Orbitally-driven Behavior: Mott Transition, Quantum Oscillations and Colossal Magnetoresistance in Bilayered Ca3Ru2O7

We report recent transport and thermodynamic experiments over a wide range of temperatures for the Mott-like system Ca3Ru2O7 at high magnetic fields, B, up to 30 T. This work reveals a rich and highly anisotropic phase diagram, where applying B along the a-, b-, and c-axis leads to vastly different behavior. A fully spin-polarized state via a first order metamagnetic transition is obtained for B||a, and colossal magnetoresistance is seen for B||b, and quantum oscillations in the resistivity are observed for B||c, respectively. The interplay of the lattice, orbital and spin degrees of freedom are believed to give rise to this strongly anisotropic behavior.Comment: 26 pages and 8 figure

Lagrange Model for the Chiral Optical Properties of Stereometamaterials

We employ a general Lagrange model to describe the chiral optical properties of stereometamaterials. We derive the elliptical eigenstates of a twisted stacked split-ring resonator, taking phase retardation into account. Through this approach, we obtain a powerful Jones matrix formalism which can be used to calculate the polarization rotation, ellipticity, and circular dichroism of transmitted waves through stereometamaterials at any incident polarization. Our experimental measurements agree well with our model.Comment: 10 pages, 3 figures, Theory and experimen

Valosin-containing protein regulates the proteasome-mediated degradation of DNA-PKcs in glioma cells.

DNA-dependent protein kinase (DNA-PK) has an important role in the repair of DNA damage and regulates the radiation sensitivity of glioblastoma cells. The VCP (valosine-containing protein), a chaperone protein that regulates ubiquitin-dependent protein degradation, is phosphorylated by DNA-PK and recruited to DNA double-strand break sites to regulate DNA damage repair. However, it is not clear whether VCP is involved in DNA-PKcs (DNA-PK catalytic subunit) degradation or whether it regulates the radiosensitivity of glioblastoma. Our data demonstrated that DNA-PKcs was ubiquitinated and bound to VCP. VCP knockdown resulted in the accumulation of the DNA-PKcs protein in glioblastoma cells, and the proteasome inhibitor MG132 synergised this increase. As expected, this increase promoted the efficiency of DNA repair in several glioblastoma cell lines; in turn, this enhanced activity decreased the radiation sensitivity and prolonged the survival fraction of glioblastoma cells in vitro. Moreover, the VCP knockdown in glioblastoma cells reduced the survival time of the xenografted mice with radiation treatment relative to the control xenografted glioblastoma mice. In addition, the VCP protein was also downregulated in ~25% of GBM tissues from patients (WHO, grade IV astrocytoma), and the VCP protein level was correlated with patient survival (R(2)=0.5222, P<0.05). These findings demonstrated that VCP regulates DNA-PKcs degradation and increases the sensitivity of GBM cells to radiation

The Flexible Group Spatial Keyword Query

We present a new class of service for location based social networks, called the Flexible Group Spatial Keyword Query, which enables a group of users to collectively find a point of interest (POI) that optimizes an aggregate cost function combining both spatial distances and keyword similarities. In addition, our query service allows users to consider the tradeoffs between obtaining a sub-optimal solution for the entire group and obtaining an optimimized solution but only for a subgroup. We propose algorithms to process three variants of the query: (i) the group nearest neighbor with keywords query, which finds a POI that optimizes the aggregate cost function for the whole group of size n, (ii) the subgroup nearest neighbor with keywords query, which finds the optimal subgroup and a POI that optimizes the aggregate cost function for a given subgroup size m (m <= n), and (iii) the multiple subgroup nearest neighbor with keywords query, which finds optimal subgroups and corresponding POIs for each of the subgroup sizes in the range [m, n]. We design query processing algorithms based on branch-and-bound and best-first paradigms. Finally, we provide theoretical bounds and conduct extensive experiments with two real datasets which verify the effectiveness and efficiency of the proposed algorithms.Comment: 12 page

Surface Decomposition of Doped PrBaMn₂O_5+δInduced by in Situ Nanoparticle Exsolution:Quantitative Characterization and Catalytic Effect in Methane Dry Reforming Reaction

