958 research outputs found
Enhanced Raman and photoluminescence response in monolayer MoS due to laser healing of defects
Bound quasiparticles, negatively charged trions and neutral excitons, are
associated with the direct optical transitions at the K-points of the Brillouin
zone for monolayer MoS. The change in the carrier concentration,
surrounding dielectric constant and defect concentration can modulate the
photoluminescence and Raman spectra. Here we show that exposing the monolayer
MoS in air to a modest laser intensity for a brief period of time enhances
simultaneously the photoluminescence (PL) intensity associated with both trions
and excitons, together with 3 to 5 times increase of the Raman intensity
of first and second order modes. The simultaneous increase of PL from trions
and excitons cannot be understood based only on known-scenario of depletion of
electron concentration in MoS by adsorption of O and HO molecules.
This is explained by laser induced healing of defect states resulting in
reduction of non-radiative Auger processes. This laser healing is corroborated
by an observed increase of intensity of both the first order and second order
2LA(M) Raman modes by a factor of 3 to 5. The A mode hardens by
1.4 cm whereas the E mode softens by 1 cm.
The second order 2LA(M) Raman mode at 440 cm shows an increase in
wavenumber by 8 cm with laser exposure. These changes are a
combined effect of change in electron concentrations and oxygen-induced lattice
displacements.Comment: 15 pages, 5 figures, Journal of Raman Spectroscopy, 201
Nanoparticle-coated microcrystals
Coprecipitation provides a rapid high-yield method for self-assembly of nanoparticles on the surface of flat water-soluble crystalline surfaces and a simple immobilisation technique prior to storage or thermal and chemical modification
An impact of age, birth order and qualification on women in sports participation levels in Tamilnadu and Pondicherry
The position, a child had by the order of birth significantly affected the child’s growth and personality. Research in the late twentieth century and early twenty-first century shows even greater influence, contributing to intelligence, career choice, and to a certain degree, success in adulthood. Until the independence of India, The present research is to examine whether the age, order of birth and qualification of women have any impact on women's participation in sports among Tamil Nadu and Pondicherry at different levels. Sixty women players were randomly selected from 4 Colleges of two different states. First half from Cuddalore, Tamil Nadu state and second half from Karaikal, Pondicherry state. The selected subjects were with a brief questionnaire, to find out their level of sports participation, age, order of birth and qualification. Data obtained were subjected to find out statistical significance among the means using 3 (levels - district, state and national participations) x 2 (states -Tamil Nadu and Pondicherry) Factorial analysis. The results proved that there were significant differences in age and qualifications of the different level of women players. There was no significant difference among the states, Tamil Nadu and Pondicherry in age, order of birth and qualifications of the women players. It was concluded that age and qualification play vital role in the participation level of women players
Phonon Anomalies, Orbital-Ordering and Electronic Raman Scattering in iron-pnictide Ca(Fe0.97Co0.03)2As2: Temperature-dependent Raman Study
We report inelastic light scattering studies on Ca(Fe0.97Co0.03)2As2 in a
wide spectral range of 120-5200 cm-1 from 5K to 300K, covering the tetragonal
to orthorhombic structural transition as well as magnetic transition at Tsm ~
160K. The mode frequencies of two first-order Raman modes B1g and Eg, both
involving displacement of Fe atoms, show sharp increase below Tsm.
Concomitantly, the linewidths of all the first-order Raman modes show anomalous
broadening below Tsm, attributed to strong spin-phonon coupling. The high
frequency modes observed between 400-1200 cm-1 are attributed to the electronic
Raman scattering involving the crystal field levels of d-orbitals of Fe2+. The
splitting between xz and yz d-orbital levels is shown to be ~ 25 meV which
increases as temperature decreases below Tsm. A broad Raman band observed at ~
3200 cm-1 is assigned to two-magnon excitation of the itinerant Fe 3d
antiferromagnet.Comment: Accepted for Publication in JPC
An evaluvation of the self-esteem of women sports participant in various games
The present study was conducted in Tamil Nadu state, India with the objective of studying self-esteem of women sports participant in different games. Exploratory research design was adopted for the study. The total sample comprised of 90 playing women in which 30 were Kho - Kho / Kabaddi players, 30 were Badminton / Ball Badminton / Volley Ball players and 30 were Squash Rackets / Table Tennis / Fencing / Tennis players. Self esteem scale developed by Verma and Kapadia was used to collect the data. The investigators personally met the respondents by going to their place and administered the tests and collected the data. Among all the three categories of women sports participants, the Squash Rackets / Table Tennis / Fencing / Tennis were having high level of self esteem followed by Badminton / Ball Badminton and Kho - Kho / Kabaddi players. Collectively as one group, most of them were having high and medium level of self esteem reflecting that sports performance of women promotes esteem of women. Through correlation it was found that education and playing experience were significantly and positively related to self esteem of women sports participants. Hence women with higher education and higher playing experience had higher self esteem
