Effect of gamma irradiation on antiradical activity of goji berry fruits (Lycium barbarum) evaluated by EPR spectroscopy

Antiradical activity of goji berry (Lycium barbarum) was evaluated by means of electron paramagnetic resonance spectroscopy. The goji berry samples were exposed to gamma-irradiation at doses 0.05, 2 and 10 kGy. The characteristic satellite lines from cellulose radicals can prove irradiation treatment. Their intensity increase after alcohol washing and lyophilization. The fading property of satellite lines show that identification of radiation treatment is possible for 50 days. The effect of irradiation on antiradical properties of goji berry extracts was investigated by radical scavenging activity using the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH). The percentages of scavenged DPPH radicals and IC₅₀ of the extracts of goji berry before and after irradiation were calculated. The antioxidant capacity was presented in Trolox Equivalents as well. It was found out that gamma irradiation of goji berry fruits increases its antiradical activity.

     

Structure du reactif d'ivanov et de quelques organometalliques issus des derives phenylacetiques—I : Etude des solutions par rmn

Ivanov reagent add several analogous reagents (phenyl acetique serie) have been studied by NMR. In all the cases, an enolate-structure is revealed; no carbaneniate-species could be detected, even in very solvating solvents.     

Off-center Li ions: solid state rotators described by Mathieu's nonlinear-oscillator equation

Substitutional impurity ions in crystals are known to displace off-center and to perform hindered rotations around the ideal lattice positions. The vibronic theory to describe both the off-center displacements and the hindered rotations by a single angular equation incorporates terms up to 3rd order in the off-center displacement coordinates. When the rotation is confined to a single plane, the corresponding vibronic equation is equivalent to Mathieu's equation. Extending our earlier work, we derive here the dipole-dipole coupling to take into account cooperative phenomena. We also derive the optical absorption band arising from dipolar transitions across “Mexican Hat” surfaces, and we show that hindered rotations gives rise to magnetic moments quantized in rotational bands. Received 18 October 2001 / Received in final form 5 March 2002 Published online 2 October 2002 RID="a" ID="a"e-mail: allxrose@hotmail.com     

Motion Planning of Robot Locomotion

Since the treatment of robot locomotion is quite closed with this one of human locomotion, the present paper treats the problems of modelling, simulation and motion planning of robot locomotion on the base of knowledge of the skeletal system, as well as on the base of multibody system modelling, simulation and control using some ideas from Lie group theory and differential geometry.     

Behavior of Nitroxide Biradicals with Acetylene Bridges in Organic Solvents and Ionic Liquids

Intramolecular electron spin exchange (IESE) in two nitroxide biradicals, R₆–C≡C–C≡C–R₆ (1) and R₆–C≡C–p-C₆H₄–C≡C–R₆ (2), is studied as a function of temperature and solvent properties. The effect of molecular solvents and ionic liquids (ILs, [1-methyl-3-butylimidazolium]⁺[PF₆]^?, bmimPF₆, and [1-methyl-3-octylimidazolium]⁺[BF₄]^?, omimBF₄) on the IESE in magnetically diluted solutions is investigated. Changes in electron paramagnetic resonance spectra are analyzed and the thermodynamic parameters of these changes are calculated. Geometry optimization and D-tensor calculations of biradicals 1 and 2 were carried out on the DFT/UB3LYP/cc-pVdz and DFT/ROPBE/N07D levels of theory. The probable differences in biradical behavior are discussed.     

