Fine structure of the 1s5f and 1s5g levels of He I

The fine structure of the 1s5f and 1s5g levels of He I was measured using microwave spectroscopy. The helium atoms were excited by ion impact, and the eleven allowed 1s5f ^2S+1 F _J –1s5g ^2S′+1 G _J , transitions near ν≈15 GHz were induced and detected by measuring the 1s4d–1s2p or 1s3d–1s2p spectral-line intensities of the impact radiation as a function of the microwave frequency. The measured transition frequencies are in accord with theoretical values and, except for one transition frequency, with earlier experimental data. The existing discrepancy between these earlier data and theory could be solved.     

Interaction of 3,5-di-tert-butyl-o-benzoquinone with secondary amines—a pathway to new sterically hindered N,N-disubstituted o-aminophenols

The interaction of 3,5-di-tert-butyl-o-benzoquinone with secondary amines has been studied. The synthetic procedure was developed in order to synthesize a series of new N,N-disubstituted o-aminophenols. The interaction of 3,5-di-tert-butyl-o-benzoquinone with dimethylamine leads to 2-(N,N-dimethylamino)-4,6-di-tert-butyl-phenol, which is oxidized in the reaction medium by the parent 3,5-di-tert-butyl-o-benzoquinone forming spirocompound 4,5′,6,7′-tetra-tert-butyl-3′-methyl-3′H-spiro[1,3-benzodioxol-2,2′-[1,3]benzoxazole].     

An improved model of the fringing fields of a quadrupole mass filter

The fringing field region of a quadrupole mass filter is modelled using an iterative finite difference technique to solve Laplace's equation for the electrostatic potential. The results are used to formulate an expression f(z) such that the electrostatic potential of the fringing field, F(x, y, z, t) may be written in the form F(x, y, z, t) = f(z) φ(x, y, t), where φ(x, y, t) is the hyperbolic field of the quadrupole. The function f(z) is expressed in the form f(z) = 1 - exp {- az - bz²}), where a and b are constants and z is in units of r_O, where 2r_O is the spacing of the quadrupole rods. The effect of the distance from the quandrupole rods to the end plate of the quadrupole mass filter, d on f(z) is investigated and the results presented show that for d < 0.125 r_O the function f(z) does not alter significantly.     

Hyperfine structure in the configurations4f 4 6s 2 and4f 4 5d 6s of Nd I

The high resolution laser-atomic-beam technique was used to investigate the hyperfine structure in Nd I 4f ⁴6s ^{2 5} I,⁵ F,⁵ S and 4f ⁴5d6s ⁷ L,⁷ K,⁷ I,⁷ H. The metastable states were populated by an arc discharge burning in the atomic beam. The measured hyperfine constantsA andB of the levels of 4f ⁴6s ² and 4f ⁴5d6s allow a parametric analysis to be performed using the effective tensor operator formalism. The experimental radial integrals of the 4f and 5d electrons fit with those of the other lanthanides. The 4f radial integrals are in agreement with values of optimized Hartree-Fock-Slater calculations. The spectroscopic quadrupole moments of¹⁴³Nd and¹⁴⁵Nd are deduced from the 4f parameters:Q _I =?0.610(21) b and ?0.314(12) b, respectively. TheQ _I resulting from the 5d parameter are in satisfactory agreement with these values. The hyperfine anomaly due to thes electron in 4f ⁴5d 6s amounts to about 1%.     

Stability of Rare-Earth Oxychloride Phases: Bond Valence Study

The crystal structures of the tetragonal rare earth (RE) oxychlorides, REOCl (RE=La-Nd, Sm-Ho, and Y) were studied by X-ray powder diffraction measurements, Rietveld analyses, and bond valence calculations. The tetragonal structure (space group P4/nmm, No. 129, Z=2) is stable for all but Er-Lu oxychlorides, which possess a hexagonal structure. The tetragonal structure consists of alternating layers of (REO)_nⁿ⁺ complex cations and Xⁿ⁻ anions, where the rare earth is coordinated to four oxygens and four plus one chlorines in a monocapped tetragonal antiprism arrangement. The Rietveld analyses yielded a coherent series of structural parameters. Preferred orientation and microabsorption effects were found significant. The evolution of interatomic distances and bond angles indicated that the reason for the preferred structure changing from tetragonal to hexagonal is the strain in the chlorine layer. The bond valence parameter B for the RE-O bonds had to be recalculated due to the covalent nature of the (REO)_nⁿ⁺ unit. The results obtained with the new parameter confirmed the strains in the chlorine layer to be the cause for the phase transition.     

