Crystal and molecular structure of 1-(3,5-dimethyl-2-furyl)-3-(p-tolyl) -prop-2-en-1-one

The structure of 1-(3,5-dimethyl-2-furyl)-3-(p-tolyl)-prop-2-en-1-one, C₁₆H₁₆O₂ is determined by single-crystal x-ray diffractometry. Crystals are triclinic, , a=7.381(7), b=8.871(5), c=10.745(13) Å, =93.53(7), =102.25(8),=95.43(7)°, V=682(1) ų, Z=2, d_calc=1.170 g cm^–3, (Cu K)=1.54178 Å,=5.697 cm^–1, M=270.30, F(000)=256, R=0.077 for 1601 unique observed reflections. The trans-geometry of the C=C double bond, thes-cis-geometry of the C=C-C=O moiety, and thes-trans arrangement of the carbonyl and furane oxygen atoms are proved.     

Sequential Cu-Catalyzed Four- and Five-Component Syntheses of Luminescent 3-Triazolylquinoxalines

3-Triazolylquinoxalines can be readily synthesized by applying two complementary synthetic protocols starting from heterocyclic π nucleophiles or (hetero)aryl glyoxylic acids in a consecutive four- or five-component reaction. Conceptually, the sequential use of a single cuprous salt for alkynylation and Cu-catalyzed alkyne-azide cycloaddition (CuAAC) in a one-pot fashion sets the stage for activation-alkynylation-cyclocondensation-CuAAC or glyoxylation-alkynylation-cyclocondensation-CuAAC sequences in good yields. The diversity-oriented generation of differently substituted 3-triazolylquinoxalines is an excellent entry to tunable emission solvatorchromic fluorophores with triazole ligation. The electronic structure, corroborated by DFT and TD-DFT calculations, rationalizes the charge transfer character of relevant absorptions and large Stokes shifts as well as the electronic innocence of the triazole substituents.     

Bicovariant differential calculus on quantum groups and wave mechanics

The bicovariant differential calculus on quantum groups being defined by Woronowicz and later worked out explicitly by Carow-Watamura et at. and Juro for the real quantum groupsSU _q (N) andSO _q (N) through a systematic construction of the bicovariant bimodules of these quantum groups is reviewed forSU _q (2) andSO _q (N). The resulting vector fields build representations of the quantized universal enveloping algebras acting as covariant differential operators on the quantum groups and their associated quantum spaces. As an application a free particle stationary wave equation on quantum space is formulated and solved in terms of a complete set of energy eigenfunctions.Presented at the Colloquium on the Quantum Groups, Prague, 18–20 June 1992.     

Broad multiwavelength source with 50 GHz channel spacing for wavelength division multiplexing applications in the telecom C band

We present a multiwavelength source with a spectral width of 42 nm at -20 dB. The frequency comb is generated by spectrally broadening the output of an amplified 50 GHz Er:Yb:glass laser with a highly nonlinear photonic crystal fiber. After spectral flattening the comb covers 37 channels with 5.4 mW average power per channel, and locking only one central wavelength channel to the International Telecommunication Union grid results in a maximum frequency error of 0.24% for all channels.     

Online signal extraction by robust linear regression

Summary  In intensive care, time series of vital parameters have to be analysed online, i.e. without any time delay, since there may be serious consequences for the patient otherwise. Such time series show trends, slope changes and sudden level shifts, and they are overlaid by strong noise and many measurement artefacts. The development of update algorithms and the resulting increase in computational speed allows to apply robust regression techniques to moving time windows for online signal extraction. By simulations and applications we compare the performance of least median of squares, least trimmed squares, repeated median and deepest regression for online signal extraction.     

Enantioselective synthesis of (R)- and (S)-5-dimethylaminomethyl-4,5-dihydro-2(3H)-furanone methobromide - constrained analogues of acetylcholine

S6 and R6 represent constrained analogues of acetylcholine. Two effective routes to synthesize the enantiopure title compounds starting from either D- or L- glutamic acid are reported.