Phospholipid fatty acid composition in type I and type II rat muscle

The fatty acid composition of the membrane phospholipids phosphatidylcholine (PC) and phosphatidylethanolamine in insulin-sensitive Type I (soleus) and insulin-resistant Type II (EDL) muscle is not known. In the present studies, soleus and EDL muscles were removed from 250–300 g Sprague-Dawley rats, and the fatty acid composition of total and individual phospholipid (PL) species was quantitated. As expected, triglyceride content was increased twofold in soleus muscle. No quantitative differences in the individual PL species or cholesterol content were found between the two muscles. However, a striking difference in PL fatty acid composition was observed in the PC fraction. An increase in 16∶0 with decreases in 18∶0, 18∶1, 22∶5n-3, and 22∶6n-3 (P<0.001 for each) was observed in the PC fraction of EDL compared to that from soleus, consistent with reduced elongation of PC fatty acids. Inhibition of fatty acid oxidation with the carnitine palmitoyl transferase-1 inhibitor, etomoxir, did not alter the fatty acid pattern in either muscle. We conclude that an alteration in PL fatty acid composition consistent with reduced elongation of both saturated and unsaturated fatty acids is observed in Type II muscle. The restriction of these alterations to the PC fraction has important implications. Deceased (June 28, 1996).     

K- and Cs-FeV/Al2O3soot combustion catalysts for diesel exhaust treatment

Alkali-doped FeV oxide catalysts supported on -alumina were prepared and their catalytic activity in the combustion of diesel soot is reported. The catalysts were characterized by XRD, TPR and SEM–EDX analysis. The influence of the nature of the alkali metal (K and Cs), the temperature of treatment of the catalysts and the stability to sulfur poisoning have been investigated.

Catalysts doped with Cs were the most active and stable also after several combustion cycles and in the presence of sulfur in the stream. The activity measurements and microstructural results suggest that the combustion of soot is favored on catalysts where amorphous phases and/or mixed Fe---V---O phases, ensuring an intimate contact between iron and vanadium, are present. A reaction mechanism involving the participation of the redox couple Fe(II)–Fe(III) in the activation of the vanadium combustion sites, is proposed.     

Straightforward modeling of dynamic I–V characteristics for microwave FETs

This work presents a straightforward approach aimed at modeling the dynamic I–V characteristics of microwave active solid‐state devices. The drain‐source current generator represents the most significant source of nonlinearity in a transistor and, therefore, its correct modeling is fundamental to predict accurately the current and voltage waveforms under large‐signal operation. The proposed approach relies on using a small set of low‐frequency time‐domain waveform measurements combined with numerical optimization‐based estimation of the nonlinear model parameters. The procedure is applied to a gallium nitride HEMT and silicon FinFET. The effectiveness of the modeling procedure in terms of prediction accuracy and generalization capability is demonstrated by validation of the extracted models under operating conditions different than the ones used for the parameters estimation. Good agreement between measurements and model simulations is achieved for both technologies and in both low‐ and high‐frequency range. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:109–116, 2014.     

Reactive Compatibilizer Precursors for LDPE/PA6 Blends, 4

Summary: The effectiveness of some thermoplastic elastomers grafted with maleic anhydride (MA) or with glycidyl methacrylate (GMA) as compatibilizer precursors (CPs) for blends of low density polyethylene (LDPE) with polyamide‐6 (PA) has been studied. The CPs were produced by grafting different amounts of MA or GMA onto a styrene‐block‐(ethylene‐co‐1‐butene)‐block‐styrene copolymer (SEBS) (KRATON G 1652), either in the melt or in solution. A commercially available SEBS‐g‐MA copolymer with 1.7 wt.‐% MA (KRATON FG 1901X) was also used. The effect of the MA concentration and of other characteristics of the SEBS‐g‐MA CPs was also studied. The specific interactions between the CPs and the blends components were investigated through characterizations of the binary LDPE/CP and PA/CP blends, in the whole composition range. It was demonstrated that the SEBS‐g‐GMA copolymers display poor compatibilizing effectiveness due to cross‐linking resulting from reactions of the epoxy rings of these CPs with both the amine and the carboxyl end groups of PA. On the contrary, the compatibilizing efficiency of the MA‐grafted elastomers, as revealed by the thermal properties and the morphology of the compatibilized blends, was shown to be excellent. The results of this study confirm that the anhydride functional groups possess considerably higher efficiency, for the reactive compatibilization of LDPE/PA blends, than those of the ethylene‐acrylic acid and ethylene‐glycidyl methacrylate copolymers investigated in previous works.

SEM micrograph of the 75/25 LD08/PA blend (with 2 phr SEBSMA1).     