The crystal and molecular structure of 10,10-dimethyl-10-germa-9-thio-9,10-dihydroanthracene

The X-ray analysis of 10,10-dimethyl-10-germa-9-thio-9,10-dihydroantracene has been carried out. The crystals are orthorhombic: a 11.130(3), b 7.556(2), c 30.795(5) »; Z = 4; space group Pbca. The structure was solved by a combination of Patterson and Fourier methods and refined to R = 0.047 (R_w = 0.050, w = 1/a²(F₀)). The molecule is not planar and the dihedral angle formed by the two benzene rings is 143.6°. The central ring has the boat conformation. The ¹³C NMR chemical shifts associated with benzene carbon atoms correlate well with bond angles obtained by X-ray methods.     

Effect of blending way on β-crystallization tendency of compatibilized β-nucleated isotactic polypropylene/poly(ethylene terephthalate) blends

The main purpose of this study is to investigate the β-crystallization tendency in the β-nucleated iPP blends. The β-nucleated iPP/compatibilizers blends, β-nucleated iPP/PET blends and its compatibilized versions with four kinds of compatibilizers (PP-g-MA, PP-g-GMA, POE-g-MA, and EVA-g-MA) were prepared by different blending ways. The effect of compatibilizers and blending ways on the non-isothermal crystallization and melting characteristics and the β-crystallization tendency of β-nucleated iPP blends were studied by differential scanning calorimetry. The relative content of the β-phase were characterised by the k _β values determined on the basis of the wide angle X-ray diffractogram. The results indicated that the β-crystallization tendency of β-nucleated iPP blends depends on the kinds of compatibilizer. Addition of PP-g-MA significantly reduced the β-crystallization tendency of β-nucleated iPP, while PP-g-GMA, POE-g-MA, and EVA-g-MA have little effect on it. In the compatibilized β-nucleated iPP/PET blends, the blending ways, which controlled the dispersion of β-nucleating agent, influences the β-crystallization tendency intensively. The high β-crystallization tendency and β-crystal content were obtained for compatibilized β-nucleated iPP/PET blends prepared firstly at high temperature and β-nucleating agent added into blends at low temperature; however, the type of compatibilizers has little effect on β-crystallization tendency and melting behavior of blends.     

Fine structure and transition probabilities of the 2p 5 nl bound excited states of Ne atom

We present a semi-empirical calculational procedure for thep ⁵ nl bound excited states of rare gas atoms based on the use of an LS-dependent orbital for an excitednl electron outside a frozen Hartree-Fockp ⁵ core. The spin-orbit interaction is accounted for approximately using a localized Hartree potential. The contribution from the long-range core polarization is estimated by using a parametrized potential. A model potential is also introduced to represent partially the short-range multi-electron interactions for thep ⁵ np levels. The energy levels are calculated by diagonalizing the Hamiltonian matrix following anLS →jl transformation. The calculated fine structure of the Nep ⁵ ns,p ⁵ np,p ⁵ nd, andp ⁵ nf ¦ (jl)KJ〉 levels are in close agreement with the observed level splittings. The transition probabilities are also in agreement with earlier theoretical and experimental results.     

Factors affecting the ultramicro-determination of tryptophan,kynurenine and their derivatives

The factors affecting the ultramicrodetermination of tryptophan and kynurenine were investigated by paper electrophoresis, paper chromatography and spectrophotometry. The electrolyte used in electrophoresis influences the mobility, the separation and the ultraviolet spectra of tryptophan and kynurenine. The pre-treatment of filter paper for chromatography did not influence the R_F of tryptophan and kynurenine, but interfered with their quantitative determination. The effect of ultraviolet irradiation of d-, l-, and dl-tryptophan as well as d-, l-, and dl-kynurenine was studied.     

Stereoselective synthesis of (2S,3S,7S)-3,7-dimethylpentadecan-2-ol and its propionate,the sex pheromones of pine sawflies

The stereoselective synthesis of (2S,3S,7S)-3,7-dimethylpentadecan-2-ol (diprionol) and its propionate, the sex pheromones of pine sawflies (Neodiprion sp. and other), in high enantiomeric purity was achieved from (1R,3S)-2,2-dichloro-3-methylcyclopropanecarboxylic acid. The carbon skeleton of diprionol was formed via copper-catalyzed cross-coupling reactions and diastereoselective methylation of the intermediate chiral α-methylbranched aldehyde with MeTi(Oi-Pr)₃ in the presence of [(R,R)-TADDOL]Ti(Oi-Pr)₂. The latter transformation leads to a syn-adduct with high stereoselectivity, which depends on the presence and configuration of the α-stereogenic center in the aldehyde. The diastereomeric purity of (2S,3S,7S)-diprionol can be substantially increased via crystallization of its 3,5-dinitrobenzoate.     

