Tetramer Orbital-Ordering induced Lattice-Chirality in Ferrimagnetic, Polar MnTi2O4

Using density-functional theory calculations and experimental investigations on structural, magnetic and dielectric properties, we have elucidated a unique tetragonal ground state for MnTi2O4, a Ti^{3+} (3d^1)-ion containing spinel-oxide. With lowering of temperature around 164 K, cubic MnTi2O4 undergoes a structural transition into a polar P4_1 tetragonal structure and at further lower temperatures, around 45 K, the system undergoes a paramagnetic to ferrimagnetic transition. Magnetic superexchange interactions involving Mn and Ti spins and minimization of strain energy associated with co-operative Jahn-Teller distortions plays a critical role in stabilization of the unique tetramer-orbital ordered ground state which further gives rise to lattice chirality through subtle Ti-Ti bond-length modulations

Self-Energy Effects on the Low- to High-Energy Electronic Structure of SrVO3

The correlated electronic structure of SrVO3 has been investigated by angle-resolved photoemission spectroscopy using in-situ prepared thin films. Pronounced features of band renormalization have been observed: a sharp kink ~60 meV below the Fermi level (EF) and a broad so-called "high-energy kink" ~0.3 eV below EF as in the high-Tc cuprates although SrVO3 does not show magnetic fluctuations. We have deduced the self-energy in a wide energy range by applying the Kramers-Kronig relation to the observed spectra. The obtained self-energy clearly shows a large energy scale of ~0.7 eV which is attributed to electron-electron interaction and gives rise to the ~0.3 eV "kink" in the band dispersion as well as the incoherent peak ~1.5eV below EF. The present analysis enables us to obtain consistent picture both for the incoherent spectra and the band renormalization.Comment: 5 pages, 3 figure

Observational Signature of Tidal Disruption of a Star by a Massive Black Hole

We have modeled the time-variable profiles of the Halpha emission line from the non-axisymmetric disk and debris tail created in the tidal disruption of a solar-type star by a million solar mass black hole. We find that the line profiles at these very early stages of the evolution of the post-disruption debris do not resemble the double peaked profiles expected from a rotating disk since the debris has not yet settled into such a stable structure. The predicted line profiles vary on fairly short time scales (of order hours to days). As a result of the uneven distribution of the debris and the existence of a ``tidal tail'' (the stream of returning debris), the line profiles depend sensitively on the orientation of the tail relative to the line of sight. Given the illuminating UV/X-ray light curve, we also model the Halpha light curve from the debris.Comment: 2 pages, 1 figure, to appear in the proceedings of "The Interplay among Black Holes, Stars and ISM in Galactic Nuclei", IAU 222, eds. Th. Storchi Bergmann, L.C. Ho, and H.R. Schmit

SYNTHESIS, IN VITRO ANTIBACTERIAL, TOXICITY AND MOLECULAR DOCKING ANTICANCER ACTIVITY OF NOVEL N-[(2-CHLOROQUINOLIN-3-YL) METHYLIDENE]-2-ANILINE SCHIFF'S BASES

Objective: Synthesis of N-[(2-chloroquinolin-3-yl) methylidene]-2-aniline schiff bases (3a-j) and to study their in vitro antibacterial activity and in silico study towards cancer and malarial proteins. Methods: Various N-[(2-chloroquinolin-3-yl) methylidene]-2-aniline schiff bases (3a-j) were synthesized by using 2-chloro-3-formyl quinoline and different anilines in presence of acetic acid as catalyst. All the new compounds were characterized by 1H-NMR, [13]C-NMR and LCMS analysis. The compounds 3a-j was subjected to antibacterial activity. In silico molecular properties were predicted using various online cheminformatic tools, the binding interactions with Human DNA topoisomerase I and Plasmodium falciparum lactate dehydrogenase proteins was studied through molecular docking and Irinotecan and mefloquine were used as reference drugs. Results: Fairly good yield of N-[(2-chloroquinolin-3-yl) methylidene]-2-aniline schiff bases (3a-j) were synthesized by convenient and economical procedure. The preliminary in silico pharmacokinetics study reveals that the compounds 3a-j shows excellent drug like property. The toxicity profile of compounds 3a-h was found safe. The compounds 3a-j was exhibited promising MIC values against the both S. aureus and E. coli. Similarly the docking results predict that the compound 3d shown highest interaction by forming two hydrogen bonds against the cancer protein with the interaction energy-20.696 kcal/mol. Compound 3c exhibits highest dock score of-45.703 kcal/mol with two hydrogen bonds against malarial protein. Conclusion: From the results of docking studies of N-[(2-chloroquinolin-3-yl) methylidene]-2-aniline schiff bases (3a-j), it has been concluded that the compounds were found to exhibit multifunctional lead property, hence these compounds are worth to be considered as potential lead molecules for further study

SYNTHESIS AND MOLECULAR DOCKING STUDY OF 2-ARYL/HETEROARYL-6-CHLOROQUINOLINE-4-CARBOXYLIC ACIDS WITH PLASMODIUM LDH RECEPTOR PROTEIN

