Analysis of the essential oil composition of eight Anthemis species from Greece

The volatile composition of eight Anthemis species has been studied. The essential oils were obtained by hydrodistillation in a modified Clevenger-type apparatus, and their analyses were performed by GC and GC-MS. Identification of the substances was made by comparison of mass spectra and retention indices with literature records. A total of 284 different compounds were identified and significant qualitative and quantitative differences and similarities were observed among the samples. The main constituents of the investigated populations of each taxon have been revealed as follows: A. altissima: (-)-linalool, trans-caryophyllene, cis-chrysanthenyl acetate; A. auriculata: spathulenol, trans-caryophyllene, beta-eudesmol; A. chia: cis-chrysanthenyl acetate, trans-caryophyllene, germacrene-d; A. cotula: germacrene-d, spathulenol A. tinctoria: spathulenol, (-)-caryophyllene oxide, T-cadinol; A. melanolepis: p-cymene, chrysanthenone, trans-verbenol, (-)-caryophyllene oxide; A. tomentosa: (-)-linalool, 1,8-cineole; A. werneri subsp. werneri: nopol, terpineol-4, trans-caryophyllene. Sesquiterpene hydrocarbons were shown to be the main group of constituents of all taxa.     

Distance distributions of short polypeptides recovered by fluorescence resonance energy transfer in the 10 A domain

Fluorescence resonance energy transfer (FRET) between tryptophan (Trp) as donor and 2,3-diazabicyclo[2.2.2]oct-2-ene (Dbo) as acceptor was studied by steady-state and time-resolved fluorescence spectroscopy. The unique feature of this FRET pair is its exceptionally short F?rster radius (10 A), which allows one to recover distance distributions in very short structureless peptides. The technique was applied to Trp-(GlySer)n-Dbo-NH2 peptides with n = 0-10, for which the average probe/quencher distance ranged between 8.7 and 13.7 A experimentally (in propylene glycol, analysis according to wormlike chain model) and 8.6-10.2 A theoretically (for n = 0-6, GROMOS96 molecular dynamics simulations). The larger FRET efficiency in steady-state compared to time-resolved fluorescence experiments was attributed to a static quenching component, suggesting that a small but significant part (ca. 10%) of the conformations are already in van der Waals contact when excitation occurs.     

High-quality alloyed CdSxSe1-x whiskers as waveguides with tunable stimulated emission

High-quality ultra-long alloyed CdS(x)Se(1)(-)(x) (0 < or = x < or = 1) whiskers were obtained by a simple thermal evaporation route. The near band-edge emission in these whiskers can be effectively guided at the sub-millimeter scale under continuous-wave laser excitation. As good optical waveguide cavities, the whiskers exhibit stimulated emissions under pulsed light excitation at room temperature for all compositions 0 < or = x < or = 1. The spectral positions of the sharp emission lines of the whiskers were tuned by their compositions, covering the spectral range from green to red.     

Supramolecular control of oligothienylenevinylene-fullerene interactions: evidence for a ground-state EDA complex

Complementary hydrogen-bonding interactions between a barbituric acid-substituted fullerene derivative (1) and corresponding receptor (2) bearing thienylenevinylene units are used to assemble a 1:1 supramolecular complex (K = 5500 M(-1)). Due to the close proximity of the redox-active moieties within the assembly, strong ground-state electron-donor-acceptor interactions are observed. Photoinduced electron transfer from electron-rich thienylenevinylene subunits to the fullerene is very fast (k(et) = 5.5 x 10(12) s(-1)), as determined by fs-time-resolved transient absorption spectroscopy. [reaction: see text]     

A tetra-nuclear copper(II) complex stabilizes an extended structure of a water nonamer: Synthesis and characterization of [Cu4(C54H46N4O14)(OH)2] · 10H2O

A tetra-nuclear copper(II) complex [Cu₄(C₅₄H₄₆N₄O₁₄)(OH)₂] · 10H₂O (1) has been synthesized starting from l-tyrosine, NaOH, 2,6-diformyl-4-methylphenol (dfp) and CuSO₄ · 5H₂O. Compound 1 crystallizes from an ethanol–water mixture in triclinic space group. In the crystal of 1, two binuclear copper units, related by a center of symmetry, are bridged by two hydroxo bridges and results in the formation of a tetra-nuclear {Cu₄} structure. Five lattice water molecules, located in the asymmetric unit, interact among themselves and form an unusual form of a water nonamer. In the crystal, the water nonamer is again hydrogen bonded to the next nonamer forming a chainlike polymer. Each {Cu₄} complex unit attaches four such water nonamer chains. Variable temperature magnetic data fit to the Bleaney–Bower’s equation with a Curie type of impurity of S = 0.5. The best fit of the magnetic data to this equation yielded 2J = −217, g = 2.019 and a TIP value of 60 × 10⁻⁶ cm³ mol⁻¹.     

分子角动量定向布居的制备探测和它的碰撞弛豫

利用受激Ｒａｍａｎ泵浦,使线性分子Ｃ２Ｈ２选择性地制备振动态角动量定向布居参数Ａσ（１）达到０．７～０．８。并测定了角动量定向布居碰撞诱导的弛豫速率常数,采用园偏振的紫外激光诱导荧光方法,可表征分子角动量定向布居的制备和它的碰撞弛豫过程。     

分子角动量定向布居的制备探测和它的碰撞弛豫

利用受激Raman泵浦,使线性分子C2H2选择性地制备振动态角动量定向布居参数A0(1)达到0.7～0.8。并测定了角动量定向布居碰撞诱导的弛豫速率常数。采用园偏振的紫外激光诱导荧光方法,可表征分子角动量定向布居的制备和它的碰撞弛豫过程。     

Minimal Cuntz-Krieger dilations and representations of Cuntz-Krieger algebras

Given a contractive tuple of Hilbert space operators satisfying certainA-relations we show that there exists a unique minimal dilation to generators of Cuntz-Krieger algebras or its extension by compact operators. This Cuntz-Krieger dilation can be obtained from the classical minimal isometric dilation as a certain maximalA-relation piece. We define a maximal piece more generally for a finite set of polynomials inn noncommuting variables. We classify all representations of Cuntz-Krieger algebrasO _A obtained from dilations of commuting tuples satisfyingA-relations. The universal properties of the minimal Cuntz-Krieger dilation and the WOT-closed algebra generated by it is studied in terms of invariant subspaces.