Novel 10-Hydroxydocosapolyenoic Acids from Deep-Water Scleractinian Corals

The new 10-hydroxydocosapolyenoic acids (10R,7Z,11E,13E,16Z,19Z)-10-hydroxydocosa-7,11,13,16,19-pentaenoic acid ( 1a ) and (10R*,4Z,7Z,11E,13Z,16Z,19Z)-10-hydroxydocosa-4,7,11,13,16,19-hexaenoic acid ( 2a ) were isolated as methyl esters 1b and 2b , respectively, following CH₂N₂ treatment of the EtOH extract of the scleractinian coral Madrepora oculata from deep-water of the southern Indian Ocean. From the same species from the Norwegian Sea, 1b and the methyl ester 3b of the new (10R,7Z,11E,13Z,16Z)-10-hydroxydocosa-7,11,13,16-tetraenoic acid ( 3a ) were analogously isolated, while from the untreated extract, the free acid 3a itself could be isolated. The absolute configuration of 1a and 3a was established by the chiral exciton coupling of the C(10) benzoate esters 1c and 3c . Other known 10-hydroxydocosapolyenoic acids and 8-hydroxyeicosapolyenoic acid were also isolated from M. oculata from both locations. These results imply the intervention of a rare lipooxygenase with high ω13 specificity. In an examination of several other deep-water scleractinians, hydroxypolyenoic acids were found only in Lophelia pertusa from the northeastern Atlantic Ocean.     

Conformational structures, energies, rotational barrier heights and torsional force constants in halogenated methyl-silanes obtained by molecular-mechanics calculations

Conformational structures, energies, barrier heights and torsional force constants in halogenated (F, Cl, Br) methyl-silanes have been obtained by molecular-mechanics calculations. A comparison of the ethan-like molecules with central bonds C---C, Si---C and Si---Si has been made. It is predicted that, for halogenated methyl-silanes, the difference in conformational energy between anti and gauche conformers is small.     

The molecular structure and conformation of 1,2-cyclononadiene

The molecular structure and conformation of 1,2-cyclononadiene has been studied by the gas electron diffraction method. The experimental data were interpreted in terms of an unsymmetrical (C₁) molecular model and there were no indications of other conformers being present.     

Atomistic and electronic structure of bimetallic cobalt/rhenium clusters from density functional theory calculations

We have carried out computational density functional investigations of Co I Re J (J=0,1,2; I+J=14) metal atom clusters. Through thorough optimization of geometry, spin polarization, and electronic configuration, the most stable structures for each cluster have been identified. While the global minima are found to be well defined and energetically well separated from other local minima, the study reveals a plethora of different structures and symmetries only moderately higher in energy. A key point of interest is the effect of doping the cobalt clusters with rhenium. Aside from significant structural reorganizations, rhenium is found to stabilize the clusters and couple down the spin. Furthermore, the most stable clusters comprise highly coordinated rhenium and, in the case of Co 12 Re 2, Re-Re bonding. Our results are compared to earlier experimental and computational data.     

Measuring and simulating morphology gradients in injection‐molded talc‐reinforced isotactic polypropylene

Injection molded polymer parts are known to exhibit structural gradients of crystallinity, crystallite phases and crystallite orientations. The structural variations depend on the geometry, the material properties, and the processing conditions, and affect the mechanical properties of the molded part. We explore the use of raster‐scanning small‐ and wide‐angle X‐ray scattering (SAXS, WAXS) for mapping the microstructure in dogbone specimens of an isotactic polypropylene (PP) homopolymer and a talc‐reinforced isotactic PP compound. The specimens were injection molded with different mold temperatures and injection speeds, and the mapping approach revealed systematic structural heterogeneities and asymmetries. Accompanying numerical simulations of the injection molding process yielded predictions of the flow pattern, including the shear rate distribution and the resulting orientation of the flake‐shaped talc particles. We found a clear correspondence between the experimentally observed data and the simulations, in particular regarding the asymmetry of the orientation distributions relative to the center of the dogbone cross section, caused by asymmetric flow through the entrance of the mold. Furthermore, the shear rate distribution correlated with the occurrence of α‐ and β‐phases. Subtle differences in the crystallized structures along the long axis of the dogbones suggest an explanation to the observation that the specimens studied always tended to break at the same position in tensile tests. The results clearly demonstrate the potential of mapping experiments which combine lateral resolution on macroscopic length scales with the molecular‐scale resolution from scattering. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1157–1167     

A velocity dependent effective angle method for calibration of X-probes at low velocities

A velocity dependent effective angle (VDEA) method for the calibration of yaw response of hot-wire X-probes at low flow velocities (0.5–6 m/s) is presented. Comparisons with a full velocity vs. yaw-angle method (Österlund 1999) in a smooth wall channel flow indicate that there is only moderate advantage in using the latter method, which is considerably more laborious. Comparisons with direct numerical simulations (DNS) (Moser et al. 1999) and the more common fixed effective angle method (FEA) show that the VDEA method significantly improves estimates of Reynolds stresses compared to the FEA method.     

The molecular structure of 1-methyl-trans-cyclooctene

The molecular structure of 1 -methyl-trans-cyclooctene has been studied by the gas electron diffraction method. A molecular mechanics calculation has been done for the title compound and for trans-cyclooctene and 1,2-dimethyl-trans-cyclooctene.     

The molecular structure and conformation of 1,2,6-cyclononatriene

The molecular structure and conformation of 1,2,6-cyclononatriene were studied by the gas electron diffraction method. Two different models, differing primarily in the degree of distortion from planarity of the bonds at the isolated CC double bond, give satisfactory agreement with the experimental data.