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