Size-dependent linear and non-linear optical response of single carrier two-dimensional quantum dots

We explore the pattern of size dependence of linear and non-linear optical (NLO) responses of one-electron quantum dots in two dimensions with or without anharmonicity in the confinement potential. For some fixed values of transverse magnetic field strength (ω_c) and harmonic confinement potential (ω₀), the influence of the size of the dot on the linear (), the first (β) and the second (γ) NLO responses of the system computed through a finite field linear variational route is analysed. Size-dependent maximization is predicted to be feasible for the quadratic hyperpolarizability.     

Seasonal variation of daily total column ozone (TCO) and role of its depletion and formation rate on surface temperature over Dumdum at Kolkata, India

The purpose of the paper is to present the variation of total ozone concentration over Dumdum at Kolkata, India during different seasons. It is concluded that the trend of ozone concentration during different seasons are different. A critical analysis is done and following important results are obtained.

X-ray photoelectron spectroscopy studies on core-shell structured nanocomposites

Core-shell nanostructures were grown in silica-based glasses. Copper-copper oxide and iron-iron oxide structures had diameters in the range 3-6 nm, with shell thicknesses ∼1-2 nm. Silver-lithium niobate core-shell nanostructures had diameters in the range 4.2-46 nm and thicknesses varying from 2.2 to 22 nm. X-ray photoelectron spectroscopy studies were carried out on all these specimens. The analyses of these results show the presence of Cu⁺/Cu²⁺, Fe²⁺/Fe³⁺ and Nb⁴⁺/Nb⁵⁺ valence states in the above three systems. Electrical resistivity data were fitted satisfactorily to the small polaron hopping model in the case of copper and iron-containing specimens. The presence of ions in the lithium niobate shell provides direct evidence of the formation of localized states between which variable range hopping conduction can be effected.     

A novel “magnetic” field and its dual non-commutative phase space

In this Letter we have studied a new form of non-commutative (NC) phase space with an operatorial form of noncommutativity. A point particle in this space feels the effect of an interaction with an “internal  ” magnetic field, that is singular at a specific position θ⁻¹${\theta }^{\mathrm{-1}}$. By “internal” we mean that the effective magnetic fields depends essentially on the particle properties and modifies the symplectic structure. Here θ is the NC parameter and induces the coupling between the particle and the “internal” magnetic field. The magnetic moment of the particle is computed. Interaction with an external physical magnetic field reveals interesting features induced by the inherent fuzziness of the NC phase space: introduction of non-trivial structures into the charge and mass of the particle and possibility of the particle dynamics collapsing to a Hall type of motion. The dynamics is studied both from Lagrangian and symplectic (Hamiltonian) points of view. The canonical (Darboux) variables are also identified. We briefly comment, that the model presented here, can play interesting role in the context of (recently observed) real space Berry curvature in material systems.     

Synthesis of SnS thin films via galvanostatic electrodeposition and fabrication of CdS/SnS heterostructure for photovoltaic applications

In this work SnS thin films were electrochemically deposited on ITO coated glass substrate by galvanostatic electrodeposition at different pH of the plating bath. The working electrode used in these studies was low cost high purity graphite rod. The as-deposited films were found to be smooth, pinhole free and well adherent to the substrate with no powdery deposition. EDX measurements revealed that all the SnS films were non-stoichiometric in nature with variation from Sn-excess to S-excess compositions. XRD pattern showed that all the SnS thin films had orthorhombic polycrystalline structure. The direct bandgaps of all the films were found to be in the range 1.54-1.58 eV. ITO/SnS/In structure exhibited linear current-voltage characteristics, establishing the ohmic nature of both ITO/SnS and SnS/In junctions. Furthermore, SnS layer was grown on CdS film using electrodeposition technique. The heterostructure ITO/CdS/SnS/In was characterized under dark and illuminated conditions. From forward biased I-V characteristics several junction parameters like barrier height, diode ideality factor and series resistance of the heterostructure were extracted using Cheung model.     

A novel frequency encoded all optical CNOT gate exploiting difference frequency generation and implementation of fast binary adders using frequency encoding and nonlinear dielectric films

Optics has an important role in logic implementation and computation is established in two and half decades by many researchers. Recently frequency encoding technique is established. This technique does not suffer from intensity dependent loss problems like other schemes. Amorphous dielectric thin films with reflecting edges can also be used for logic realization and has very fast response speed. It also does not use any semiconductor device and simple to construct. In this communication the authors have proposed all optical CNOT gate using frequency encoded difference frequency generation exploiting nonlinear response of some material and implementation of binary adders by CNOT gate and dielectric thin film AND gate.     

He(I) and He(II) populations in the Nagoya TPD plasma machine

A collisional-radiative model is used to explain the He(I) population densities observed by Otsuka, Ikee and Ishii in their TPD plasma machine. It is shown that a plasma model, which is partially optically thick to He(II) Lyman radiation, can explain the experimentally observed He(II) population density at T_e=3.17 eV. The agreement between the experimental and calculated He(II) population densities observed by Otsuka and others is shown to be due to an error in their calculations.     

PHOTOREACTIVATION OF THYMINE-STARVED ESCHERICHIA COLIBs-1

Abstract —Thymine starvation prior to 254 nm ultraviolet light (UV) exposures has been found to decrease the level of maximum photoreactivation in Escherichia coli B _s-1. The dark equilibrium level of photoreactivating enzyme-substrate complexes was determined from the levels of photoreactivation obtained with exposures to single flashes of high-intensity light. The kinetics indicate that photoreactivating enzyme concentration does not decrease as a result of thymine starvation. The UV sensitivities of normal and thymine-starved cells are found to be the same. Photoreactivation by sequential flashes shows a lesser number of total photorepairable lesions in starved cells. It is concluded that thymine starvation renders a portion of the dimers inaccessible to the photoreactivating enzyme, thus lowering the level of maximum photoreactivation.     

Über die Eigenschaften hydratisierten Chromoxydes. Teil V

Ohne ZusammenfassungÜbersetzt von Dr. K. Jäckel, Marburg/L.Wir danken Herrn Prof. N. R. Dhar D.Sc. (London und Paris), F.R.I.C., F.N.I., I.E.S. (Eetd) Direktor Shila Dhar Institut für Bodenkunde und Vorstand der Chemischen Abteilung, Universität Allahabad, für sein lebhaftes Interesse und seine Ratschläge für die Arbeit.