Nitrogen dioxide effect in the reduction of nitric oxide by propane in oxidizing atmosphere

The role of nitrogen dioxide in the selective reduction of NO by propane over a Cu-MFI zeolite is investigated. NO₂ and NO reductions were carried out under similar conditions of reaction. In the presence of oxygen, the reduction of NO by C₃H₈ does not differ significantly from that of NO₂. In the absence of oxygen, the reduction of NO₂ by propane occurs with a partial decomposition of the nitric dioxide molecule. Such a decomposition leads to the formation of oxygen, which is responsible for the increase in catalytic activity by comparison with the same reaction performed with NO. NO₂ formed and released in the gas phase during the reduction of NO by propane in the presence of oxygen does not play a predominant role in the catalytic process.     

High-power InP MISFETs

InP MISFETs with SiO2 as the gate insulator and a deep channel recess have been fabricated. At 9 GHz the highest power output with 4 dB gain was 3.5 W/mm gate width with 33% power added efficiency. This power is more than twice that of the best GaAs MESFET.     

Physico-chemical modifications of superficial regions of low-density polyethylene (LDPE) film under corona discharge

Using e.s.r., ATR and d.s.c., data on the chemical and structural superficial modifications of LDPE films under corona discharge in the presence of air have been obtained. The results show that the electrical discharge creates superficial ethylenic bonds (1630 cm^?1) and carbonyl groups (1720 cm^?1), the amount of which varies inversely with the main power supply. The treated samples when stored in the presence of light and air undergo marked structural and chemical changes. Formation of a thin waxy layer rich in 〉 CO and 〉 CC 〈 bonds with almost total absence of CH₂CH₂ groups characteristic of LDPE is observed.     

High-mobility Ga0.47In0.53As thin epitaxial layers grown by MBE, very closely lattice-matched to InP

Thin epitaxial layers (< 1.5 ?m) of Ga0.47In0.53As were grown by molecular beam epitaxy, very closely lattice-matched to InP, despite a nonrotating substrate holder. Hall mobilities were measured as a function of temperature in the dark and on illumination. At low temperature, the peak mobility of undoped layers lies between 35000 and 40000 cm2V?1s?1 in the dark and increases up to 45000 cm2V?1s?1 when measured in the light. Preliminary results obtained on slightly Sn-doped layers are also reported.     

Measurements of Oxygen Species Available in PtRh/CeO2–Al2O3 Type Industrial Catalysts and Relationship with Their Three-Way Catalytic Activity

Measurements of the oxygen storage capacity (OSC) were performed on several aged PtRh/CeO₂–Al₂O₃ industrial catalysts, using different techniques, i.e., TPR experiments, O₂ and H₂/O₂ chemisorption. The obtained OSC values were compared to the catalytic activity measured at 723 K in the simultaneous elimination of CO, C₃ hydrocarbons and NO. The best correlation was found for the OSC measured by O₂ chemisorption at 298 K on the solids previously reduced at 573 K and which represents the most reactive oxygen atoms of the catalyst surface.     

Dynamic O-GlcNAcylation of the small heat shock protein alpha B-crystallin

alphaB-Crystallin, originally described as a structural lens protein, is now known to be a member of the small heat shock protein family and is expressed in a number of nonlens tissues. This highly conserved 20 kDa protein aggregates with homologous proteins, including alphaA-crystallin and the small heat shock protein HSP28, to form large heteromeric complexes. Recently, Roquemore et al. (1992) have established that both phosphorylated and unphosphorylated forms of lens alphaB-crystallin are modified with O-linked N-acetylglucosamine, a dynamic posttranslational modification abundant on nuclear and cytoplasmic proteins. In this paper, we have identified the major site of O-GlcNAcylation on lens alphaB as Thr 170. We have further shown that this modification is not restricted to lens alphaB-crystallin but occurs on alphaB isolated from rat heart tissue and human astroglioma cells. Two-dimensional electrophoresis of rat heart alphaB-crystallin revealed two O-GlcNAcylated forms with mobilities corresponding to the unphosphorylated form (alphaB2) and an unidentified, slightly more acidic form. Phosphorylated alphaB-crystallin (alphaB1) was not detected in the rat heart preparation. The major O-GlcNAcylation site on alphaB-crystallins from rat heart also appears to be at Thr 170. Metabolic pulse-chase labeling studies of U373-MG astroglioma cells indicated that turnover of the carbohydrate on alphaB-crystallin is not static but proceeds many-fold more rapidly than turnover of the protein backbone itself, consistent with a regulatory role for O-GlcNAc on this small heat shock protein.     

Mechanical properties of autoclaved shell-aggregate

Waste solid propylene oxide sludge (POS) and fly ash were used as main raw material to prepare propylene oxide sludge aggregate (POSA) under the condition of autoclaved (180 ℃,1.0 MPa) curing. Three different test methods namely cylinder compressive strength (CCS), individual aggregate compressive strength (IACS) and strength contribution rate (SCR) proposed were used to characterize the mechanical properties of the autoclaved POSA. POS shell-aggregate with SCR of 94% were prepared under the hydrothermal synthesis and autoclaved curing. The experimental results indicate that CCS and IACS have good consistency in characterizing mechanical properties of POSA. It is suggested that SCR not only can characterize the strength of POSA core, but also can reflect the effect of shell on the performance of POSA. By means of least square method, relationships between CCS and IACS, CCS and SCR, IACS and SCR were deduced.     

First steps on asynchronous lattice-gas models with an application to a swarming rule

Lattice-gas cellular automata are often considered as a particular case of cellular automata in which additional constraints apply, such as conservation of particles or spatial exclusion. But what about their updating? How to deal with non-perfect synchrony? Novel definitions of asynchronism are proposed that respect the specific hypotheses of lattice-gas models. These definitions are then applied to a swarming rule in order to explore the robustness of the global emergent behaviour. In particular, we compare the synchronous and asynchronous case, and remark that a paradoxical phenomenon, the anti-alignment of particles, is no longer observed when a small but not infinitesimal amount of asynchronism is added.     

In vitro lipolysis tests on lipid nanoparticles: comparison between lipase/co-lipase and pancreatic extract

Solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLC) are lipid nanocarriers aimed to the delivery of drugs characterized by a low bioavailability, such as poorly water-soluble drugs and peptides or proteins. The oral administration of these lipid nanocarriers implies the study of their lipolysis in presence of enzymes that are commonly involved in dietary lipid digestion in the gastrointestinal tract. In this study, a comparison between two methods was performed: on one hand, the lipase/co-lipase assay, commonly described in the literature to study the digestion of lipid nanocarriers, and on the other hand, the lipolysis test using porcine pancreatic extract and the pH-stat apparatus. This pancreatic extract contains both the pancreatic lipase and carboxyl ester hydrolase (CEH) that permit to mimic in a biorelevant manner the duodenal digestive lipolysis. The test was performed by means of a pH-stat apparatus to work at constant pH, 5.5 or 6.25, representing respectively the fasted or fed state pH conditions. The evolution of all acylglycerol entities was monitored during the digestion by sampling the reaction vessel at different time points, until 60?min, and the lipid composition of the digest was analyzed by gas chromatography. SLN and NLC systems obtained with long-chain saturated acylglycerols were rapidly and completely digested by pancreatic enzymes. The pH-stat titration method appears to be a powerful technique to follow the digestibility of these solid lipid-based nanoparticles.