Verbesserungen von Wagen

Ohne Zusammenfassung     

Synthesis of rel-(3RS,3aSR,7aSR)-3-(4-Chlorophenyl)-3a,4,5,6,7,7a-hexahydro-1-methylindolin-6-one,the Main Metabolite of the Analgesic Ro 15-8081: A Potent Amine-Uptake Inhibitor

The synthesis of the title compound 2 and its diastereoisomer 3 was accomplished using tricarbonyl[1-5-n-(4-methoxycyclohexa-2,4-dien-1-yl)]iron tetrafluoroborate ( 4 ) as a precursor to the cyclohexanone ring. The assignments of the relative configurations of 2 and 3 are based on the X-ray analysis of compound 3 . Both compounds 2 and 3 are potent inhibitors of neuronal noradrenaline uptake in rats with similar potencies in vitro as compared to amitriptyline and desipramine. Compounds 2 and 3 are less potent as serotonin-uptake inhibitors, very weak inhibitors of dopamine uptake, and virtually devoid of antinociceptive activity.     

Fullerodendrimers with peripheral triethyleneglycol chains

Triethylene glycol terminated poly(aryl ether) dendritic branches with an aldehyde function at the focal point have been prepared and attached to C₆₀ by a 1,3-dipolar cycloaddition.     

Redox state of the photosynthetic electron transport chain in wild-type and mutant leaves of Arabidopsis thaliana: Impact on photosystem II fluorescence

In addition to the photosynthetic linear electron transport, several alternative electron transport routes exist in thylakoids of higher plants. The plastoquinone (PQ) pool acts as a common electron carrier in these pathways. In the cyclic electron flow around photosystem I (PSI), reduced ferredoxin is used by the ferredoxin-quinone reductase (FQR) to reduce the PQ pool. Chlororespiratory pathway consists in the reduction of the PQ pool by the NAD(P)H dehydrogenase (NDH). These alternative pathways and their role in photosynthesis are still not fully understood. In the present study, the accumulation kinetics of quinone acceptors was measured by fluorescence induction in leaves of Arabidopsis thaliana wild-type and mutants altered in alternative electron pathways after various light- and dark-adaptation conditions. Results show that NDH activity can be probed by fluorescence induction during light-to-dark transition of plants. Also, the activity of FQR pathway did not affect directly the FI kinetics. However, the accumulation kinetics of reduced PQ under actinic light was dependant on the redox state of PSI acceptors prior to illumination.     

Light-induced degradation of the active layer of polymer-based solar cells

Polymer-based organic solar cells are known to offer a poor stability in real use conditions, and the photodegradation of the active organic layer plays an important role in the reduced lifetime of the devices. This paper focuses on the photodegradation of two conjugated polymers used in organic solar cells, namely poly(2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene (MDMO-PPV) and poly(3-hexyylthiophene) (P3HT), and their blends with [60]PCBM (methano-fullerene[6,6]-phenyl C61-butyric acid methyl ester), a fullerene derivative. MDMO-PPV and P3HT thin films were submitted to photoageing (λ > 300 nm) in the presence and in the absence of oxygen. The mechanisms by which these polymers degrade were elucidated. P3HT, pristine and blended with PCBM, was shown to be much more stable under illumination than MDMO-PPV. The results showed that, if deposited on an inert substrate and well protected from oxygen with a convenient encapsulation, P3HT:PCBM based active layer should be intrinsically stable for several years in use conditions.     

