148 research outputs found
Emergence of a spin-liquid-like phase in quantum spin-ladder Ba2CuTeO6 with chemical substitution
Stabilization of the quantum spin liquids is vital to realize applications in
spintronics and quantum computing. The unique magnetic structure of Ba2CuTeO6
comprising of coupled spin-ladders with finite inter-ladder coupling brings the
system close to the quantum critical point. This opens up possibilities to
stabilize unconventional magnetic phases by tailoring the intra- and
inter-ladder exchange couplings. Here, we demonstrate a spin-liquid-like phase
in Ba2CuTeO6 using the method of chemical substitution. We choose non-magnetic
La3+ cation to substitute the Ba2+ in Ba2CuTeO6 and present signature
fingerprints such as deprived magnetic transition, non-dispersive AC
susceptibility, magnetic field-independent heat capacity, and broad Raman
continuum supporting the emergence of a spin-liquid-like phase. We believe that
an increased magnetic frustration and spin-fractionalization upon chemical
substitution play a crucial role in driving such a state. In addition,
temperature and magnetic field-dependent phonon response indicate the presence
of magnetostriction (spin-lattice coupling) in La-doped Ba2CuTeO6, a notable
property of spin-liquids
Tailoring the defects and electronic band structure in WS2/h-BN heterostructure
The 2D semiconducting transition metal dichalcogenides (e.g., WS2) host
strong coupling between various degrees of freedom leading to potential
applications in next-generation device applications including optoelectronics.
Such applications are strongly influenced by defects which can control both the
optical and electronic properties of the material. We demonstrate the
possibility to tailor the defect-related electronic states and the lattice
dynamics properties of WS2 in their heterostructures with h-BN which host a
strong interlayer coupling between the charge carriers in the WS2 layer and the
phonons of h-BN. This coupling is observed to induce modifications to the
interlayer phonons (manifested by their modified Raman-activity) and to the
charge carrier mobilities in the WS2 layer (which results in creation of
mid-gap energy states associated with many-body quasiparticle states). Our
study also includes a detailed characterization of the defects through Raman
measurements revealing an A_1g-type nature with differential resonance behavior
for the modes that are related to defect scattering with respect to the other
normal phonon modes of WS2.Comment: 22 pages, 5 figures, Supplemental materia
HYPOGLYCEMIC AND ANTIHYPERLIPIDEMIC EFFECTS OF ADIANTUM CAUDATUM IN ALLOXAN INDUCED DIABETES IN RATS
ABSTRACTObjective: To investigate the hypoglycemic and antihyperlipidemic effect of a successive ethanolic extract of Adiantum caudatum (EEAC) whole plantin alloxan induced diabetic rats.Methods: Diabetes was induced in Wistar albino rats by the administration of alloxan (140 mg/kg b. w., i.p.). EEAC (200 mg/kg b. w., p.o.) wasadministered to diabetic rats for 21 days in alloxan induced diabetic rats. The effect of EEAC on blood glucose and body weight was studied in alloxaninduced diabetic rats. All these effects were compared with glibenclamide (10 mg/kg b. w., p.o.) as a reference antidiabetic drug.Results: The administration of EEAC (200 mg/kg b. w., p.o.) resulted in a significant decrease in blood glucose level and a significant increase in bodyweight in alloxan induced diabetic rats. Furthermore, EEAC showed antihyperlipidemic activity as evidenced by a significant decrease in serum totalcholesterol and triglyceride levels in alloxan induced diabetic rats.Conclusion: The results suggest that the EEAC possess a promising hypoglycemic effect in alloxan induced diabetic rats.Keywords: Hypoglycemic, Antihyperlipidemic, Adiantum caudatum, Alloxan, Diabetes
Wrinkles, folds and ripplocations: unusual deformation structures of confined elastic sheets at non-zero temperatures
We study the deformation of a fluctuating crystalline sheet confined between
two flat rigid walls as a simple model for layered solids where bonds among
atoms {\it within} the same layer are much stronger than those {\it between}
layers. When subjected to sufficiently high loads in an appropriate geometry,
these solids deform and fail in unconventional ways. Recent experiments suggest
that configurations named {\it ripplocations}, where a layer folds backwards
over itself, are involved. These structures are distinct and separated by large
free energy barriers from smooth {\it ripples} of the atomic layers that are
always present at any non-zero temperature. We use Monte Carlo simulation in
combination with an umbrella sampling technique to obtain conditions under
which such structures form and study their specific experimental signatures.Comment: 8 pages, 7 figure
Manifestation of geometric frustration on magnetic and thermodynamic properties of pyrochlores (X=Ti, Zr)
We present here magnetization, specific heat and Raman studies on
single-crystalline specimens of the first pyrochlore member of
the rare-earth titanate series. Its analogous compound in the
rare-earth zirconate series is also investigated in the polycrystalline form.
