Soft x-ray resonant diffraction study of magnetic and orbital correlations in a manganite near half doping

We have utilized resonant x-ray diffraction at the Mn L(II,III) edges in order to directly compare magnetic and orbital correlations in Pr0.6Ca0.4MnO3. Comparing the widths of the magnetic and orbital diffraction peaks, we find that the magnetic correlation length exceeds that of the orbital order by nearly a factor of 2. Furthermore, we observe a large (approximately 3 eV) spectral weight shift between the magnetic and orbital resonant line shapes, which cannot be explained within the classic Goodenough picture of a charge-ordered ground state. To explain the shift, we calculate the orbital and magnetic resonant diffraction line shapes based on a relaxed charge-ordered model.     

Persistence of high-frequency spin fluctuations in overdoped superconducting La2-xSrxCuO4 (x=0.22)

We report a detailed inelastic neutron scattering study of the collective magnetic excitations of overdoped superconducting La(1.78)Sr(0.22)CuO(4) for the energy range 0-160 meV. Our measurements show that overdoping suppresses the strong response present for optimally doped La(2-x)Sr(x)CuO(4) which is peaked near 50 meV. The remaining response is peaked at incommensurate wave vectors for all energies investigated. We observe a strong high-frequency magnetic response for E approximately >80 meV suggesting that significant antiferromagnetic exchange couplings persist well into the overdoped part of the cuprate phase diagram.     

On the Dual Phosphorescence of Xanthone and Chromone in Glassy Hydrocarbon Hosts

Trace quantities of hydrogen‐bonding impurities in otherwise highly purified and dried glassy hydrocarbon matrices at 77 K can modify the relative triplet state energy levels, and hence the photophysical properties of two aromatic ketones, xanthone and chromone, to the extent that the intrinsic spectroscopic properties are obscured. The intrinsic spectroscopic properties of each are revealed in multicrystalline n‐alkane Shpol'skii matrices, and also can be observed in rigorously purified and dried hydrocarbon glasses at 77 K. The extreme sensitivity to stoichiometric, and even substoichiometric quantities of hydrogen‐bonding impurities arises from the near‐degeneracy of the two lowest‐lying triplet states, and the sensitive nature of the n→π* blueshift phenomena to specific hydrogen‐bonding interactions.     

Co-existence of long- and short-range magnetic correlations in holmium-erbium superlattices

The effect of competing crystal-field anisotropies on magnetic order has been investigated in a series of Ho/Er superlattices using a combination of x-ray and neutron scattering techniques. For temperatures in the interval T_N(Er)≤T≤T_N(Ho) the Ho basal-plane order propagates coherently through the paramagnetic Er over a typical length scale of 1000 Å. At low temperatures the Ho moments retain their bulk-like helical configuration, whereas the magnetic structure in the Er blocks has both basal-plane and c-axis components. Below T_N(Er), the coherence length of the basal-plane order decreases on cooling, while the longitudinal component of the Er moments fails to order across the Ho block. It is argued that these results require an extension of current models of indirect exchange in superlattices to explicitly include the superlattice band structure.     

Effects of Curcumin Analogues DMC and EF24 in Combination with the Cytokine TRAIL against Kidney Cancer

The natural compound curcumin has been shown to have therapeutic potential against a wide range of diseases such as cancer. Curcumin reduces cell viability of renal cell carcinoma (RCC) cells when combined with TNF-related apoptosis-inducing ligand (TRAIL), a cytokine that specifically targets cancer cells, by helping overcome TRAIL resistance. However, the therapeutic effects of curcumin are limited by its low bioavailability. Similar compounds to curcumin with higher bioavailability, such as demethoxycurcumin (DMC) and 3,5-bis(2-fluorobenzylidene)-4-piperidone (EF24), can potentially have similar anticancer effects and show a similar synergy with TRAIL, thus reducing RCC viability. This study aims to show the effects of DMC and EF24 in combination with TRAIL at reducing ACHN cell viability and ACHN cell migration. It also shows the changes in death receptor 4 (DR4) expression after treatment with these compounds individually and in combination with TRAIL, which can play a role in their mechanism of action.     

Dispersive excitations in the high-temperature superconductor La2-xSrxCuO4

High-resolution neutron scattering experiments on optimally doped La2-xSrxCuO4 (x=0.16) reveal that the magnetic excitations are dispersive. The dispersion is the same as in YBa2Cu3O6.85, and is quantitatively related to that observed with charge sensitive probes. The associated velocity in La2-xSrxCuO4 is only weakly dependent on doping with a value close to the spin-wave velocity of the insulating (x=0) parent compound. In contrast with the insulator, the excitations broaden rapidly with increasing energy, forming a continuum at higher energy and bear a remarkable resemblance to multiparticle excitations observed in 1D S=1/2 antiferromagnets. The magnetic correlations are 2D, and so rule out the simplest scenarios where the copper oxide planes are subdivided into weakly interacting 1D magnets.