Antioxidant secondary metabolites from Geranium lasiopus Boiss. & Heldr

Chromatographic studies on the EtOAc soluble portion of the MeOH extract of Geranium lasiopus led to the isolation of eight flavonoids (kaempferol (1), quercetin (2), quercetin 3-O-β-glucopyranoside (3), quercetin 3-O-β-galactopyranoside (4), kaempferol 3-O-α-rhamnopyranosyl-(1?→?6)-β-glucopyranoside (5), quercetin 3-O-α-rhamnopyranosyl-(1?→?6)-β-glucopyranoside (6), kaempferol 3-O-α-rhamnopyranosyl-(1?→?2)-β-glucopyranoside (7) and quercetin 3-O-α-rhamnopyranosyl-(1?→?2)-β-glucopyranoside (8)), two simple phenolic compounds (gallic acid (9) and its methyl ester (10)) and a hydrolysable tannin (pusilagin (11)). The structures of the compounds were elucidated by 1- and 2-dimensional NMR techniques ((1)H, (13)C, COSY, HMBC, HMQC) and ESI-TOF-MS spectrometry. Inhibitory effects on H(2)O(2)-induced lipid peroxidation in human red blood cells of the different extracts of G. lasiopus, as well as isolated compounds, were investigated. All tested compounds showed comparable or higher activity than that of ascorbic acid and trolox.     

An Error in Variables Method for Determining the Implicit Penultimate Copolymerization Ratios by On‐Line Monitoring of Reactions

Summary: In copolymerization systems with implicit penultimate effect, there are two radical reactivity ratios, s_a and s_b, which influence the reaction kinetics in addition to the monomer reactivity ratios, r_a and r_b, which govern the copolymer composition. Here, an error in variables method has been developed to determine s_a and s_b. It is based on continuous on‐line monitoring of the polymerization process, where monomer and polymer concentrations are measured through the monitoring of two independent properties of the system. The ratios and the corresponding χ² values were found by taking into account errors emanating from measurements and from calibration of the instruments. It is shown that the kinetic data allows both ratios to be found if both monomer reactivity ratios are less than one. If the system is near ideality (r_ar_b ≅ 1) or if both reactivities are greater than one, only an average radical reactivity ratio, , can be reliably determined.

The 2σ confidence contours for the 3 individual experiments. The reactivity ratios are r_a = 0.5, r_b = 0.2, s_a = 0.3, s_b = 0.4. For clarity the contours are plotted as functions of 1/s_a and 1/s_b.     

Kinetic role of t-amines in the ligand inhibited osmium tetraoxide catalyzed trimethylamine-N-oxide dihydroxylation of alkenes

Kinetic studies on the t-amine inhibited catalytic OsO₄ dihydroxylation of cyclooctene, octene, styrene and 4-methyl-, 4-methoxy-, 4-chloro-, 4-(chloromethyl), 4-(trifluoromethyl) and 3-chloro-derivatives of styrene with Me₃NO in t-BuOH have been carried out at 50 °C. The reactions follow identical kinetics: first order in total osmium species, first order in Me₃NO and zero order in alkene. All t-amines have been found to retard the catalysis and the reaction order in t-amine changes from inverse first order to zero. The involvement of dioxomonoglycolataosmium(VI) esters and their monoamine adducts in the rate-determining oxidation step was established by the linear plots of 1/k ₂ versus. 1/[L] where k ₂ is the decrease in second order rate constant in the presence of [L] concentration of t-amine ligand. Beyond a definite concentration of t-amine, the rate reaches a minimum and remains constant. Activation parameters were evaluated for catalytic OsO₄ dihydroxylation of 4-(chloromethyl)styrene at different t-amine concentrations. The values of H and S are consistent with the proposed mechanism.     

Leaving group effect in the sulfonyl transfer reactions of aryl benzenesulfonates with Grignard reagents

The C–S coupling reactions of aryl benzenesulfonates with phenylmagnesium bromide in THF:toluene (7:10) at 90 °C have been studied. A Hammett-type kinetic study of the leaving group effect of aryloxy groups provides a conclusive support for a two step addition-elimination mechanism in which C–S bond formation is rate determining step.     

