Fluorometric studies of recovery metabolism of rat fast- and slow-twitch muscles

Recovery metabolism of fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus (SOL) muscles of the rat has been investigated using fluorometric monitoring of reduction of nicotinamide adenine dinucleotide (NAD). In both EDL and SOL, groups of twitch contractions produced a decrease in fluorescence (oxidation of NADH) which returned to the resting base line after contraction ceased. These responses proceeded more quickly in EDL than SOL and were abolished by anoxia. A 1-s tetanus of SOL produced an initial reduction which could be abolished with iodoacetate followed by a prolonged oxidation which could be blocked by anoxia. The fluorescence of EDL was decreased immediately following a 1-s tetanus but then rapidly increased well beyond the resting level of reduction and persisted throughout the recovery period. This reduction was largely depressed by iodoacetate. The results indicate marked differences in the recovery metabolism of these muscles, consistent with predominantly mitochondrial oxidative activity in the slow-twitch muscles and predominantly glycolytic activity in the fast-twitch muscles.     

Molecular thermal conductivity of heavy-water vapor at pressures up to 30 MPa and temperatures up to 700°C

The results of an experimental investigation of the molecular thermal conductivity of heavy-water vapor by the method of pulsed heating of a thin wire are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 56, No. 1, pp. 92–97, January, 1989.     

Optimization of diamond grinding conditions for steel R6M5F3 allowing for the process unsteadiness

The paper addresses optimization of machining conditions in diamond grinding of steel R6M5F3 taking into account the process unsteadiness. The optimization is accomplished for plunge-cut grinding by the elastic mode with a constant workpiece-to-wheel pressing force, the kinematics of the process being similar to the rigid-mode one. The region of possible machining conditions for an early stage of the elastic-mode diamond grinding is considered in the coordinates “workpiece speed—workpiece pressing force”. The workpiece speed is determined for a specified machined surface roughness. The workpiece pressing force is chosen to be minimal based on the condition of ensuring no phase-structural transformations in the surface layer of the workpiece material, no diamond oxidation, and no destruction of diamond grits. The process unsteadiness was allowed for through the use of the equations describing the time variation of the current limited cutting ability of the grinding wheel.     

Mass transfer and structure of asbestos and non-asbestos diaphragms for chlorine and caustic production

Models and equations describing aspects of diaphragm performance are discussed in view of recent experiences with non-asbestos diaphragms. Excellent control of wettability and, therefore, of the amount of gases inside the diaphragm, together with chemical resistance to the environment during electrolysis, was found to be an essential prerequisite to performances of non-asbestos diaphragms that are comparable to those of asbestos diaphragms. Equations, derived and supported by experimental evidence from previous work, are shown to describe and predict hydrodynamic permeability and ohmic voltage drop of diaphragms, even in cases where the amount of gases inside the diaphragm slowly increases during electrolysis. Current efficiency is observed to be only dependent to a slight extent on the effective electrolyte void fraction inside the diaphragm. Major effects that determine current efficiency at 2 kA m^–2 and 120 gl^–1 caustic are shown to be diaphragm thickness, pore diameter distribution and the number of interconnections between pores inside the diaphragm. A discussion on design of the structure of non-asbestos diaphragms is presented.Nomenclature B permeability coefficient (m²) - c _i,x concentration of ionic species i at position x (mol m^–3) - c _k concentration of hydroxyl ions in catholyte (mol m^–3) - CE current efficiency - d thickness of diaphragm (m) - thickness of layer (m) - D _i ionic diffusion coefficient of species i (m²s^–1) - D _e dispersion coefficient (m²s^–1) - electrolyte void fraction - E potential inside diaphragm (V) - F Faraday constant, 96487 (C mol^–1 of electrons) - F _j,i flux of ionic species i in the stagnant electrolyte inside small pores of layer j - H hydrostatic head (N m^–2) - i flux of current =j/F (mol m^–2s^–1) - j current density (A m^–2) - k _i,l constant representing diffusion in diaphragm (m²s^–1) - k ₂ constant representing migration in diaphragm (m^–1) - v _p hydraulic pore radius according to [15] (m) - N number of layers - N _j,i flux of ionic species i in layer j (mol m^–2s^–1) - P hydrodynamic permeability (m³ N^–1s^–1) - R gas constant, 8.3143 (J mol^–1 K^–1) - density of liquid (kg m^–3) - R ₀ electric resistivity of electrolyte (ohm m) - R _d electric resistivity of porous structure filled with electrolyte (ohm m) - R _m resistance of the diaphragm (ohm m²) - R _a resistance of anolyte layer (ohm m²) - R _e resistance of electrodes (ohm m²) - s specific surface of porous structure (m^–1) - s ₀ standard specific surface of solids in porous structure (m^–1) - tortuosity defined according toR _d/R ₀=/ - T absolute temperature (K) - u superficial liquid velocity (m s^–1) - U cell voltage (V) - dynamic viscosity (N s m^–2) - v kinematic viscosity (m²s^–1) - x diaphragm dimensional coordinate (m) - y radial coordinate inside pores (m) Paper presented at the meeting on Materials Problems and Material Sciences in Electrochemical Engineering Practice organised by the Working Party on Electrochemical Engineering of the European Federation of Chemical Engineers held at Maastricht, The Netherlands, September 17th and 18th 1987.