Stereospecific nucleophilic substitution at the C-4α position of 2α-chloro-2'(2',6')-(di)halogenopicropodophyllotoxin derivatives with carboxylic acids mediated by BF3·Et2O was described. Interestingly, this stereoselective products were completely controlled by the reaction time. That is, if the reaction time was prolonged to 24.5-31 h, the resulting compounds were all transformed into the unu...

Our objective was to compare 1.09 M methanolic HCl to 14% BF3 in methanol as catalysts for direct transesterification of fatty acids in freeze-dried forage samples. Samples included blue grama (Bouteloua gracilis), fringed sage (Artemisia frigida), western wheatgrass (Pascopyrum smithii), needle-and-thread (Stipa comata), dalmation toadflax (Linaria dalmatica), needleleaf sedge (Carex eleochari...

Although nanoparticles (NPs) are known to increase foam stability, stabilisation is not observed in all surfactant/NP combinations. The present study evaluates the stability of CO2 foams containing mixtures with attractive or repulsive electrostatic interactions at low pH imposed by presence a high-salinity brine. Three ionic surfactants and two oxide NPs (SiO2 Al2O3) were used combinations sim...

We examined the capacity of SiO2@Cu core-shell nanoparticles to inhibit Escherichia coli and Streptococcus mutaus. Before after addition silicate, copper showed a surface plasmon resonance (SPR) with peak in 620–630 nanometers' region. SiO2@cu nanoparticle manufacturing was further demonstrated have spherical shape, as TEM. The crystal structure SO2 @cu we found matches X-ray diffraction patter...

We present ultrafast spectroscopic investigations of the coherent acoustic vibrations Au/SiO2 and Au/TiO2 core–shell nanoparticles (NPs) upon excitation Au surface plasmon resonance. The oscillations are detected in region interband transitions deep-ultraviolet, where they appear form intensity modulations with no changes spectra. For NPs, oscillation period (typically ∼10 ps) is similar to tha...

Catalytic aerobic oxidation of benzyl alcohol (BnOH) to benzaldehyde (PhCHO) over supported noble metal catalysts has grabbed the attention researchers due critical role PhCHO in numerous industrial syntheses. In present study, a novel catalyst, Pd-P alloy on aminopropyl-functionalized mesoporous silica (NH2-SiO2), was prepared through situ reduction and characterized by BET-BJH analysis, SEM, ...

Nanoparticle-imprinted matrices (NAIMs) were prepared using ammonium-terminated SiO2 nanoparticles (NPs) as templates initially attached to activated glassy carbon. After electrodeposition of a matrix polyplumbagin and polyphenol, the selectivity polymer was tuned towards ligand shell Au analyte NPs by conjugate addition substituted thiols plumbagin moiety within matrix. The reactions followed ...

Litter decomposition is a fundamental process for nutrient cycling but we have a limited understanding of this process in disturbed tropical forests. We studied litter decomposition over a 10-mo period in a seasonally dry Amazon forest in Mato Grosso, Brazil. The study plots (50 ha each) included unburned forest (UF), once-burned (BF1) and forest burned annually for 3 y (BF3). We measured under...

The high carrier mobility of graphene makes it an attractive candidate for future electronic device applications.(1) In SiO2/Si-supported graphene devices, the mobility typically varies from 2000 to ∼2,0000 cm(2) V(-1) s(-1).(2) By removing SiO2,(3,4) much higher mobility (2 × 10(5) cm(2) V(-1) s(-1) in the latter) has been obtained, suggesting the importance of the Coulomb scattering in graphe...

BACKGROUND The aim of our work was to compare two methods, both based on direct transmethylation with different reagents, BF3/MeOH (boron trifluoride in methanol) or HCl/MeOH (hydrochloride acid in methanol), in acid catalysis, without prior extraction, to find the fast, non-expensive but enough precise method for 9 principal fatty acids (lauric, myristic, palmitic, stearic, oleic, linoleic, li...