The Sm spins in remain unordered down to at least T = 0.5 K. The
absence of magnetic ordering is attributed to very small values of exchange
() and dipolar interaction ()
between the spins in this pyrochlore. In contrast, the pyrochlore
is characterized by a relatively large value of Sm-Sm spin
exchange (); however, long-range ordering of the
spins is not established at least down to T = 0.67 K, due to
frustration of the spins on the pyrochlore lattice. The ground state
of ions in both pyrochlores is a well-isolated Kramer's doublet. The
higher-lying crystal field excitations are observed in the low-frequency region
of the Raman spectra of the two compounds recorded at T = 10 K. At higher
temperatures, the magnetic susceptibility of shows a broad
maximum at T = 140 K while that of changes monotonically. Whereas
is a promising candidate for investigating spin-fluctuations on a
frustrated lattice as indicated by our data, the properties of
seem to conform to a conventional scenario where geometrical frustration of the
spin exclude their long-range ordering.Comment: 24 pages, 6 figures, Accepted for publication in Phys. Rev.
Anomalous Raman scattering from phonons and electrons of superconducting FeSe
We report interesting anomalies in the temperature dependent Raman spectra of
FeSe measured from 3K to 300K in the spectral range from 60 to 1800
cm and determine their origin using complementary first-principles
density functional calculations. A phonon mode near 100 cm exhibits a
sharp increase by 5% in frequency below a temperature T ( 100
K) attributed to strong spin-phonon coupling and onset of short-range
antiferromagnetic order. In addition, two high frequency modes are observed at
1350 cm and 1600 cm, attributed to electronic Raman scattering
from ()to / -orbitals of Fe.Comment: 19 pages, 4 figures, 1 tabl
Evidence of Charge-Phonon coupling in Van der Waals materials Ni1-xZnxPS3
NiPS3 is a Van der Waals antiferromagnet that has been found to display
spin-charge and spin-phonon coupling in its antiferromagnetically ordered state
below TN = 155 K. Here, we study high-quality crystals of site-diluted
Ni1-xZnxPS3 (0 < x < 0.2) using temperature-dependent specific heat and Raman
spectroscopy probes. The site dilution suppresses the antiferromagnetic
ordering in accordance with the mean-field prediction. In NiPS3, we show that
the phonon mode P2 (176 cm-1) associated with Ni vibrations show a distinct
asymmetry due to the Fano resonance, which persists only in the paramagnetic
phase, disappearing below T_N = 155 K. This was further supported by
temperature-dependent Raman data on an 8% Zn-doped crystal (T_N = 135 K) where
Fano resonance similarly van in the magnetically ordered phase. This is
contrary to the behaviour of the Raman mode P9 (570 cm-1), which shows a Fano
resonance at low temperatures below T_N due to its coupling with the two-magnon
continuum. We show that the Fano resonance of P2 arises from its coupling with
an electronic continuum that weakens considerably upon cooling to low
temperatures. In the doped crystals, the Fano coupling is found to enhance with
Zn-doping. These observations suggest the presence of strong electron-phonon
coupling in the paramagnetic phase of NiPS3 due to charge density fluctuations
associated with the negative charge transfer state of Ni
An Investigation of Suicidal Ideation from Social Media Using Machine Learning Approach
Despite improvements in the detection and treatment of severe mental disorders, suicide remains a significant public health concern. Suicide prevention and control initiatives can benefit greatly from a thorough comprehension and foreseeability of suicide patterns. Understanding suicide patterns, especially through social media data analysis, can help in suicide prevention and control efforts. The objective of this study is to evaluate predictors of suicidal behavior in humans using machine learning. It is crucial to create a machine learning model for detection of suicide thoughts by monitoring a user's social media posts to identify warning signs of mental health issues. Through the analysis of social media posts, our research intends to develop a machine learning model for identifying suicide ideation and probable mental health problems. This study will help immensely to comprehend the environmental risk factors that influence suicidal thoughts and conduct across time. In this research the use of machine learning on social media data is an exciting new direction for understanding the environmental risk factors that impact an individual's susceptibility to suicide ideation and conduct over time. The machine learning algorithms showed high accuracy, precision, recall, and F1-score in detecting suicide patterns on social media data whereas SVM has the highest performance with an accuracy of 0.886.
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