The state of Tin on Pt–Sn/Nb2O5 catalysts

The effect of tin addition on niobia supported catalysts was studied and compared to the properties of alumina supported bimetallic Pt–Sn catalysts. The catalyst surfaces were probed by methylcyclopentane conversion, showing that both the presence of Sn and the reduction of the support caused a decrease in hydrogenolysis activity, favoring the ring enlargement reaction. The thermodynamics of reduction of these systems, evaluated by following the reduction step (temperature programmed reduction — TPR) with a differential scanning calorimeter (DSC), and irreversible H₂ and CO uptakes, allowed to conclude that a Pt–Sn alloy is formed on niobia supported catalysts.     

The structural characterization and hydroformylation activity of the tri-rhodium complex [Rh3(μ2-dppm)2(μ2-CO)3(K-CO)3]BF4

Rh₂(cod)₂(μ₂-dppm)(μ₂-Cl)]BF₄ (1) rearranges under carbon monoxide to give [Rh₃(μ₂-dppm)₂(μ₂-CO)₃(K¹-CO)₃]BF₄ (2). Complex 2 has been structurally characterized by single crystal X-ray crystallography. The hydroformylation activities of 1 and 2 were compared for substrates styrene and 1-hexene and the activity of 2 found to be unexpectedly high.     

Guanine and plasmid DNA binding of mono- and trinuclear fac-[Re(CO)3]+ complexes with amino acid ligands

We have synthesized and fully characterized four new complexes comprising the fac-[Re(CO)3]+ moiety and the ligands NH3, L-proline (Pro), or N,N-dimethylglycine (dmGly). The reaction of [Re(H2O)3(CO)3]+ with the two amino acids gives trinuclear complexes of general formula [Re(L)(CO)3]3 (where L = amino acid). We have studied the in vitro behavior of these compounds with guanine and DNA in order to understand whether the cytotoxicity exhibited by certain rhenium complexes based on the fac-[Re(CO)3]+ core is due to the formation of nucleobase complexes and inter- or intrastrand links between DNA bases. We have performed model studies with guanine and studied the structural effects induced by different rhenium(I) tricarbonyl complexes on PhiX174 plasmid DNA by electrophoretic methods. Our results show that rhenium complexes with two available coordination sites interact with plasmid DNA to form a stable adduct that is likely to involve two bases.     

Combined Treatment with Dif1stat<Superscript>®</Superscript> and Diet Reduce Plasma Lipid Indicators of Moderate Hypercholesterolemia More Effectively than Diet Alone: A Randomized Trial in Parallel Groups

An open-labeled randomized trial with parallel groups was carried out to study the effects of Dif1stat^® (Monascus purpureus–Linear aliphatic alcohols–Niacin) in the treatment of primary moderate hypercholesterolemia. The trial lasted 8 months. The patients, males and females, were assigned to two groups: A (#130), treated with diet, and B (#110) submitted to diet + Dif1stat^®. After 4 months, group A did not show significant changes in Total cholesterol (TC), LDL-cholesterol (LDLC), HDL-cholesterol (HDLC) or non-HDL-cholesterol (non-HDLC). The same group, showed a reduction in TC (–22%), LDLC (–30%) and non-HDLC (–27%) after 8 months (P ≤ 0.001). After 4 months, TC (–21.3%), LDLC (–29%), and non-HDLC (–26%) were significantly lowered in group B (P ≤ 0.001). In group B, TC, LDLC and non-HDLC showed a further reduction after 8 months: –29.4, –38 and –37%, respectively (P ≤ 0.001). Even triglycerides (TG) decreased significantly (–33%) (P ≤ 0.001). After 8 months, group B showed a significant reduction of TG (–33%) (P ≤ 0.001), when compared to group A. Some safety parameters were significantly reduced in both groups: AST and γ-GT in group A after 4 and 8 months, as well as ALT, AST and γ-GT in group B after 8 months (P ≤ 0.001). Dif1stat^®, given with a suitable diet, was well tolerated in the long-term and induced an anti-atherogenic plasma lipid and lipoprotein profile, in patients with moderate hypercholesterolemia.     

Impedance spectroscopy on porous materials: A general model and application to graphite electrodes of lithium-ion batteries

Electrochemical impedance spectroscopy (EIS) was applied to porous negative graphite electrodes for lithium-ion batteries in the EC:DMC, 1 M LiPF₆ electrolyte. The effect of porosity on the electrode response time was studied and a theoretical model was developed, based on free path of the current lines between subsequent reaction sites. The effect of porosity on the electrode response is evidenced by the impedance spectra in which the high frequency capacitive semicircle is distorted. Fresh electrodes (before the formation of the solid electrolyte interphase, SEI) and cycled electrodes have different shapes of the impedance spectra indicating a change of processes at the surface. In particular, the shape of the spectrum for a fresh electrode can be related to an adsorption process. Impedance spectra of fresh electrodes were fitted using a simple model that considers porosity and the assumed electrochemical processes, giving good agreement between model and data. A correlation was found between adsorption sites and irreversible charge capacity in the first cycle.     

