of the left ventricle involving the mitral valve; cardiac MRI suggested acute endocarditis. Severe peripheral blood eosinophilia was found. Eosinophilic granulomatosis with polyangiitis was diagnosed; treatment with prednisone and cyclophosphamide was started. Despite the clinical improvement, severe mitral stenosis persisted, surgical treatment was planned. However, evaluation after 6 cycles of cyclophosphamide pulse therapy revealed a significant regression of the valvular disease.