3,359 research outputs found
Nondegenerate two-photon lasing in a single quantum dot
We propose two-mode two-photon microlaser using a single semiconductor
quantum dot grown inside a two-mode microcavity. We explore both incoherent and
coherent pumping at low temperatures to achieve suitable conditions for
two-mode two-photon lasing. The two-mode two-photon stimulated emission is
strongly suppressed but the single-photon stimulated emission is enhanced by
exciton-phonon interactions. In coherently pumped quantum dot one can achieve
large two-mode two-photon lasing where single-photon lasing is almost absent.
We also discuss generation of steady state two-mode entangled state using
two-photon resonant pumping.Comment: 12 pages, 13 figure
Self-induced Transparency in a Semiconductor Quantum Dot medium at ultra-cold temperatures
We investigate the feasibility of minimum absorption and minimum broadening
of pulse propagation in an inhomogeneously broadened semiconductor quantum dot
medium. The phonon interaction is inevitable in studying any semiconductor
quantum dot system. We have used the polaron transformation technique to deal
with quantum dot phonon interaction in solving system dynamics. We demonstrate
that a short pulse can propagate inside the medium with minimal absorption and
broadening in pulse shape. The stable pulse area becomes slightly higher than
the prediction of the pulse area theorem and is also dependent on the
environment temperature. The change in the final pulse shape is explained very
well by numerically solving the propagation equation supported by the
susceptibility of the medium. Our system also exhibits the pulse breakup
phenomena for higher input pulse areas. Therefore, the considered scheme can
have important applications in quantum communication, quantum information, and
mode-locking with the advantage of scalability and controllability.Comment: 11 pages, 11 figure
Design of Peptides With, α,β-Dehydro-Residues: A Dipeptide With a Branched β-Carbon Dehydro-Residue at the (\u3ci\u3ei\u3c/i\u3e+1) Position, Methyl \u3ci\u3eN\u3c/i\u3e-(benzyloxycarbonyl)-α,β-Didehydrovalyl-L-Tryptophanate
The structure of the title peptide, C25H27N3O5, has been determined and its conformation analysed. Values of the standard peptide torsion angles are φ(1) = -44.2 (3)°, ψ(1) = 135.9 (2)°, φ(2) = -141.6 (2)° and ψ(T/2) = 168.0 (2)°. The crystal structure is stabilized by an intermolecular hydrogen bond, with an N···O distance of 2.919 (3)Å, which is formed between screw-axis-related NH and CO groups of dehydrovaline residues
Intergranular Corrosion of Deformed SS304
Intergranuular corrosion (IGC) and intergranular stress corrosion cracking (IGSCC) of commercial stainless steels e.g. type 304 and 316 are frequently observed in several
process environments. These localized attacks are normally attributed to the carbide precipitation and concomitant depletion of chromium near grain boundary due to alloy
exposure to sensitization temperature. Such undesirable microchemistry is expected to be changed further if the material undergoes deformation prior to sensitization
119Sn NMR probe of magnetic fluctuations in SnO2 nanoparticles
119Sn nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation
rate (1/T1) in SnO2 nanoparticles were measured as a function of temperature
and compared with those of SnO2 bulk sample. A 15% loss of 119Sn NMR signal
intensity for the nano sample compared to the bulk sample was observed. This is
indicative of ferromagnetism from a small fraction of the sample. Another major
finding is that the recovery of the 119Sn longitudinal nuclear magnetization in
the nano sample follows a stretched exponential behavior, as opposed to that in
bulk which is exponential. Further, the 119Sn 1/T1 at room temperature is found
to be much higher for the nano sample than for its bulk counterpart. These
results indicate the presence of magnetic fluctuations in SnO2 nanoparticles in
contrast to the bulk (non-nano) which is diamagnetic. These local moments could
arise from surface defects in the nanoparticles.Comment: 5 pages, 6 figures, to appear in EPL 201
Antenatally diagnosed congenital anomalies-trend in tertiary care hospital
Background: Antenatally diagnosed, congenital abnormalities of the fetus are frequently offered antenatal surgical consultation in all tertiary care hospitals to adequately counsel prospective parents. We aimed to assess the current trends in antenatally diagnosed congenital malformations of fetus in patients who had presented to our hospital for reassessment or surgical consultation and these patients were counselled and prognosticated after confirmation of anomaly at our centre accordingly.Methods: This was a retrospective study of all the cases diagnosed antenatally with fetal abnormalities. All cases were referred to either pediatric surgery outpatient department or fetal medicine subunit of a tertiary care centre from January 2017-December 2018. The complete records of these pregnant women were perused, presence and type of anomaly confirmed at our centre and trends about types of anomalies analysed.Results: A total of 209 women were analyzed for antenatal anomalies, out of these patients medical termination of pregnancy was offered to 27 (12.9%) patients, in which 38 anomalies were detected and in 182 (87%) patients pregnancy was continued to delivery. A total of 223 anomalies were detected in this group with some patients having fetuses with more than one anomaly. Gastrointestinal abnormalities were present in 94 (51.6%) patients of those who delivered and accounted for the most common anomaly followed by CNS abnormality which accounted for 39 (21.4%) of total abnormalities and genitourinary abnormalities contributed to 28 (13.3%) of abnormalities. A total of 85.2% of patients were referred after 20 weeks.Conclusions: The significant number of patients with major congenital anomalies are still diagnosed at a date later than permissible time for termination of gestation (20 weeks). There were cases where anomaly scan was done at a later gestation and then there were others where inadequate counselling made patient to present late for prognostication. However, there are certain anomalies that are picked up late and are likely to be missed in the routine anomaly scan. Therefore, antenatal detection and early referral helps in offering early counselling and better outcome for pregnancy.
On the recent cyclone and tidal waves lashed along the coast of Midnapur district. West Bengal
strong cyclonic wind lashed along the southern
part of Midnapur district, West Bengal for three days
during 20th to 22nd August, 1997. The excessive tidal
waves caused by the cyclone was so mighty that extensive
interior areas were inundated resulting in heavy
loss to marine flsheiy sector. The landing centres
badly affected were Digha, Digha Mohana, Paramanighat
and Janasahi Jatmati
Chemically deposited magnesium hydroxide thin film
Here we report for the first time to the best of our knowledge the processing techniques, nucleation kinetics and the nanoindentation behaviour of a 1.5 mu m magnesium hydroxide thin film chemically deposited on a commercially available soda lime silica glass substrate at room temperature. The phase and microstructure of the films were analysed by X-ray diffraction, scanning electron microscopy, field emission scanning electron microscopy as well as transmission electron microscopy. An exponential nucleation kinetics was identified for the growth of the thin films. The nanomechanical properties, e. g. nanohardness and Young's modulus of the films were measured by the nanoindentation technique at ultralow loads of 50, 70 and 100 mu N. Finally, the nature of deformation of the thin film was analysed in terms of the energetics of the nanoindentation process and the microstructure
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