Heat Induced Structure Modifications in Polymer‐Layered Silicate Nanocomposites

Summary: The success of the use of layered silicates in polymer nanocomposites, to improve physical and chemical properties is strictly related to a deeper knowledge of the mechanistic aspects on which the final features are grounded. This work shows the temperature induced structural rearrangements of nanocomposites based on poly[ethylene‐co‐(vinyl acetate)] (EVA) intercalated‐organomodified clay (at 3–30 wt.‐% silicate addition) which occur in the range between 75 and 350 °C. In situ high temperature X‐ray diffraction (HT‐XRD) studies have been performed under both nitrogen and air to monitor the modifications of the nanocomposite structure at increasing temperatures under inert/oxidative atmosphere. Heating between 75 and 225 °C, under nitrogen or air, causes the layered silicate to migrate towards the nanocomposite surface and to increase its interlayer distance. The degradation of both the clay organomodifier and the VA units of the EVA polymer seems to play a key role in driving the evolution of the silicate phase in the low temperature range. The structural modifications of the nanocomposites in the high temperature range (250–350 °C), depended on the atmosphere, either inert or oxidizing, in which the samples were heated. Heating under nitrogen led to deintercalation and thus a decrease of the silicate interlayer space, whereas exfoliation was the main process under air leading to an increase of the silicate interlayer space.

Heat induced structural modification of EVA‐clay nanocomposite under nitrogen and air.     

Development of a virtual reality laboratory stressor

Virtual Reality - This research report describes the development of a virtual reality (VR) laboratory stressor to study the effects of exposure to stressful events. The aim of the research was to...     

The corrosion of Co-Nb alloys in reducing/oxidizing-sulfidizing gases at 600–800°C

The corrosion of the two pure metals and of two alloys containing 15 and 30 wt% Nb has been studied at 600–800°C in H₂-H₂S-CO₂ gas mixtures providing 10⁻⁸ atm S₂ at all temperatures and 10⁻²⁴ atm O₂ at 600°C and 10⁻²⁰ atm O₂ at 700 and 800°C. The corrosion kinetics were rather complex, being sometimes parabolic and in other cases nearly linear. Under a constant temperature the addition of niobium generally reduced the corrosion rate, except at 700°C when pure cobalt corroded more slowly than the two alloys. The corrosion rates for the same material decreased with an increase in temperature under the same sulfur pressure. Except at 800°C under 10⁻⁸ atm S₂, which is below the dissociation pressure of cobalt sulfide, the scales presented an outer layer of pure cobalt sulfide and an inner layer of complex composition containing a mixture of double sulfide, niobium oxide and in some cases of unreacted metallic cobalt particles. The addition of niobium was generally beneficial, the effect increasing with its concentration in the alloy, but the corrosion rates of the alloys were still much higher than that of pure niobium, mainly as a result of the lack of formation of a protective layer of niobium sulfide. The corrosion behavior is examined with special reference to the consequences of the low solubility of niobium in cobalt and to the relation between the microstructure of the alloys and the scales.     

An analysis of the internal oxidation of binary M-Nb alloys under low oxygen pressures at 600–800°C

The corrosion of M–Nb alloys based on iron, cobalt, and nickel and containing 15 and 30 wt% Nb has been studied at 600–800°C under low oxygen pressures (10^–24 atm at 600°C and 10^–20 atm at 700–800°C). Except for the Co–Nb and Ni–Nb alloys corroded at 800°C, which formed external scales of niobium oxides, corrosion under low O₂ pressures produced an internal oxidation of niobium. This attack was much faster than expected on the basis of the classical theory. Furthermore, the distribution of the internal oxide in the alloys containing two metal phases was very close to that of the Nb-rich phase in the original alloys. These kinetic, microstructural, and thermodynamic aspects are examined by taking into account the effects of the limited solubility of niobium in the various base metals and of the two-phase nature of the alloys.     

The oxidation of two Fe−Nb alloys under low oxygen pressures at 600–800°C

The oxidation of two Fe–Nb alloys containing 15 and 30 wt.% Nb has been studied at 600–800°C under low oxygen pressures, similar to those prevailing in environments of the coal-gasification type. The reaction produced only an internal oxidation of niobium to form two niobium oxides (NbO₂ and Nb₂O₅) and in some cases a double Fe–Nb oxide. The kinetics of this reaction were very slow at 600°C but rather fast at 700 and 800°C. A peculiar feature of the internal oxidation of these alloys is that the distribution of the internal oxides follows closely that of the Nb-rich phase in the original two-phase alloys. This behavior, as well as the lack of formation of external scales of niobium oxides, is mainly a result of the limited solubility of niobium in iron and of the consequent presence of two metal phases in the alloys.