Green's function calculation of ionization energies of Ca (Z=20), Kr (Z=36), Sr (Z=38) and Yb (Z=70)

The Ca 3s, Kr 4s, Sr 4s and Yb 5s atomic ionization spectra are calculated using the one-particle Green's function method within the framework of Random phase approximation with exchange. Pronounced final ionic correlation effects are found for these levels. The relative intensity of the main ionic state is reduced considerably byns ^?1?np ^?2 nd super Coster Kronig process. The ionization energy of the main ionic state is shifted as much as ～4 eV from the relativistic Hartree-Fock ΔSCF ionization energy byns ^?1?np ^?2 nd super Coster-Kronig process. The existence of strongnp ^?2 nd ² S satellite is predicted for these levels.     

Preparation of fluorinated esters of abietic acid

The reaction of abietic acid chloride with sodium salts of 1H,1H-dihydrotrifluoroethanol, 1H,1H,3H-trihydrotetrafluoropropanol, 1H,1H,5H-trihydrooctafluoropentanol, and pentafluorophenol was studied. The main reaction products are the corresponding fluorinated alkyl (aryl) abietates.     

Synthese des substances de groupe sanguin—IX: Une synthese du 2-o-(α-l-fucopyranosyl)-3-o-(α-d-galactopyranosyl)-d-galactose,le determinant antigenique du groupe sanguin b

The trisaccharide 2-O-(α-L-fucopyranosyl)-3-O-(α-D-galactopyranosyl)-D-galactose has been synthesised stereospecifically using the imidate procedure. Allyl 3-O-benzoyl-4,6-O-benzylidene-β-D-galactopyranoside was first α-L-fucosylated by 1-O-(N-methyl)-acetimidyl-2,3,4-tri-O-benzyl-β-L-fucopyranose then, after O-debenzoylation, α-D-galactosylated by 1-O-(N-methyl)-acetimidyl 2,3,4,6-tetra-O-benzyl-β-D-galactopyranose. The resulting tri-saccharide has also been obtained from allyl 2-O-benzoyl-4,6-O-benzylidene-β-D-galactopyranoside after α-D-galactosylation, O-debenzoylation and α-L-fucosylation. The glycosylations were performed at room temperature in nitromethane in the presence of p-toluenesulfonic acid. Deallylation followed by catalytic hydrogenolysis gave the B blood-group antigenic determinant. The allyl group was also selectively transformed into hydroxyethyl group.     

Concentration dependence of critical exponents for gelation in gellan gum aqueous solutions upon cooling

The sol-gel transition in aqueous gellan gum solutions induced upon cooling was investigated by rheology measurements. The gelation temperature was determined from the crossover point of storage and loss moduli, i.e., G′ = G′′ (T_c) and from the Winter’s criterion (T_gel), respectively, which increased with gellan concentration. T_gel was higher than T_c and the difference became larger as the gellan concentration got higher. The relaxation critical exponent n was estimated with the Winter’s method and the self-similarity was observed from the critical gel. The scaling for the zero-shear viscosity η₀ before the gel point and the equilibrium modulus G_e after the gel point was established against the relative distance ε from the gel point over the gellan concentration C_g of 1.0-2.5 wt%, giving the critical exponents k and z. The critical exponent n calculated from k and z agrees well with n from the Winter’s criterion. However, no universal n was found for the gelation in aqueous gellan gum solutions, indicating that this gelation should be classified into the cross-linking category for the physical gelation. The critical exponent n decreased with increasing C_g for the gellan gum solution. The fractal dimension d_f calculated from n with the screened hydrodynamic interaction and the excluded volume effect suggested a denser structure in the critical gel with higher C_g.     

Structural,magnetic and transport properties of S doping in Sr2FeMoO6 compound

The polycrystalline Sr₂FeMoO_6-xS_x (0.0 ≤ x ≤ 0.4) series were synthesized. The structure of Sr₂FeMoO_6-xS_x is assigned to tetragonal system with space group I4/mmm. The cell volume decreases with x from 0.0 to 0.3, then, increases with x from 0.3 to 0.4. S doping leads the oxygen/sulfur at 4e and 8h positions to movement away from Fe and to displacement toward Mo, respectively. The M_S at room temperature increases with degree of order of Fe and Mo ions. The electrical resistivity for studied samples exhibits a semiconductor-like behavior. The resistivity decreases with S doping. The electrical transport behavior is mainly dominated by electron-electron interactions except x = 0.4 in 0.0 magnetic field.     

Synthesis of oligomers including eight P-chiral centers and the construction of the 12-phosphacrown-4 skeleton

The stepwise oxidative coupling reaction from (S,S)-1 gave optically active oligomers, (S,R,R,S)-2 and (S,R,S,R,R,S,R,S)-3, having four and eight chiral phosphorus atoms, respectively. The behaviors of these oligomers in the solid state and in solution were investigated in detail. The first construction of a 12-phosphacrown-4 skeleton was also reported.     