The exsolution of metallic nanoparticles (NPs) from perovskite oxides is a promising strategy for synthesizing supported catalysts. The associated segregation of A-site cations on the surface is challenging to investigate experimentally and is often detrimental to the catalytic performance. In this work, we found that during the in situ exsolution of Ni-Co bimetallic nanoparticles from Pr0.45Ba0.45Mn1–x(Co1/3 Ni2/3)xO3±δ, A-site cation enrichment occurred on the surface when x is 0.1; yet, the perovskite surface decomposed when x reached 0.2, forming a thin layer comprising various nanocrystalline oxides, which partially blocked the active sites of the exsolved Ni-Co particles. A hydration and carbonation reaction facilitated the conversion of nanocrystalline BaO species into large and highly crystallized BaCO3 particles. This enabled the exposure of more Ni-Co active sites and offered a chance to quantify that the decomposed surface layer accounts for ∼7.2 wt % of the total perovskite. Because of this unique feature, the surface-decomposed catalyst showed higher activity in the dry methane reforming reaction with better stability. Importantly, the regeneration feature was not hampered as the complete exsolution-dissolution recyclability of the catalyst remained

Sequence Analysis of HindIII Q2 Fragment of Capripoxvirus Reveals a Putative Gene Encoding a G-Protein-Coupled Chemokine Receptor Homologue

AbstractThe DNA sequence of the HindIII Q2 fragment near the left terminus of the capripoxvirus (KS-1 strain) genome was determined. The sequence contains two complete open reading frames (ORFs) and a part of a third. Analysis of the deduced amino acid sequence of one of these ORFs, Q2/3L, revealed that this gene has the capacity to encode a protein which is related to members of the G-protein coupled chemokine receptor subfamily, the swinepoxvirus K2R and the human cytomegalovirus US28 ORFs. It has the key structural characteristics of the G-protein-coupled receptor superfamily, e.g., seven hydrophobic regions, predicted to span the cell membrane, and the cysteine residues in the first and second extracellular loops that are implicated in formation of a disulfide bond. Southern blot analysis showed that all three species of the Capripoxvirus genus, i.e., sheep pox, goat pox, and lumpy skin disease of cattle, contain copies of this putative G-proteincoupled chemokine receptor homologue

Nuclear Symmetry Energy: constraints from Giant Quadrupole Resonances and Parity Violating Electron Scattering

Experimental and theoretical efforts are being devoted to the study of observables that can shed light on the properties of the nuclear symmetry energy. We present our new results on the excitation energy [X. Roca-Maza et al., Phys. Rev. C 87, 034301 (2013)] and polarizability of the Isovector Giant Quadrupole Resonance (IVGQR), which has been the object of new experimental investigation [S. S. Henshaw et al., Phys. Rev. Lett. 107, 222501 (2011)]. We also present our theoretical analysis on the parity violating asymmetry at the kinematics of the Lead Radius Experiment [S. Abrahamyan et al. (PREx Collaboration), Phys. Rev. Lett. 108, 112502 (2012)] and highlight its relation with the density dependence of the symmetry energy [X. Roca-Maza et al., Phys. Rev. Lett. 106, 252501 (2011)].Comment: Proceedings - International Nuclear Physics Conference (INPC), Firenze 2 - 7 June 201

Competing Ground States in Triple-layered Sr4Ru3O10: Verging on Itinerant Ferromagnetism with Critical Fluctuations

Sr4Ru3O10 is characterized by a sharp metamagnetic transition and ferromagnetic behavior occurring within the basal plane and along the c-axis, respectively. Resistivity at magnetic field, B, exhibits low-frequency quantum oscillations when B||c-axis and large magnetoresistivity accompanied by critical fluctuations driven by the metamagnetism when B^c-axis. The complex behavior evidenced in resistivity, magnetization and specific heat presented is not characteristic of any obvious ground states, and points to an exotic state that shows a delicate balance between fluctuations and order.Comment: 18 pages, 4 figure

Observation of orbital ordering and origin of the nematic order in FeSe

To elucidate the origin of nematic order in FeSe, we performed field-dependent 77Se-NMR measurements on single crystals of FeSe. We observed orbital ordering from the splitting of the NMR spectra and Knight shift and a suppression of it with magnetic field B0 up to 16 T applied parallel to the Fe-planes. There is a significant change in the distribution and magnitude of the internal magnetic field across the orbital ordering temperature Torb while stripe-type antiferromagnetism is absent. Giant antiferromagnetic (AFM) spin fluctuations measured by the NMR spin-lattice relaxation are gradually developed starting at ~ 40 K, which is far below the nematic ordering temperature Tnem. These results demonstrate that orbital ordering is the origin of the nematic order, and the AFM spin fluctuation is the driving mechanism of superconductivity in FeSe under the presence of the nematic order.Comment: 6 pages, 4 figure