Objective: Synthesis and in silico molecular docking studies of 2-aryl/heteroaryl-quinoline-4-carboxylic acid derivatives (3a-j) with plasmodium LDH receptor protein.Methods: The 2-aryl/heteroaryl-quinoline-4-carboxylic acids (3a-j) were obtained by Pfitzinger reaction. Ligands (3a-j) interaction with plasmodium LDH receptor protein was studied through molecular docking method.Results: Good yields of 2-aryl/heteroaryl-quinoline-4-carboxylic acid derivatives (3a-j) were obtained by convenient and economical procedure. Their structures were confirmed by 1H NMR, 13C NMR, and MS spectral analysis. The binding site analysis of the synthesized compounds (3a-j) with plasmodium LDH receptor that are responsible for malaria parasite response was evaluated through molecular docking study. The results reveal that the ligand 3d shows maximum of five hydrogen bonding interactions with binding energy -9.05 kcal/mol, shown to be a promising lead molecule to inhibit Plasmodium LDH receptor.Conclusion: The docking studies of newly synthesized 2-aryl/heteroaryl-quinoline-4-carboxylic acids were found to be very useful ligands for antimalarial therapy particularly on Plasmodium LDH protein. However the installation of still many appropriate substitutions on quinoline moiety would lead to identification of novel antimalarial compounds that ascertained via molecular docking is underway in our lab

Electromigration-Induced Propagation of Nonlinear Surface Waves

Due to the effects of surface electromigration, waves can propagate over the free surface of a current-carrying metallic or semiconducting film of thickness h_0. In this paper, waves of finite amplitude, and slow modulations of these waves, are studied. Periodic wave trains of finite amplitude are found, as well as their dispersion relation. If the film material is isotropic, a wave train with wavelength lambda is unstable if lambda/h_0 < 3.9027..., and is otherwise marginally stable. The equation of motion for slow modulations of a finite amplitude, periodic wave train is shown to be the nonlinear Schrodinger equation. As a result, envelope solitons can travel over the film's surface.Comment: 13 pages, 2 figures. To appear in Phys. Rev.

Origin of G-type Antiferromagnetism and Orbital-Spin Structures in LaTiO3{\rm LaTiO}_3

The possibility of the $D_{3d}$ distortion of ${\rm TiO}_6$ octahedra is examined theoretically in order to understand the origin of the G-type antiferromagnetism (AFM(G)) and experimentally observed puzzling properties of ${\rm LaTiO}_3$. By utilizing an effective spin and pseudospin Hamiltonian with the strong Coulomb repulsion, it is shown that AFM(G) state is stabilized through the lift of the $t_{2g}$-orbital degeneracy accompanied by a tiny $D_{3d}$-distortion . The estimated spin-exchange interaction is in agreement with that obtained by the neutron scattering. Moreover, the level-splitting energy due to the distortion can be considerably larger than the spin-orbit interaction even when the distortion becomes smaller than the detectable limit under the available experimental resolution. This suggests that the orbital momentum is fully quenched and the relativistic spin-orbit interaction is not effective in this system, in agreement with recent neutron-scattering experiment.Comment: 9 pages, 6 figure

Fingerprints of Spin-Orbital Physics in Crystalline O2_2

The alkali hyperoxide KO$_2$ is a molecular analog of strongly-correlated systems, comprising of orbitally degenerate magnetic O$_2^-$ ions. Using first-principles electronic structure calculations, we set up an effective spin-orbital model for the low-energy \textit{molecular} orbitals and argue that many anomalous properties of KO$_2$ replicate the status of its orbital system in various temperature regimes.Comment: 4 pages, 2 figures, 1 tabl

Microscopic origin of diagonal stripe phases in doped nickelates

We investigate the electron density distribution and the stability of stripe phases in the realistic two-band model with hopping elements between e_g orbitals at Ni sites on the square lattice, and compare these results with those obtained for the doubly degenerate Hubbard model with two equivalent orbitals and diagonal hopping. For both models we determine the stability regions of filled and half-filled stripe phases for increasing hole doping x=2-n in the range of x<0.4, using Hartree-Fock approximation for large clusters. In the parameter range relevant to the nickelates, we obtain the most stable diagonal stripe structures with filling of nearly one hole per atom, as observed experimentally. In contrast, for the doubly degenerate Hubbard model the most stable stripes are somewhat reminiscent of the cuprates, with half-filled atoms at the domain wall sites. This difference elucidates the crucial role of the off-diagonal e_g hopping terms for the stripe formation in La_2-xSr_xNiO_4. The influence of crystal field is discussed as well.Comment: 15 pages, 12 figure

Bias reduction in traceroute sampling: towards a more accurate map of the Internet

Traceroute sampling is an important technique in exploring the internet router graph and the autonomous system graph. Although it is one of the primary techniques used in calculating statistics about the internet, it can introduce bias that corrupts these estimates. This paper reports on a theoretical and experimental investigation of a new technique to reduce the bias of traceroute sampling when estimating the degree distribution. We develop a new estimator for the degree of a node in a traceroute-sampled graph; validate the estimator theoretically in Erdos-Renyi graphs and, through computer experiments, for a wider range of graphs; and apply it to produce a new picture of the degree distribution of the autonomous system graph.Comment: 12 pages, 3 figure