Binding of a neutral guest to cucurbiturils: photophysics,thermodynamics and molecular modelling

Steady-state and time-resolved fluorescence techniques were used to study the thermodynamics of binding of a neutral polarity-sensitive guest, the methyl 2-naphthalenecarboxylate (2MN), with three cucurbiturils (CBn; n = 6, 7 and 8) in water. Association constants (K) were obtained from nonlinear regression analysis of the fluorescence intensity against [CB] in the 5–45°C range. 2MN complexed with CB7 exhibited a 1:1 stoichiometry (K ≈ 10³ M^? 1 at 25°C); however, it hardly did with CB6 (K < 10 M^? 1) and it did not with the larger CB8 macrocyclic ring. The (1:1) 2MN:CB7 complexation process was accompanied by a small unfavourable enthalpy change and was, therefore, entropically governed. Molecular mechanics and molecular dynamics calculations in the presence of water were also used to study the geometry of the complexes formed and the driving forces responsible for their formation. The results were compared with those previously obtained for the complexation of the same guest, 2MN, with natural α-, β- and γ-cyclodextrins.     

X‐ray Raman spectroscopy of lithium‐ion battery electrolyte solutions in a flow cell

The effects of varying LiPF₆ salt concentration and the presence of lithium bis(oxalate)borate additive on the electronic structure of commonly used lithium‐ion battery electrolyte solvents (ethylene carbonate–dimethyl carbonate and propylene carbonate) have been investigated. X‐ray Raman scattering spectroscopy (a non‐resonant inelastic X‐ray scattering method) was utilized together with a closed‐circle flow cell. Carbon and oxygen K‐edges provide characteristic information on the electronic structure of the electrolyte solutions, which are sensitive to local chemistry. Higher Li⁺ ion concentration in the solvent manifests itself as a blue‐shift of both the π* feature in the carbon edge and the carbonyl π* feature in the oxygen edge. While these oxygen K‐edge results agree with previous soft X‐ray absorption studies on LiBF₄ salt concentration in propylene carbonate, carbon K‐edge spectra reveal a shift in energy, which can be explained with differing ionic conductivities of the electrolyte solutions.     

Screening of Acrylamide of Par-Fried Frozen French Fries Using Portable FT-IR Spectroscopy

Current assays for acrylamide screening rely heavily on LC-MS/MS or GC-MS, techniques that are not suitable to support point of manufacturing verification because it can take several weeks to receive results from a laboratory. A portable sensor that can detect acrylamide levels in real-time would enable in-house testing to safeguard both the safety of the consumer and the economic security of the agricultural supplier. Our objective was to develop a rapid, accurate, and real-time screening technique to detect the acrylamide content in par-fried frozen French fries based on a portable infrared device. Par-fried French fries (n = 70) were manufactured at times ranging from 1 to 5.5 min at 180 °C to yield a wide range of acrylamide levels. Spectra of samples were collected using a portable FT-IR device operating from 4000 to 700 cm⁻¹. Acrylamide was extracted using QuEChERS and quantified using uHPLC-MS/MS. Predictive algorithms were generated using partial least squares regression (PLSR). Acrylamide levels in French fries ranged from 52.0 to 812.8 µg/kg. The best performance of the prediction algorithms required transformation of the acrylamide levels using a logarithm function with models giving a coefficient of correlation (Rcv) of 0.93 and RPD as 3.8, which means the mid-IR model can be used for process control applications. Our data corroborate the potential of portable infrared devices for acrylamide screening of high-risk foods.     

On reduction of exhausters via a support function representation

Journal of Global Optimization - Exhausters are families of compact, convex sets which provide minmax or maxmin representations of positively homogeneous functions and they are efficient tools for...     

Synthesis,Characterization, and AC Conductivity of Polyaniline/Selenium Composites

This study reports structural and thermal properties and temperature-dependent alternating current (AC) conductivity of polyaniline/selenium (PANI/Se) composites in emeraldine salt form prepared by a chemical polymerization method. Fourier transform infrared spectroscopy showed that the doping process significantly affected the N-H bond in PANI chain. The free energy change, which was calculated from the Langmuir adsorption isotherm, showed that Se was electrostatically adsorbed on PANI molecules. From the scanning electron microscopy images it was determined that morphological changes caused by the doping process on PANI surface could affect conductivity. Thermal analysis, which was performed with differential scanning calorimetry, showed that the addition of Se increased the degradation temperature of PANI. Depending on the doping level, significant increase was observed in the AC conductivity of PANI, approximately 11, 13, and 17 times for 300, 350, and 400 K temperatures respectively.     

Analytic network process in supplier selection: A case study in an electronic firm

Supplier selection, which is the first step of the activities in the product realization process starting from the purchasing of material till to the end of delivering the products, is evaluated as a critical factor for the companies desiring to be successful in nowadays competition conditions. With the scope of this paper, supplier selection was considered as a multi criteria decision problem. A model aiming the usage of analytic network process (ANP) in supplier selection is developed owning to the evaluation of the relations between supplier selection criterias in a feedback systematic. The proposed model is implemented in a company of electronic.