2,3,5,6-Tetramethylmorpholine: II—1H n.m.r. structural studies of the isomers of 2,3,5,6-tetramethylmorpholine

The structures of the six isomers of 2,3,5,6-tetramethyl-morpholine have been determined by means of proton nuclear magnetic resonance studies at 100 MHz. The spectra have been analysed in terms of spin–spin coupling constants and population distributions of the possible conformers at low temperatures. Also included in this paper are results from n.m.r. studies on the six 4-benzyl-2,3,5,6-tetramethylmorpholine derivatives, which give information about the stereochemistry of the methyl groups α to the amine group.     

Molecular adjustment of the electronic properties of nanoporous electrodes in dye-sensitized solar cells

Molecular modification of dye-sensitized, mesoporous TiO2 electrodes changes their electronic properties. We show that the open-circuit voltage (V(oc)) of dye-sensitized solar cells varies linearly with the dipole moment of coadsorbed phosphonic, benzoic, and dicarboxylic acid derivatives. A similar dependence is observed for the short-circuit current density (I(sc)). Photovoltage spectroscopy measurements show a shift of the signal onset as a function of dipole moment. We explain the dipole dependence of the V(oc) in terms of a TiO2 conduction band shift with respect to the redox potential of the electrolyte, which is partially followed by the energy level of the dye. The I(sc) shift is explained by a dipole-dependent driving force for the electron current and a dipole-dependent recombination current.     

Indications about the shape of the universe from the Wilkinson microwave anisotropy probe data

It is shown that the recent observations of NASA's Explorer mission, "Wilkinson Microwave Anisotropy Probe," hint that our Universe may possess a nontrivial topology. As an example we discuss the Picard space which is stretched out into an infinitely long horn but with finite volume.     

Test of the isotropy of the speed of light using a continuously rotating optical resonator

We report on a test of Lorentz invariance performed by comparing the resonance frequencies of one stationary optical resonator and one continuously rotating on a precision air bearing turntable. Special attention is paid to the control of rotation induced systematic effects. Within the photon sector of the standard model extension, we obtain improved limits on combinations of 8 parameters at a level of a few parts in 10(-16). For the previously least well known parameter we find [EQUATION: SEE TEXT]. Within the Robertson-Mansouri-Sexl test theory, our measurement restricts the isotropy violation parameter [EQUATION: SEE TEXT]. corresponding to an eightfold improvement with respect to previous nonrotating measurements.     

Undecidable Classical Properties of Observers

A property of a system is called actual, if the observation of the outcome of the test that pertains to that property yields an affirmation with certainty. We formalize the act of observation by assuming the outcome itself is an actual property of the state of the observer after the act of observation and correlates with the state of the system. For an actual property this correlation needs to be perfect. A property is called classical if either the property or its negation is actual. We show by a diagonal argument that there exist classical properties of an observer that he cannot observe perfectly. Because states are identified with the collection of properties that are actual for that state, it follows no observer can perfectly observe his own state. Implications for the quantum measurement problem are briefly discussed. PACS: 02.10-v, 03.65.Ta     

Direct versus conjugate addition to a terphenyl substituted alkynyl difluoro silane

Alkynyl difluoro silanes can react with nucleophiles either directly at the silane unit by displacing the fluorine atoms (direct addition) or, in contrast, the nucleophile can attack the β -carbon of the adjacent alkynyl group (conjugate addition). By using this type of conjugate addition a number of fascinating unsaturated silicon and germanium compounds have been prepared in the past using alkyl substituted phenyl groups as substituents. Therefore we wanted to investigate which regioselectivity isobserved in the case of such an alkynyl difluoro silane shielded by a terphenyl substituent (Mes₂C₆H₃-, Mes =2,4,6-trimethylphenyl). Surprisingly, the reaction with phenyl lithium leads exclusively to direct displacement rather than conjugate addition, which we could prove by X-ray crystallography of 5. Moreover, the synthesis, spectroscopic data and crystal structures of important intermediates to the starting alkynyl difluoro terphenyl silane 2 are presented.