Behavior of Short Nitroxide Biradical in Room Temperature Ionic Liquids

The intramolecular electron spin exchange in short nitroxide biradical O=S(OR₆)₂ (I), where OR₆ is 1-oxyl-2,2,6,6-tetramethyl-4-oxypiperidine, dissolved in the room temperature ionic liquids (RTILs) 1-octyl-3-methylimidazolium hexafluorophosphate (omimPF₆), 1-octyl-3-methylimidazolium tetrafluoroborate (omimBF₄), 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF₄), and 1-ethyl-3-methylimidazolium tetrafluoroborate (emimBF₄) has been studied by electron paramagnetic resonance (EPR) spectroscopy as a function of temperature. Temperature variations of the isotropic nitrogen hyperfine splitting constant a were measured from EPR spectra. Thermodynamic parameters of the conformational rearrangements were calculated and compared with literature data. These intramolecular movements in rather rigid short-chain biradical I dissolved in four different RTILs are described well by the Debye–Stokes–Einstein law. Unrestricted density-functional-theory calculations of the geometry and electronic structure of the biradical were carried out using the ORCA program package, and showed that the O=S< group is available for the interaction with anions and cations of RTIL. The possible mechanism of such conformational transitions in biradical I in RTIL is discussed.     

Multiresidue determination of pesticides by solid-phase extraction and GC-MS for control of peach production in Bulgaria

A multiresidue analytical method based on acetone extraction and clean-up/pre-concentration on polymeric sorbents was validated for 42 pesticides in peach matrix in order to control safety of fresh production on the Bulgarian market. Matrix-matched calibration was used by addition of pesticides just before SPE. In this way the standards and the samples undergo exactly the same procedure and an improvement of recoveries for the target analytes was observed. The identification and quantification were done by gas chromatographic technique with mass-spectrometric detection (GC-MS). The limits of detection obtained were 0.005?mg?kg^–1 or lower for the most of analytes, and the recovery data were in range 73–109% at three spiked levels 0.01, 0.1 and 0.2?mg?kg^?1. The validated method was used for monitoring of selected pesticides in fresh peach fruits home production. Approximately 30% of the analysed lots (total 33 samples) contained residues mainly of cypermethrin and procymidone, but did not exceed EU MRLs.     

A PETERSON OLEFINATION REACTION USING SILYL-SUBSTITUTED SULFONAMIDE CARBANIONS. SYNTHESIS OF VINYLIC SULFONAMIDES

Abstract

α-Trimethylsilyl-substituted sulfonamides RCH(SiMe₃)SO₂N(CH₃)₂ (3), (R[dbnd]H, CH₃ and C₆H₅) are synthetized in almost quantitative yields. Their lithium derivatives 4 undergo a smooth Peterson olefination reaction with nonenolisable carbonyl compounds to give good to excellent yields of vinylsulfonamides 6. With R[dbnd]H, the reaction is highly E-stereoselective. Moderate stereoselectivity is obtained in the cases of R[dbnd]CH₃ and R[dbnd]C₆H₅.     

ESR and ENDOR investigations of the degenerate electron exchange reactions of various viologens in solution. Solvent dynamical effects

The temperature dependences of the rates of the degenerate electron transfer of various viologens (1,1′-di(hydrocarbyl)-4,4′-bipyridinium salts) are measured in seven different solvents by means of electron spin resonance (ESR) line broadening. Rates vary between 1.7·10⁸ and 1.1·10⁹ M⁻¹s⁻¹ at room temperature and clearly show a solvent dynamical effect, which is inferred from the dependence of the rate constants on the longitudinal relaxation time of the solvent. Activation energies ranging from 5.3 to 24.4 kJ mol⁻¹ are found. For the first time, hyperfine coupling constants are reported for the radical cations of the hydroxyethyl viologen and the amino viologen based on both continuous-wave ESR and electron-nuclear double resonance spectroscopy. Furthermore, the temperature and the solvent dependence of the hyperfine coupling constants of the methyl viologen radical cation are reported.     

Structure du reactif d'ivanov et de quelques organometalliques issus des derives phenylacetiques—II : Stereochimie de la condensation avec la t-butyl-4 cyclohex-anone

Ivanov reagent and some other analogous reagents (phenyl acetique serie) have been condensed with t-Bu-4 cyclohexanone in order to complete investigation of the reactive species. In all the cases, equatorial attack is highly predominant; it let suppose that enolate, detected by NMR, is the reactive species.