Iron‐Mediated Electrophilic Amination of Organozinc Halides using Organic Azides

A wide range of alkyl‐, aryl‐ and heteroarylzinc halides were aminated with highly functionalized alkyl, aryl, and heterocyclic azides. The reaction proceeds smoothly at 50 °C within 1 h in the presence of FeCl3 (0.5 equiv) to furnish the corresponding secondary amines in good yields. This method was extended to peptidic azides and provided the arylated substrates with full retention of configuration. To demonstrate the utility of this reaction, we prepared two amine derivatives of pharmaceutical relevance using this iron‐mediated electrophilic amination as the key step

Incommensurate spin correlations in highly oxidized cobaltates La2−x_{2-x}Srx_{x}CoO4_{4}

We observe quasi-static incommensurate magnetic peaks in neutron scattering experiments on layered cobalt oxides La2-xSrxCoO4 with high Co oxidation states that have been reported to be paramagnetic. This enables us to measure the magnetic excitations in this highly hole-doped incommensurate regime and compare our results with those found in the low-doped incommensurate regime that exhibit hourglass magnetic spectra. The hourglass shape of magnetic excitations completely disappears given a high Sr doping. Moreover, broad low-energy excitations are found, which are not centered at the incommensurate magnetic peak positions but around the quarter-integer values that are typically exhibited by excitations in the checkerboard charge ordered phase. Our findings suggest that the strong inter-site exchange interactions in the undoped islands are critical for the emergence of hourglass spectra in the incommensurate magnetic phases of La2-xSrxCoO4.Comment: http://www.nature.com/articles/srep25117

Hour-glass magnetic excitations induced by nanoscopic phase separation in cobalt oxides La2−x_{2-x}Srx_xCoO4_4

The magnetic excitations in the cuprate superconductors might be essential for an understanding of high-temperature superconductivity. In these cuprate superconductors the magnetic excitation spectrum resembles an hour-glass and certain resonant magnetic excitations within are believed to be connected to the pairing mechanism which is corroborated by the observation of a universal linear scaling of superconducting gap and magnetic resonance energy. So far, charge stripes are widely believed to be involved in the physics of hour-glass spectra. Here we study an isostructural cobaltate that also exhibits an hour-glass magnetic spectrum. Instead of the expected charge stripe order we observe nano phase separation and unravel a microscopically split origin of hour-glass spectra on the nano scale pointing to a connection between the magnetic resonance peak and the spin gap originating in islands of the antiferromagnetic parent insulator. Our findings open new ways to theories of magnetic excitations and superconductivity in cuprate superconductors.Comment: Nature Communications 5, 5731 (2014

Electronic and magnetic nano phase separation in cobaltates La2−x_{2-x}Srx_{x}CoO4_4

The single-layer perovskite cobaltates have attracted enormous attention due to the recent observation of hour-glass shaped magnetic excitation spectra which resemble the ones of the famous high-temperature superconducting cuprates. Here, we present an overview of our most recent studies of the spin and charge correlations in floating-zone grown cobaltate single crystals. We find that frustration and a novel kind of electronic and magnetic nano phase separation are intimately connected to the appearance of the hour-glass shaped spin excitation spectra. We also point out the difference between nano phase separation and conventional phase separation.Comment: * plenary talk SUPERSTRIPES conference 201

Dual Conformal Properties of Six-Dimensional Maximal Super Yang-Mills Amplitudes

We demonstrate that the tree-level amplitudes of maximal super-Yang-Mills theory in six dimensions, when stripped of their overall momentum and supermomentum delta functions, are covariant with respect to the six-dimensional dual conformal group. Using the generalized unitarity method, we demonstrate that this property is also present for loop amplitudes. Since the six-dimensional amplitudes can be interpreted as massive four-dimensional ones, this implies that the six-dimensional symmetry is also present in the massively regulated four-dimensional maximal super-Yang-Mills amplitudes.Comment: 20 pages, 3 figures, minor clarification, references update

Characterization of an antioxidant and antimicrobial extract from cool climate, white grape marc

Valorization of agricultural waste has become increasingly important. Wastes generated by wineries are high in phenolic compounds with antioxidant and antibacterial properties, which contribute to phytotoxicity, making their immediate use for agricultural means limited. Utilizing a water-based extraction method, the phenolic compounds from winery waste were extracted and purified. The resulting extract was characterized for phenolic composition using high-pressure liquid chromatography-ultraviolet/visible and electrochemical detectors (HPLC-UV/Vis, ECD) for monomers, and spectral assessment of the tannins present using attenuated total reflectance-Fourier transform infrared (ATR-FTIR), FT-Raman, and solid-state nuclear magnetic resonance (SSNMR) spectroscopies. The extract\u2019s antioxidant activity was assessed by the scavenging of the 2,2-diphenyl-1\u2013picrylhydrazyl (DPPH) radical and Folin-Ciocalteu total phenolic assay, and was found to be as effective as a commercially obtained grape extract. The extract\u2019s antimicrobial efficacy was tested for minimum bactericidal concentration using Candida albicans, Escherichia coli 25922, and Staphylococcus aureus 6538, which resulted in greater efficacy against gram-positive bacteria as shown over gram-negative bacteria, which can be linked to both monomeric and tannin polyphenols, which have multiple modes of bactericidal action

KxFe2-ySe2 single crystals: Floating-zone growth, Transport and Structural properties

Single crystals of superconducting KxFe2-ySe2 have been grown with the optical floating-zone technique under application of 8 bar of argon pressure. We found that large and high quality single crystals with dimensions of ~\varnothing6 \times 10 mm could be obtained at the termination of the grown ingot through quenching, while the remaining part of the ingot decomposed. As-grown single crystals commonly represent an intergrowth of two sets of the c-axis characterized by slightly different lattice constants. Single crystal of K0.80Fe1.81Se2 shows a superconducting transition at Tc = 31.6 K, leading to a near 100% expulsion of the external magnetic field in magnetization measurements. On the other hand, neutron-diffraction data indicate that superconductivity in the sample coexists with a iron-vacancy superstructure and static antiferromagnetic order. The anisotropic ratio of the upper critical field Hc2 for both H//c and H//ab configurations is \sim3.46

The Transit Light Curve Project. IV. Five Transits of the Exoplanet OGLE-TR-10b

We present I and B photometry of five distinct transits of the exoplanet OGLE-TR-10b. By modeling the light curves, we find the planetary radius to be R_P = 1.06 +/- 0.08 R_Jup and the stellar radius to be R_S = 1.10 +/- 0.07 R_sun. The uncertainties are dominated by statistical errors in the photometry. Our estimate of the planetary radius is smaller than previous estimates that were based on lower-precision photometry, and hence the planet is not as anomalously large as was previously thought. We provide updated determinations of all the system parameters, including the transit ephemerides.Comment: Accepted in the Astrophysical Journal, 23 October 2006. Includes observations of additional transits to confirm earlier results. [15 pg, 6 figs