Direct evidence of oxygen evolution from Li1+ x (Ni1/3Mn1/3Co1/3)1? x O2 at high potentials

Li_1+x (Ni_1/3Mn_1/3Co_1/3)_1−x O₂ (NMC) oxides are among the most promising positive electrode materials for future lithium–ion batteries. A voltage “plateau” was observed on the first galvanostatic charging curve of NMC in the extended voltage region positive to 4.5 V vs. Li/Li⁺ for compounds with x > 0 (overlithiated compounds). Differences were observed in the cycling stability of the overlithiated and stoichiometric (x = 0) NMC oxides in this potential region. A differential plot of the charge vs. potential profile in the first cycle revealed that, for the overlithiated compounds, a large irreversible oxidative peak arises positive to 4.5 V vs. Li/Li⁺, while in the same potential region only a small peak due to the electrolyte oxidation is detected for the stoichiometric material. Differential Electrochemical Mass Spectrometry (DEMS) was used to investigate the high voltage region for both compounds and experimental evidence for oxygen evolution was provided for the overlithiated compounds at potentials positive to 4.5 V vs. Li/Li⁺. No oxygen evolution was detected for the stoichiometric compound.     

Caffeic Acid Enhances the Anti-Leukemic Effect of Imatinib on Chronic Myeloid Leukemia Cells and Triggers Apoptosis in Cells Sensitive and Resistant to Imatinib

Among the phenolic acids tested on the K562 cell line, a model of chronic myeloid leukemia (CML), caffeic acid (CA) was biologically active on sensitive and imatinib (IM)-resistant cells at micro-molar concentration, either in terms of reduction of cell proliferation or triggering of apoptosis. The CA treatment provoked mitochondrial membrane depolarization, genomic DNA fragmentation and phosphatidylserine exposure, hallmarks of apoptosis. Cell cycle analysis following the treatment with comparable cytotoxic concentrations of IM or CA showed marked differences in the distribution profiles. The reduction of cell proliferation by CA administration was associated with increased expression of two cell cycle repressor genes, CDKN1A and CHES1, while IM at a cytotoxic concentration increased the CHES1 but not the CDKN1A expression. In addition, CA treatment affected the proliferation and triggered the apoptosis in IM-resistant cells. Taken together, these data suggested that CA induced the anti-proliferative effect and triggered apoptosis of CML cells by a different mechanism than IM. Finally, the combined administration of IM and CA at suboptimal concentrations evidenced a synergy of action in determining the anti-proliferative effect and triggering apoptosis. The ability of CA to potentiate the anti-leukemic effect of IM highlighted the nutraceutical potential of CA in CML.     

Biodegradation of poly(lactic acid)—cassava bagasse composites produced by injection molding

Neat poly (lactic acid) (PLA) and PLA/cassava bagasse (CB) composites were used to produce seedling tubes by extrusion and injection molding. The tubes were buried in simulated soil, and their biodegradation was investigated by weight loss, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). After 180 days, the composites' biodegradation was higher than neat PLA material, and the higher the CB content, the higher the biodegradation, which caused fissures and voids in the material. The biodegradation of PLA/CB composites increased the phosphorus content in the soil after 180 days. Composites of PLA with CB, an abundant agro-industrial residue in Brazil, are promising because they can reduce the environmental impact due to CB's proper destination, and the composites' costs and biodegradation are faster than pure PLA material. Both the faster biodegradation of the tube and the higher P content are advantageous for seedling tubes.     

Antistatic packaging based on PTT/PTT-g-MA/ABS/MWCNT nanocomposites: Effect of the chemical functionalization of MWCNTs

Polymer/carbon nanotube nanocomposites have attracted high interest for a wide spectrum of applications, including antistatic packaging used to protect electronic devices against electrostatic discharge. Polytrimethylene terephthalate (PTT)/maleic-anhydride-grafted PTT (PTT-g-MA)/acrylonitrile butadiene styrene (ABS) blend-based multiwall carbon nanotubes (MWCNTs) nanocomposites were prepared through extrusion. It was conducted chemical functionalization on the MWCNTs by oxidation using nitric acid to introduce functional groups. The effect of the amount (0.5 or 1.0 wt%) and functionalization of MWCNTs on the nanocomposites was investigated. Despite the poor barrier properties of PTT/PTT-g-MA/ABS/MWCNT nanocomposites due to the presence of voids confirmed by scanning electron microscopy (SEM), the nanocomposites with functionalized MWCNT (MWCNTf) showed excellent barrier properties, indicating that the functionalization process improved the interaction between the MWCNTs and the matrix. The addition of MWCNTs into PTT/PTT-g-MA/ABS blend decreased the electrical resistivity by eight orders of magnitude. The use of MWCNTf may still disrupt the electrical network pathway and slightly decreasing the electrical resistivity, but the nanocomposites present the desired properties required for antistatic packaging.