Carbon-13 Assignments and Revision of the Stereostructures of the Cadinanes 2-Hydroxy-8α-angeloyloxycalamenene and 2-Hydroxy-8α-hydroxycalamenene

The two known cadinanes 2-hydroxy-8α-hydroxycalamenene and 2-hydroxy-8α-angeloyloxycalamenene were isolated from a Louisiana population of Heterotheca subaxillaris.

Their ¹³C NMR spectra were fully assigned by the application of HETCOR, COLOC, COSY, NOESY and DEPT experiments. It was shown on the basis of NOESY experiments that both cadinanes require revision at the stereogenic centre C-7.     

A novel monochromator for experiments with ultrashort X‐ray pulses

Aiming at advancing storage‐ring‐based ultrafast X‐ray science, over the past few years many upgrades have been undertaken to continue improving beamline performance and photon flux at the Femtoslicing facility at BESSY II. In this article the particular design upgrade of one of the key optical components, the zone‐plate monochromator (ZPM) beamline, is reported. The beamline is devoted to optical pump/soft X‐ray probe applications with 100 fs (FWHM) X‐ray pulses in the soft X‐ray range at variable polarization. A novel approach consisting of an array of nine off‐axis reflection zone plates is used for a gapless coverage of the spectral range between 410 and 1333 eV at a designed resolution of E/ΔE = 500 and a pulse elongation of only 30 fs. With the upgrade of the ZPM the following was achieved: a smaller focus, an improved spectral resolution and bandwidth as well as excellent long‐term stability. The beamline will enable a new class of ultrafast applications with variable optical excitation wavelength and variable polarization.     

Effect of gasketing and assembly design: a novel 10/3.5 mm multi-anvil assembly reaching perovskite pressures

A new design of multi-anvil assembly and modified gasket characteristics with octahedron and truncation edge lengths of 10 and 3.5 mm is presented for reaching pressures and temperatures over 24 GPa and 2000 °C, respectively. Partially dehydroxylated pyrophyllite half-gaskets with a tapered design fully nesting the octahedron have been employed to prevent excessive octahedron extrusion between the cubes. The assembly utilizes an axially placed thermocouple through the octahedral center, allowing two samples to be present at identical high P–T conditions on either side of the thermocouple during a run. A third sample can be used as a packing around the thermocouple, so long as that sample is inert with respect to the thermocouple and surrounding material. The temperature gradient within the sample locations has been well characterized using two-pyroxene thermometry in the CaO–MgO–SiO₂ system and numerical modeling calculations. The results indicate a good agreement in gradient shape, although the numerical model appears to under-estimate the magnitude of temperature change. The assembly maintains stable temperatures and provides low failure rates.     

Equation of state of CaMnO3: a combined experimental and computational study

Elastic properties of CaMnO₃ are of primary importance in the science and technology of CaMnO₃-based perovskites. From X-ray diffraction experiments performed at pressures up to 100 kbar using a diamond-anvil cell to hydrostatically compress our sample, a bulk modulus, K ₀, of 1734(96) kbar was obtained after fitting parameters to the third-order Birch–Murnaghan equation of state. Mean field, semiclassical simulations predict, for the first time, the third-order equation-of-state parameters and show how the bulk modulus increases with pressure (the zero pressure value being 2062.1 kbar) and decreases with the extent of nonstoichiometry caused by the formation of oxygen vacancies. These trends are amplified for the shear modulus. A more accurate model that allows for the explicit reduction of Mn ions, or localization of excess electrons, yields qualitatively similar results. The experimental and calculated axial ratios show the same trends in their variation with rising pressure.     

