Improved liquid chromatographic method for the analysis of photosynthetic pigments of higher plants

The paper presents an improved reversed-phase LC method for the separation of the pigments from green leaves. A good separation of carotenoids and of their cis- and trans-isomers was achieved, especially for the separation of trans-lutein, zeaxanthin, cis-lutein, which are usually not well separated. No perfect separation of alpha-carotene, beta-carotene and pheophytin a was possible, but conditions for a perfect coelution of pheophytin a with either beta-carotene or alpha-carotene were established. Simultaneous equations allowing the determination of pheophytin a and alpha-carotene or pheophytin a and beta-carotene are also given.     

Six-dimensional quantum dynamics of (v=0,j=0)D2 and of (v=1,j=0)H2 scattering from Cu111

We report six-dimensional quantum dynamics calculations of the dissociative scattering of molecular hydrogen from the copper111 surface. Two potential energy surfaces are investigated and the results are compared with experiment. Our study completes the preliminary work of Somers et al. [Chem. Phys. Lett. 360, 390 (2002)] and focuses on the role of initial vibrational excitation and on isotopic effects. None of the two investigated potential energy surfaces is found satisfactory: the use of neither potential yields reaction and vibrational excitation probabilities and vibrational efficacies that are in close agreement with experiment. In addition to showing the shortcomings of existing potential energy surfaces we point out an inconsistency in the experimental fits for D2.     

Carbon nanostructures grown with electron and ion beam methods

We present a comparative study where carbon nanostructures were prepared by electron and ion beam methods. Thin films of 10×10 μm² area were prepared and analysed by Raman analysis, nanoindentation, energy dispersive X-ray analysis (EDX) and atomic force microscopy (AFM). The material formed is not soft and graphitic, but of intermediate hardness (6–13 GPa) and with Raman spectral features similar to those of hydrogenated amorphous carbon, although it contains a significant Ga content (up to 25 at. %). This study was used to form sharp AFM supertip structures which were used to image sintered ceramic samples and films of aligned carbon nanotubes. Compared to traditional Si tips, this gave an improved rendering of the sample’s aspect ratio although the resolution is limited by the diameter of the C supertips. PACS 81.05.Uw; 81.07.-b; 78.30.-j     

Intrinsic mechanical properties of ultra-thin amorphous carbon layers

In this work, we extracted the film's hardness (H_F) of ultra-thin diamond-like carbon layers by simultaneously taking into account the tip blunting and the substrate effect. As compared to previous approaches, which did not consider tip blunting, this resulted in marked differences (30-100%) for the H_F value of the thinner carbon coatings. We find that the nature of the substrate influences this intrinsic film parameter and hence the growth mechanisms. Moreover, the H_F values generally increase with film thickness. The 10 nm and 50 nm thick hydrogenated amorphous carbon (a-C:H) films deposited onto Si have H_F values of, respectively, ∼26 GPa and ∼31 GPa whereas the 10 nm and 50 nm thick tetrahedral amorphous carbon (t-aC) films deposited onto Si have H_F values of, respectively, ∼29 GPa and ∼38 GPa. Both the a-C:H and t-aC materials also show higher density and refractive index values for the thicker coatings, as measured, respectively by X-ray reflectometry and optical profilometry analysis. However, the Raman analysis of the a-C:H samples show bonding characteristics which are independent of the film thickness. This indicates that in these ultra-thin hydrogenated carbon films, the arrangement of sp² clusters does not relate directly to the hardness of the film.     

Ueber die Wirkung des Magnesiums auf Salzl?sungen

Ohne Zusammenfassung     

Comparative dissociation of peptide polyanions by electron impact and photo-induced electron detachment

We compare product-ion mass spectra produced by electron detachment dissociation (EDD) and electron photodetachment dissociation (EPD) of multi-deprotonated peptides on a Fourier transform and a linear ion trap mass spectrometer, respectively. Both methods, EDD and EPD, involve the electron emission-induced formation of a radical oxidized species from a multi-deprotonated precursor peptide. Product-ion mass spectra display mainly fragment ions resulting from backbone cleavages of C_α-C bond ruptures yielding a and x ions. Fragment ions originating from N-C_α backbone bond cleavages are also observed, in particular by EPD. Although EDD and EPD methods involve the generation of a charge-reduced radical anion intermediate by electron emission, the product ion abundance distributions are drastically different. Both processes seem to be triggered by the location and the recombination of radicals (both neutral and cation radicals). Therefore, EPD product ions are predominantly formed near tryptophan and histidine residues, whereas in EDD the negative charge solvation sites on the backbone seem to be the most favorable for the nearby bond dissociation.     

Synthesis,Crystal Structure and IR Spectra of Complexes of Mn(II) by Indole-2-Carboxylic or Isoquinoline-1-Carboxylic Acids and 1,10-Phenanthroline

Abstract  

Two ternary complexes of manganese(II) indole-2-carboxylate (2-IC⁻) or isoquinolinecarboxylate (IQC⁻) with 1,10-phenanthroline (phen) in methanol or in dimethylacetamide (DMA) were synthesized and studied by X-ray diffraction and IR spectra. [Mn(C₉H₆NO₂)₂(C₁₂H₈N₂)₂]·CH₄O (1) crystallizes in the triclinic space group P-1 with cell parameters of a = 10.548(2) ?, b = 14.168(3) ?, c = 14.580(3) ?, α = 62.35(2)°, β = 69.16(2)°, γ = 78.61(2)°, V = 1802.4(6) ?³ and Z = 2; [Mn(C₁₀H₆NO₂)₂(C₁₂H₈N₂)].C₄H₉NO (2) crystallizes in the monoclinic space group P2₁/a with cell parameters of a = 15.304(5) ?, b = 12.871(5) ?, c = 17.421(5) ?, β = 114.39(1), V = 3125(2) ?³ and Z = 4. In 1, Mn is six-coordinate by two bidentate phen ligands and two 2-IC⁻ ligands and exhibits a very distorted octahedral geometry. This complex is solvated by methanol involved in hydrogen bonding. In 2, Mn atom is surrounded by one bidentate phen ligand and two bidentate IQC⁻ ligands. The complex exhibits a distorted octahedral geometry around the Mn^II atom. The crystal structure is completed by a disordered DMA solvate molecule. The IR spectra of both compounds are slightly different in the range 4000–2400 cm⁻¹ which may be attributed to hydrogen bond lack in 2.