Effect of fluid forces on rotor stability of centrifugal compressors and pumps

A simple two dimensional model for calculating the rotordynamic effects of the impeller force in centrifugal compressors and pumps is presented. It is based on potential flow theory with singularities. Equivalent stiffness and damping coefficients are calculated for a machine with a vaneless volute formed as a logarithmic spiral. It is shown that for certain operating conditions, the impeller force has a destablizing effect on the rotor

Sodium and chloride channelopathies with myositis:Coincidence or connection?

Introduction: A proximal myopathy develops in some patients with muscle channelopathies, but the causative molecular mechanisms are unknown. Methods: We reviewed retrospectively all clinical and muscle biopsy findings of 3 patients with channelopathy and additional myositis. Direct DNA sequencing was performed. Results: Pathogenic mutations were identified in each case. Biopsies demonstrated inflammatory infiltrates. Conclusions: Clinicians should consider muscle biopsy in channelopathy patients with severe myalgia and/or subacute weakness and accompanying elevated creatine kinase. Chance association of myositis and channelopathy is statistically unlikely. An alternative hypothesis suggests that inflammatory insults could contribute to myopathy in some patients. Muscle Nerve 44: 283-288, 201