Propane oxidative dehydrogenation on silica based oxide catalysts

The oxidative dehydrogenation of propane to propylene with molecular O₂ (PPD) has been investigated on commercial bare SiO₂ and medium loaded V₂O₅ and MoO₃ catalysts at 450–525°C. The direct relationship between the density of reduced sites (, 10¹⁶ s_r g _cat– ¹ ), evaluated in steady-state conditions by O₂ chemisorption, and the POD reaction rate proves the occurrence of a concerted reaction mechanism involving the activation of gas-phase O₂ on the reduced sites of the catalyst surface. A straight-line correlation between the activity of such silica based catalysts in POD and methane partial oxidation to formaldehyde (MPO) at 525°C has been disclosed.     

Accurate Extraction of Charge Carrier Mobility in 4‐Probe Field‐Effect Transistors

Charge carrier mobility is an important characteristic of organic field‐effect transistors (OFETs) and other semiconductor devices. However, accurate mobility determination in FETs is frequently compromised by issues related to Schottky‐barrier contact resistance, that can be efficiently addressed by measurements in 4‐probe/Hall‐bar contact geometry. Here, it is shown that this technique, widely used in materials science, can still lead to significant mobility overestimation due to longitudinal channel shunting caused by voltage probes in 4‐probe structures. This effect is investigated numerically and experimentally in specially designed multiterminal OFETs based on optimized novel organic‐semiconductor blends and bulk single crystals. Numerical simulations reveal that 4‐probe FETs with long but narrow channels and wide voltage probes are especially prone to channel shunting, that can lead to mobilities overestimated by as much as 350%. In addition, the first Hall effect measurements in blended OFETs are reported and how Hall mobility can be affected by channel shunting is shown. As a solution to this problem, a numerical correction factor is introduced that can be used to obtain much more accurate experimental mobilities. This methodology is relevant to characterization of a variety of materials, including organic semiconductors, inorganic oxides, monolayer materials, as well as carbon nanotube and semiconductor nanocrystal arrays.     

Reduced Biliverdin Reductase-A Expression in Visceral Adipose Tissue is Associated with Adipocyte Dysfunction and NAFLD in Human Obesity

Biliverdin reductase A (BVR-A) is an enzyme involved in the regulation of insulin signalling. Knockout (KO) mice for hepatic BVR-A, on a high-fat diet, develop more severe glucose impairment and hepato-steatosis than the wild type, whereas loss of adipocyte BVR-A is associated with increased visceral adipose tissue (VAT) inflammation and adipocyte size. However, BVR-A expression in human VAT has not been investigated. We evaluated BVR-A mRNA expression levels by real-time PCR in the intra-operative omental biopsy of 38 obese subjects and investigated the association with metabolic impairment, VAT dysfunction, and biopsy-proven non-alcoholic fatty liver disease (NAFLD). Individuals with lower VAT BVR-A mRNA levels had significantly greater VAT IL-8 and Caspase 3 expression than those with higher BVR-A. Lower VAT BVR-A mRNA levels were associated with an increased adipocytes’ size. An association between lower VAT BVR-A expression and higher plasma gamma-glutamyl transpeptidase was also observed. Reduced VAT BVR-A was associated with NAFLD with an odds ratio of 1.38 (95% confidence interval: 1.02–1.9; χ² test) and with AUROC = 0.89 (p = 0.002, 95% CI = 0.76–1.0). In conclusion, reduced BVR-A expression in omental adipose tissue is associated with VAT dysfunction and NAFLD, suggesting a possible involvement of BVR-A in the regulation of VAT homeostasis in presence of obesity.     

Heavy crude oil asphaltenes as a nanofiller for epoxy resin

Asphaltenes are harmful components of heavy crude oils and require rational utilization after oil refining or deasphalting. Asphaltenes are macromolecules containing various functional groups that self-assemble to nanoscale aggregates and can be used as nanofillers for polymers. In this research, mixtures of asphaltenes with the diglycidyl ether of bisphenol A were considered. The solubility of asphaltenes in this epoxy resin, the rheological properties of the mixtures, and the effect of asphaltenes on the curing with 4,4′-diaminodiphenyl sulfone were studied. In addition, the glass transition temperature, strength, and adhesion characteristics of the asphaltene-filled cured composites were evaluated. The dual role of asphaltenes in polymer modification was demonstrated: the asphaltenes simultaneously plasticize and reinforce the polymer matrix, and the transition from predominant plasticization to strengthening occurs with an asphaltene content at 20 wt%. The dual reinforcement/plasticization effect occurs because epoxy composites contain both nanosized and microsized particles of asphaltenes due to the partial dissolution of asphaltenes in the epoxy resin and the decrease in their solubility during high-temperature curing.     

Catalytic 3D polymerization of C60

The present study addresses the problems of catalytic synthesis of C₆₀-based 3D polymers in the presence of carbon disulfide CS₂. It is shown that CS₂ lowers the pressure of fullerite 3D polymerization at room temperature. In particular, the pressure at which the 3D ultrahard fullerite C₆₀ phase is formed decreases from 18 GPa to 7 GPa. The catalyst plays no significant role at room temperature and low pressures up to 6 GPa. When the C₆₀ + CS₂ is heated to 1200 K, the pressure of the 3D C₆₀ polymerization is further reduced to 2–4 GPa. Based on the TEM data, we propose a 3D polymer structure based on C₆₀ obtained by the catalytic synthesis.     

PVC silver zeolite composites with antimicrobial properties

Poly(vinyl chloride) (PVC) composites containing increasing amounts (2–20%, w/w) of silver zeolite (SZ) were prepared by melt mixing and characterized by thermal, mechanical and rheological analyses. The addition of large amount of SZ did not influence the processability and the formability of the composites, if compared to neat plasticized PVC. The antibacterial activity of PVC SZ composites was tested on Escherichia coli and Staphylococcus epidermidis and resulted promising both in culture broth and on agar plate and also in sterile urine seeded with these strains, for simulation purposes. In sterile urine, composites induced a significant reduction (4–6 log units) of viability of both strains already at 24 h, inhibiting E. coli growth up to 20 days, whereas their antimicrobial action against S. epidermidis vanished within 5 days. The silver release in sterile urine was determined up to 20 days. It was found that the highest amount of silver ions was released during the first day (0.365 ppm), whilst from days 6 to 20 the silver release decreased, reaching a steady daily mean value of 0.02 ppm.     

Flavanones in Citrus fruit: Structure–antioxidant activity relationships

Epidemiological surveys have shown an inverse relationship between the intake of fruit and the incidence of coronary heart disease and some type of cancer. Data found in the literature regarding the flavonoids in general while this study focuses on flavanones, a subclass of flavonoids which occurs in Citrus fruit. The aim of this work is to elucidate the antioxidant or pro-oxidant behaviours of some common flavanones and to determine their activity–structure relationships as antioxidant using the crocin bleaching inhibition assay. The compounds studied were regarding both the aglycon form and the glycoside form. Data evidence that the substitution of the 7th OH group of the flavanones by a neohesperidoside influences the relationship between structure and antioxidant activity. In fact, the 3′,4′-catechol structure and the O-methylation, in the aglycone forms, do not result significant. On the other hands, in the glycosylate forms, the 3′,4′-catechol structure noticeably increases the antioxidant power and the O-methylation decreases the antioxidant activity. The influence of the O-glycosylation with a rutinose molecule is neglectable.