Diastereoselective Friedel-Crafts alkylation of indoles with chiral alpha-phenyl benzylic cations. Asymmetric synthesis of anti-1,1,2-triarylalkanes

The reactions of chiral benzyl carbocations bearing alpha-phenyl substituents with N-sulfonylated indoles afford 1,1,2-triarylalkanes with anti-selectivities. This outcome is a reversal of facial diastereoselectivity relative to Bach's alpha-alkyl-bearing benzyl cations. The reactions are promoted by either a Br?nsted acid (TFA) or Lewis acid (BF3.OEt2), offering differential diastereoselectivities and reactivities. The electronic properties of both reacting partners strongly influence the reaction rates and the product diastereoselectivities and appear to operate under kinetic control. This chemistry provides an efficient access to sterically congested tetrasubstituted ethanes.     

An optical image stabilisation using a droplet manipulation on a liquid crystal and polymer composite film

ABSTRACT

We demonstrate an image system with an optical image stabilisation using a droplet manipulation on a liquid crystal (LC) and polymer composite film (LCPCF) to reduce motion blur while preserve image quality. Such an image system adopts a liquid lens on an LCPCF and the mechanism is on a basis of droplet movement on LCPCF whose position changes because electrically tunable orientations of LC molecules on the surface of LCPCF. The change of position of the liquid lens compensates the deviation of light as the image system is under a handshake vibration. As a result, the image system under handshake vibrations could keep a clear image. The operating principles are introduced, and the experiments are performed and discussed. The concept in this paper can also be extended to design other optical components for modulating direction of light.     

A computational study of organic polyradicals stabilized by chromium atoms

Density functional theory has been used to investigate the properties of organic high spin molecules. The M05/cc-pVDZ calculations predict a septet ground state for the 2,3,6,7,10,11-hexahydro-1,4,5,8,9,12-hexaoxocoronene-2,3,6,7,10,11-hexayl radical (coronene-6O). The computations show further that the formation of intermolecular carbon-carbon bonds yields a singlet ground state for the dimer rather than a possible tridectet state as expected from the monomer's multiplicity. A benzene molecule placed between coronene-6O molecules leads to the desired high-spin cluster, but the overall stability of the cluster is low. A chromium atom inserted between two peripheral C(6) rings of coronene-6O yields a sandwich structure with the expected tridectet ground state and a binding energy which is 15 times larger than the corresponding tridectet dimer stabilized by a benzene molecule. The presented DFT calculations suggest that a chromium atom can effectively link organic polyradicals to larger magnetic units.     

Brill transition of nylon-6 in electrospun nanofibers

Electrospun nylon-6 fibers were prepared from its polyelectrolyte solution in formic acid with different concentrtaions. In situ Fourier transform infrared (FTIR), wide-angle X-ray diffraction and small-angle X-ray scattering (SAXS) were performed on the nylon-6 fibers heated to various temperatures until melting. For comparison, stepwise annealing of the solution-cast film having exclusively the α-form was also carried out to elucidate the structural evolution. Our results showed that Brill transition in the electrospun fibers occurs at a lower temperature than that in the solution-cast film due to the crystal size difference. Differential scanning calorimetry heating traces on the as-spun fibers exhibited a unique crystalline phase with a melting temperature of ～235?°C, higher than the equilibrium melting temperature of nylon-6. The content of high melting temperature (HMT) phase increased with increasing nylon-6 concentration; a maximum of 30?% of the fiber crystallinity was reached for fibers obtained from the 22?wt.% solution regardless of the heating rates used. Based on the SAXS and FTIR results, we speculated that the HMT phase is associated with thick α-form crystals developed from the highly oriented nylon-6 chains that are preserved in the skin layer of the as-spun fibers. A plausible mechanism for the formation of the skin/core fiber morphology during electrospinning was proposed.     

Estimation of intra-cluster correlation coefficient via the failure of Bartlett’s second identity

A new means of estimating the correlation coefficient for cluster binary data in the regression settings is introduced. The creation of this method is founded upon the violation of Bartlett’s second identity when adopting the binomial distributions to model binary data that are correlated. The new methodology applies to any sensible link functions that connect the success probability and covariates. One can easily implement the procedure by using any statistical software providing the naïve and the sandwich covariance matrices for regression parameter estimates. Simulations and real data analyses are used to demonstrate the efficacy of our new procedure.     

Intrinsic equations for a generalized relaxed elastic line on an oriented surface in the galilean space

In this article, we derive the intrinsic equations for a generalized relaxed elastic line on an oriented surface in the Galilean 3-dimensional space G₃. These equations will give direct and more geometric approach to questions concerning about generalized relaxed elastic lines on an oriented surface in G₃.     

Possible anomalies in Higgs decay: charm-suppression and flavour-violation

It is suggested that the Higgs boson may have a branching ratio into the $c\bar{c}$ mode suppressed by several orders of magnitude compared with conventional predictions and in addition some small but detectable flavour-violating modes such as $b\bar{s}$ and $\tau \bar{\mu}$ . The suggestion is based on a scheme proposed and tested earlier for explaining the mixing pattern and mass hierarchy of fermions in terms of a rotating mass matrix. If confirmed, the effects would cast new light on the geometric origin of fermion generations and of the Higgs field itself.     

Lentivirus-mediated transgene delivery to the hippocampus reveals sub-field specific differences in expression

Background  

In the adult hippocampus, the granule cell layer of the dentate gyrus is a heterogeneous structure formed by neurons of different ages, morphologies and electrophysiological properties. Retroviral vectors have been extensively used to transduce cells of the granule cell layer and study their inherent properties in an intact brain environment. In addition, lentivirus-based vectors have been used to deliver transgenes to replicative and non-replicative cells as well, such as post mitotic neurons of the CNS. However, only few studies have been dedicated to address the applicability of these widespread used vectors to hippocampal cells in vivo. Therefore, the aim of this study was to extensively characterize the cell types that are effectively transduced in vivo by VSVg-pseudotyped lentivirus-based vectors in the hippocampus dentate gyrus.     

Compatible domain arrangements and poling ability in oriented ferroelectric films

The microstructure in single crystal ferroelectric films is significantly affected by the substrate conditions and the crystallographic orientation of the film. Domain arrangements form to minimize the total energy producing a stable state corresponding to the external boundary conditions. In order to find low energy domain arrangements, this study uses exact compatibility conditions for periodic laminate structures which ensure that all the adjacent domains fit together compatibly. These conditions are applied to films with various orientations and crystal systems, such as the rhombohedral and tetragonal crystal systems. A systematic search is used to discover exactly compatible structures for given states of macroscopic strain and polarization in the film. The theory is applied to [001], [011], and [111] oriented rhombohedral and tetragonal films. The results indicate poling paths along which the microstructure can evolve continuously while maintaining compatibility, to get from a state of zero through-thickness polarization to the state with the greatest value of through-thickness polarization. The evolution of the domain arrangement along these poling paths is shown, and the poling ability, or the limit on the maximum polarization achieved, is discussed. The influence of a strain state imposed by the substrate on the microstructure and poling ability is studied. The use of the model is illustrated by developing poling maps for a tetragonal [001] oriented film to show the set of polarization states that can be achieved as a function of the imposed substrate strain.