Cannabinoid-Mediated Inhibition of Recurrent Excitatory Circuitry in the Dentate Gyrus in a Mouse Model of Temporal Lobe Epilepsy
Temporal lobe epilepsy (TLE) is a neurological condition associated with neuron loss, axon sprouting, and hippocampal sclerosis, which results in modified synaptic circuitry. Cannabinoids appear to be anti-convulsive in patients and animal models of TLE, but the mechanisms of this effect are not known. A pilocarpine-induced status epilepticus mouse model of TLE was used to study the effect of cannabinoid agonists on recurrent excitatory circuits of the dentate gyrus using electrophysiological recordings in hippocampal slices isolated from control mice and mice with TLE. Cannabinoid agonists WIN 55,212-2, anandamide (AEA), or 2-arachydonoylglycerol (2-AG) reduced the frequency of spontaneous and tetrodotoxin-resistant excitatory postsynaptic currents (EPSCs) in mice with TLE, but not in controls. WIN 55,212-2 also reduced the frequency of EPSCs evoked by glutamate-photolysis activation of other granule cells in epileptic mice. Secondary population discharges evoked after antidromic electrical stimulation of mossy fibers in the hilus were also attenuated by cannabinoid agonists. Agonist effects were blocked by the cannabinoid type 1 receptor (CB1R) antagonist AM251. No change in glutamate release was observed in slices from mice that did not undergo status epilepticus. Western blot analysis suggested an up-regulation of CB1R in the dentate gyrus of animals with TLE. These findings indicate that activation of CB1R present on nerve terminals can suppress recurrent excitation in the dentate gyrus of mice with TLE. This suggests a mechanism for the anti-convulsive role of cannabinoids aimed at modulating receptors on synaptic terminals expressed de novo after epileptogenesis
Metallic monoclinic phase in VO induced by electrochemical gating: in-situ Raman study
We report in-situ Raman scattering studies of electrochemically top gated
VO thin film to address metal-insulator transition (MIT) under gating. The
room temperature monoclinic insulating phase goes to metallic state at a gate
voltage of 2.6 V. However, the number of Raman modes do not change with
electrolyte gating showing that the metallic phase is still monoclinic. The
high frequency Raman mode A(7) near 616 cm ascribed to V-O vibration
of bond length 2.06 \AA~ in VO octahedra hardens with increasing gate
voltage and the B(3) mode near 654 cm softens. This shows that the
distortion of the VO octahedra in the monoclinic phase decreases with
gating. The time dependent Raman data at fixed gate voltages of 1 V (for 50
minute, showing enhancement of conductivity by a factor of 50) and 2 V (for 130
minute, showing further increase in conductivity by a factor of 5) show similar
changes in high frequency Raman modes A(7) and B(3) as observed in
gating. This slow change in conductance together with Raman frequency changes
show that the governing mechanism for metalization is more likely to the
diffusion controlled oxygen vacancy formation due to the applied electric
field.Comment: 5 pages, 6 figure
Symmetry-dependent phonon renormalization in monolayer MoS2 transistor
Strong electron-phonon interaction which limits electronic mobility of
semiconductors can also have significant effects on phonon frequencies. The
latter is the key to the use of Raman spectroscopy for nondestructive
characterization of doping in graphene-based devices. Using in-situ Raman
scattering from single layer MoS electrochemically top-gated field effect
transistor (FET), we show softening and broadening of A phonon with
electron doping whereas the other Raman active E mode remains
essentially inert. Confirming these results with first-principles density
functional theory based calculations, we use group theoretical arguments to
explain why A mode specifically exhibits a strong sensitivity to
electron doping. Our work opens up the use of Raman spectroscopy in probing the
level of doping in single layer MoS-based FETs, which have a high on-off
ratio and are of enormous technological significance.Comment: 5 pages, 3 figure
Sharp Raman Anomalies and Broken Adiabaticity at a Pressure Induced Transition from Band to Topological Insulator in Sb2Se3
The nontrivial electronic topology of a topological insulator is thus far
known to display signatures in a robust metallic state at the surface. Here, we
establish vibrational anomalies in Raman spectra of the bulk that signify
changes in electronic topology: an E2 g phonon softens unusually and its
linewidth exhibits an asymmetric peak at the pressure induced electronic
topological transition (ETT) in Sb2Se3 crystal. Our first-principles
calculations confirm the electronic transition from band to topological
insulating state with reversal of parity of electronic bands passing through a
metallic state at the ETT, but do not capture the phonon anomalies which
involve breakdown of adiabatic approximation due to strongly coupled dynamics
of phonons and electrons. Treating this within a four-band model of topological
insulators, we elucidate how nonadiabatic renormalization of phonons
constitutes readily measurable bulk signatures of an ETT, which will facilitate
efforts to develop topological insulators by modifying a band insulator
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