Bound state energies for the exponential cosine screened Coulomb potential

The energy eigenvalues of bound states of an electron in the general exponential cosine screened Coulomb potential are obtained using the shifted 1/N expansion method. The energies for the states from 1s to 8k are calculated from six to eight significant figures. The energy eigenvalues for the 1s, 2s – 2p, 3s – 3d, and 4s – 4f states are also presented as a function of the screening parameter λ. Results are compared with the ones obtained by other workers. The agreement reduces roughly for large λ. It is also observed that the convergence of the expansion series increases remarkably asl increases.     

Exposure to Anacardiaceae Volatile Oils and Their Constituents Induces Lipid Peroxidation within Food-Borne Bacteria Cells

The chemical composition of the volatile oils from five Anacardiaceae species and their activities against Gram positive and negative bacteria were assessed. The peroxidative damage within bacterial cell membranes was determined through the breakdown product malondialdehyde (MDA). The major constituents in Anacardium humile leaves oil were (E)-caryophyllene (31.0%) and α-pinene (22.0%), and in Anacardium occidentale oil they were (E)-caryophyllene (15.4%) and germacrene-D (11.5%). Volatile oil from Astronium fraxinifolium leaves were dominated by (E)-β-ocimene (44.1%) and α-terpinolene (15.2%), whilst the oil from Myracrodruon urundeuva contained an abundance of δ-3-carene (78.8%). However, Schinus terebinthifolius leaves oil collected in March and July presented different chemical compositions. The oils from all species, except the one from A. occidentale, exhibited varying levels of antibacterial activity against Staphylococcus aureus, Bacillus cereus and Escherichia coli. Oil extracted in July from S. terebinthifolius was more active against all bacterial strains than the corresponding oil extracted in March. The high antibacterial activity of the M. urundeuva oil could be ascribed to its high δ-3-carene content. The amounts of MDA generated within bacterial cells indicate that the volatile oils induce lipid peroxidation. The results suggest that one putative mechanism of antibacterial action of these volatile oils is pro-oxidant damage within bacterial cell membrane explaining in part their preservative properties.     

Kinetic model of the evaporation process of benzylbutyl phthalate from plasticized poly(vinyl chloride)

The kinetic model of the physical process of evaporation of plasticizer from plasticized PVC foils was developed from the results of isothermal thermogravimetric investigation of evaporation of benzyl-butyl phthalate in the temperature range 120-150 °C under nitrogen flow. The kinetic parameters were estimated by integral method of analysis. Mathematical modeling of the kinetic of plasticizers evaporation was performed on the basis of function c=f(T,t) and kinetic equation of evaporation −dc/dt=f(T,c₀,c(t)). The developed mathematical model was described by the general kinetic equation . The differential quotients δ(−dc/dt)/δT=f(T,c₀,c(t))=f(T,c₀,t) and δ(−dc/dt)/δc₀=f(T,c(t))=f(T,c₀,t) were performed, and mathematical definition of the changes of the evaporation rate constant with the change of temperature and the change of the initial plasticized concentration were discussed.     

Precursors to oak lactone. Part 2: Synthesis, separation and cleavage of several β-d-glucopyranosides of 3-methyl-4-hydroxyoctanoic acid

The β-d-glucopyranosides of all four stereoisomers of 3-methyl-4-hydroxyoctanoic acid have been prepared. The (3S,4S) and (3R,4R) species were prepared from cis-5-n-butyl-4-methyl-4,5-dihydro-2(3H)-furanone (cis-oak lactone) by a process involving ring-opening with base and protection of the carboxyl function as its benzyl ester. The glucose unit was introduced by a modified Koenigs-Knorr procedure. A different strategy was necessary for synthesis of the (3S,4R) and (3R,4S) compounds. This was based on the reductive ring-opening of trans-oak lactone and subsequent protection of the primary alcohol as its t-butyldiphenylsilyl ether. Separation of the individual glucosides was effected by preparative thin layer chromatography. Those corresponding to the nature-identical isomers of oak lactone have been shown to produce oak lactone under both acidic hydrolysis and pyrolysis conditions. The galloyl-β-d-glucoside of the cis-species, obtained as a natural isolate from the wood of Platycarya strobilacea, was also found to produce cis-oak lactone upon both acid hydrolysis and pyrolysis. Both the nature-identical (4S,5S) cis-oak lactone and its non-natural (4R,5R) enantiomer have been prepared from their corresponding glycosides and their aroma thresholds in white wine were determined to be 23 and 82 μg/L (ppb) respectively. The aroma threshold of the nature-identical isomer in a red wine was 46 μg/L.