Electrical conductivity and Raman imaging of double wall carbon nanotubes in a polymer matrix

Raman spectroscopy is used to access the dispersion state of DWNTs in a PEEK polymer matrix. The interaction of the outer tube with the matrix can be determined from the line shape of the Raman G band. This allows us to distinguish regions where the nanotubes are well dispersed and regions where the nanotubes are agglomerated. The percolation threshold of the electrical conductivity of the double wall carbon nanotubes (DWNTs)/PEEK nanocomposites is found to be at 0.2-0.3 wt%. We find a maximum electrical conductivity of 3 × 10⁻² S cm⁻¹ at 2 wt% loading. We detect nanotube weight concentrations as low as 0.16 wt% by Raman spectroscopy using a yellow excitation wavelength. We compare the Raman images with transmission electron microscopy images and electrical conductivity measurements. A statistical method is used to find a quantitative measure of the DWNTs dispersion in the polymer matrix from the Raman images.     

Multifunctional pneumatic vortex elements with a rotating vortex generator

Multifunctional pneumatic vortex elements are considered. The basic parameters are established, and a calculation method is proposed.     

Evaporation rate of concentrated electrolyte solutions from fine capillaries

Solution concentration at the meniscus is elevated above the initial value, but does not vary during evaporation from capillaries. The reduction in evaporation rate as compared to water determined experimentally is in agreement with previously developed theory.Notation mass of a mole of water, g/mole - D diffusion coefficient of vapor through air, cm²/sec - relative vapor pressure in chamber (relative air humidity) - M relative vapor pressure above meniscus - density of water, g/cm³ - R gas constant, erg/mole·deg - T temperature, °K - D_* diffusion coefficient for molecules in solution, cm²/sec Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 37, No. 5, pp. 849–853, November, 1979.     

The mechanism of carbon dioxide hydrogenation on copper and nickel catalysts

The mechanism of the reaction of CO₂ with H₂ on copper and nickel catalysts was studied by means of isotope, non-steady-state, and steady-state methods. Staged schemes of the process were proposed. The slow step of CO formation on the test catalysts is the reaction of the adsorbed carboxylate complex with a hydrogen atom. It was shown that hydrogen adsorption on the copper catalyst is dissociative in character. A formyl complex and hydrogen are involved in the slow step of methane formation on the nickel catalyst. It was found that the methane formation proceeds via a consecutive scheme through CO.     

The effect of twin screw extrusion on structural,electrical, and rheological properties in carbon nanotube poly‐ether‐ether‐ketone nanocomposites

The influence of twin screw extruder dispersion of multiwalled carbon nanotubes (CNTs) on the structural, electrical, and rheological properties in poly(ether ether ketone) is studied. Intermediate rotational speeds (200 rpm) of co‐rotating twin screws yield higher electrical conductivity and dynamic shear modulus than for lower or higher speeds when using 3 wt % multiwall CNTs. These improved properties at intermediate speeds are correlated with the dispersion state of nanotubes in the polymer matrix by using transmission electron microscopy and multispectral Raman mapping. We find that the complex shear modulus near structural percolation depends on the dispersion of the CNTs and the residence time in the extruder plays an important role in the final properties of the nanocomposite. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Chronic Ouabain Prevents Na,K-ATPase Dysfunction and Targets AMPK and IL-6 in Disused Rat Soleus Muscle

Sustained sarcolemma depolarization due to loss of the Na,K-ATPase function is characteristic for skeletal muscle motor dysfunction. Ouabain, a specific ligand of the Na,K-ATPase, has a circulating endogenous analogue. We hypothesized that the Na,K-ATPase targeted by the elevated level of circulating ouabain modulates skeletal muscle electrogenesis and prevents its disuse-induced disturbances. Isolated soleus muscles from rats intraperitoneally injected with ouabain alone or subsequently exposed to muscle disuse by 6-h hindlimb suspension (HS) were studied. Conventional electrophysiology, Western blotting, and confocal microscopy with cytochemistry were used. Acutely applied 10 nM ouabain hyperpolarized the membrane. However, a single injection of ouabain (1 µg/kg) prior HS was unable to prevent the HS-induced membrane depolarization. Chronic administration of ouabain for four days did not change the α1 and α2 Na,K-ATPase protein content, however it partially prevented the HS-induced loss of the Na,K-ATPase electrogenic activity and sarcolemma depolarization. These changes were associated with increased phosphorylation levels of AMP-activated protein kinase (AMPK), its substrate acetyl-CoA carboxylase and p70 protein, accompanied with increased mRNA expression of interleikin-6 (IL-6) and IL-6 receptor. Considering the role of AMPK in regulation of the Na,K-ATPase, we suggest an IL-6/AMPK contribution to prevent the effects of chronic ouabain under skeletal muscle disuse.