Characterization of silicon nanowires grown on silicon, stainless steel and indium tin oxide substrates

Silicon nanowires (SiNWs) have been grown on crystalline silicon (Si), indium tin oxide (ITO) and stainless steel (SS) substrates using a gold catalyst coating with a thickness of 200 nm via pulsed plasma-enhanced chemical vapor deposition (PPECVD). Their morphological, mineralogical and surface characteristics have been investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman analysis. SiNWs growth is accompanied by oxidation, thus yielding partially (SiO _x ) and fully oxidized (SiO₂) Si sheaths. The mean diameters of these SiNWs range from 140 to 185 nm. Si with (111) and (220) planes exists in SiNWs grown on all three substrates while Si with a (311) plane is detected only for Si and ITO substrates. Computational simulation using density functional theory (DFT) has also been conducted to supplement the experimental Raman analyses for crystalline Si and SiO₂. XPS results reveal that ca. 30 % of the SiNWs have been oxidized for all substrates. The results presented in this paper can be used to aid selection of appropriate substrates for SiNW growth, depending on specific applications.     

Measurement of the pH value in pork meat early postmortem by Raman spectroscopy

The pH of a muscle is an accepted parameter to identify normal and deviating meat qualities. In this work, Raman spectroscopy is shown to be suitable for the non-invasive measurement of the early postmortem pH of meat. Raman spectra of ten pork semimembranosus muscles were recorded with a portable handheld device 0.5–24 h postmortem. The spectra were correlated with pH and lactate kinetics measured in parallel. Seven of the muscles were normal, two exhibited accelerated glycolysis and one showed absence of acidification. The pH decline with time could be calculated from the Raman spectra with the Henderson–Hasselbalch equation using only two signals of phosphate vibrations at 980 and 1,080 cm^?1 with a close correlation for each muscle, but larger variations between animals. More robust and better correlations for all muscles were obtained with a linear model based on 11 signals from lactate, lactic acid, phosphate, a carbonyl band and nucleotides resulting in R ² = 0.78 and RMSECV = 0.2 or a partial least-square model using the complete spectrum (R ² = 0.94 and RMSECV = 0.2). These results show the potential of Raman spectroscopy for an online detection of the pH and thus meat qualities during meat processing.     

Synthèse d'analogues furanniques et nitro-2 furanniques du diméthyl-7,12 benzanthracène

A route to 1-formyl-2-hydroxy-9-methylanthracene and 1-formy 1-2-hydroxy-9,10-dimethylanthracene is desribed. These two aldehydes were further converted into mono- or dimethylanthra[2,1-b]furans, besides the corresponding acids and esters, by condensation with ethyl bromoacetate. The related mono- or dimethyl-2-nitroanthra[2,1-b]furans were also prepared by reaction between the above aldehydes and bromonitromethane, followaed by heating in toluene in the presence of p-toluene-sulfonic acid.     

From Y- to Siamese-twin shaped glycolipids

Summary A set of Y-shaped and Siamese-twin shaped carbohydrate based glycolipids was investigated using polarising microscopy. The structure was changed from the normal type (1 head, two chains) to complex inverted structures (2 heads outside 1 to 3 chains in the middle part). The carbohydrate headgroup was changed from mono- to disaccharide; also the alkyl chain length was varied systematically. The compounds displayed different thermotropic mesophases (Smectic A phases, columnar phases and cubic phases) depending on the type of carbohydrate headgroup and the alkyl chain length.     

Planar subgroup lattices

In this paper we determine all finite groups with planar subgroup lattices. For this, by Kuratowski’s theorem, we have to study subdivisions of the Kuratowski graphs K_3,3 and K₅ in the covering graph of the subgroup lattice of a finite group. It turns out that such a graph is planar if and only if it contains no subdivision of K_3,3. Received April 28, 2005; accepted in final form August 28, 2005.     

Determination of Platinum-Group Elements (PGE) from catalytic converters in soil by means of docimasy and INAA

The nickelsulfide fire assay (docimasy) for the enrichment of platinum-group elements (PGEs) has been modified for the use with small samples and combined with instrumental neutron-activation analysis (INAA). This procedure has been applied to the determination of PGEs exhausted from catalytic converters and deposited in soil near the Wiesbadener Kreuz (highway A3, Frankfurt-Köln). Our results show a considerable enhancement of the Pt (up to 330 ng/g), Pd (6.6 ng/g) and Rh (7.5 ng/g) contents close to the highway.