2,016 research outputs found
Unfolding the Sulcus
Sulci are localized furrows on the surface of soft materials that form by a
compression-induced instability. We unfold this instability by breaking its
natural scale and translation invariance, and compute a limiting bifurcation
diagram for sulcfication showing that it is a scale-free, sub-critical {\em
nonlinear} instability. In contrast with classical nucleation, sulcification is
{\em continuous}, occurs in purely elastic continua and is structurally stable
in the limit of vanishing surface energy. During loading, a sulcus nucleates at
a point with an upper critical strain and an essential singularity in the
linearized spectrum. On unloading, it quasi-statically shrinks to a point with
a lower critical strain, explained by breaking of scale symmetry. At
intermediate strains the system is linearly stable but nonlinearly unstable
with {\em no} energy barrier. Simple experiments confirm the existence of these
two critical strains.Comment: Main text with supporting appendix. Revised to agree with published
version. New result in the Supplementary Informatio
Excitable Patterns in Active Nematics
We analyze a model of mutually-propelled filaments suspended in a
two-dimensional solvent. The system undergoes a mean-field isotropic-nematic
transition for large enough filament concentrations and the nematic order
parameter is allowed to vary in space and time. We show that the interplay
between non-uniform nematic order, activity and flow results in spatially
modulated relaxation oscillations, similar to those seen in excitable media. In
this regime the dynamics consists of nearly stationary periods separated by
"bursts" of activity in which the system is elastically distorted and solvent
is pumped throughout. At even higher activity the dynamics becomes chaotic.Comment: 4 pages, 4 figure
Low-Temperature Spin Dynamics of Doped Manganites: roles of Mn-t2g and eg and O-2p states
The low-temperature spin dynamics of doped manganites have been analyzed
within a tight-binding model, the parameters of which are estimated by mapping
the results of ab initio density functional calculations onto the model. This
approach is found to provide a good description of the spin dynamics of the
doped manganites, observed earlier within the ab initio calculations. Our
analysis not only provides some insight into the roles of the eg and the t2g
states but also indicates that the oxygen p states play an important role in
the spin dynamics. This may cast doubt on the adaptability of the conventional
model Hamiltonian approaches to the analysis of spin dynamics of doped
manganites.Comment: 12 pages; Includes 5 figure
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
Bay of Bengal: From monsoons to mixing
The Bay of Bengal has a surprisingly large influence on the world. It nurtures the South Asian summer monsoon, a tremendous ocean-atmosphere-land phenomenon that delivers freshwater to more than a third of the human population
on this planet. During summer, southwesterly winds gather moisture from the ocean and carry it deep inland over the
Indian subcontinent, bringing welcome rains to a parched land. During winter, the winds reverse to northeasterly, and
the ocean circulation responds by dispersing the terrestrial freshwater run off concentrated in the northern part of the
bay
First Light of Engineered Diffusers at the Nordic Optical Telescope Reveal Time Variability in the Optical Eclipse Depth of WASP-12b
We present the characterization of two engineered diffusers mounted on the
2.5 meter Nordic Optical Telescope, located at Roque de Los Muchachos, Spain.
To assess the reliability and the efficiency of the diffusers, we carried out
several test observations of two photometric standard stars, along with
observations of one primary transit observation of TrES-3b in the red (R-band),
one of CoRoT-1b in the blue (B-band), and three secondary eclipses of WASP-12b
in V-band. The achieved photometric precision is in all cases within the
sub-millimagnitude level for exposures between 25 and 180 seconds. Along a
detailed analysis of the functionality of the diffusers, we add a new transit
depth measurement in the blue (B-band) to the already observed transmission
spectrum of CoRoT-1b, disfavouring a Rayleigh slope. We also report variability
of the eclipse depth of WASP-12b in the V-band. For the WASP-12b secondary
eclipses, we observe a secondary-depth deviation of about 5-sigma, and a
difference of 6-sigma and 2.5-sigma when compared to the values reported by
other authors in similar wavelength range determined from Hubble Space
Telescope data. We further speculate about the potential physical processes or
causes responsible for this observed variabilityComment: 11 pages, 9 figure
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.
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
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