Selection of suitable operating conditions to minimize the gradient equilibration time in the separation of drugs by Ultra-High-Pressure Liquid Chromatography with volatile (mass spectrometry-compatible) buffers

Reversed phase gradient elution is the method of choice for pharmaceuticals analysis since it allows reducing the analysis time while improving both the quality of the separation and the detection limits. The current trends are towards faster separations which can be achieved thanks to equipments withstanding ultra-high pressures and/or high temperatures. Under such conditions, gradient separations can be carried out within a few minutes or even a few tens of seconds. A long equilibration time in addition to the gradient time can be therefore very detrimental. In this work, we investigated the extent to which the gradient equilibration time can be reduced and which parameters mainly affect the retention variability of ionizable compounds when using volatile buffers. We first found out an excellent repeatability between run-to-run experiments whatever the equilibration time and the operating conditions. We then pointed out the key operating parameters which allow achieving reproducible runs when varying the equilibration time between runs. With a view of reducing the equilibration time, the effects of various conditions were examined. The latter include the type of additive for mobile phase pH adjustment, the initial eluent composition, the type of stationary phase, the temperature and the flow-rate. Although much remains to be understood about the equilibration process, our study allows making progress in the knowledge of this phenomenon. Based on the present results, a beneficial effect of both temperature and flow-rate was highlighted and operating conditions leading to faster column equilibration are suggested.     

Influence of deposition conditions on the optical properties of erbium-doped yttrium oxide films grown by aerosol-UV assisted MOCVD

Erbium-doped Y₂O₃ films were prepared by aerosol-UV assisted metal-organic chemical vapour deposition (MOCVD) at 410 °C. The effects of humidity of carrier gas and UV-assistance on their structure and optical properties were investigated on the as-deposited and thermal annealed films using infrared spectroscopy, X-ray diffraction and transmission electron microscopy. It was found that the as-deposited Er:Y₂O₃ films crystallise in the Y₂O₃ cubic structure and present a very low organic contamination when the deposition takes place under high air humidity and, even better, with UV-assistance. After annealing, two different structural phases are observed corresponding to the cubic and the monoclinic structures of Y₂O₃. The Er³⁺ luminescence analysed in the visible and IR regions, shows the classical green transitions. The best optical properties were obtained with as-deposited and annealed Er:Y₂O₃ films grown under high air humidity with UV-assistance. Under such deposition conditions, ⁴I_13/2 lifetimes was found to be 3.07 and 6.1 ms for films annealed at 800 and 1000 °C, respectively, and up-conversion phenomena were underlined. This indicates that the deposition conditions, in particular air humidity, play an important role in the luminescent properties even after annealing.     

Ground state of the quasi-1D compound BaVS3 resolved by resonant magnetic x-ray scattering

Resonant magnetic x-ray scattering near the vanadium L2,3-absorption edges has been used to investigate the low temperature magnetic structure of high quality BaVS3 single crystals. Below T(N)=31 K, the strong resonance revealed a triple-incommensurate magnetic ordering at the wave vector (0.226 0.226 ξ) in hexagonal notation, with ξ=0.033. The azimuthal-angle dependence of the scattering signal and time-dependent density functional theory simulations indicate an antiferromagnetic order within the ab plane with the spins polarized along a in the monoclinic structure.     

Dynamical selection of the primordial density fluctuation amplitude

In inflationary models, the predicted amplitude of primordial density perturbations Q is much larger than the observed value (～10(-5)) for natural choices of parameters. To explain the requisite exponential fine-tuning, anthropic selection is often invoked, especially in cases where microphysics is expected to produce a complex energy landscape. By contrast, we find examples of ekpyrotic models based on heterotic M theory for which dynamical selection naturally favors the observed value of Q.     

Entangling different degrees of freedom by quadrature squeezing cylindrically polarized modes

Quantum systems such as, for example, photons, atoms, or Bose-Einstein condensates, prepared in complex states where entanglement between distinct degrees of freedom is present, may display several intriguing features. In this Letter we introduce the concept of such complex quantum states for intense beams of light by exploiting the properties of cylindrically polarized modes. We show that already in a classical picture the spatial and polarization field variables of these modes cannot be factorized. Theoretically it is proven that by quadrature squeezing cylindrically polarized modes one generates entanglement between these two different degrees of freedom. Experimentally we demonstrate amplitude squeezing of an azimuthally polarized mode by exploiting the nonlinear Kerr effect in a specially tailored photonic crystal fiber. These results display that such novel continuous-variable entangled systems can, in principle, be realized.