Bistable behavior of a two-mode Bose-Einstein condensate in an optical cavity

We consider a two-component Bose-Einstein condensate in a one-dimensional optical cavity. Specifically, the condensate atoms are taken to be in two degenerate modes due to their internal hyperfine spin degrees of freedom and they are coupled to the cavity field and an external transverse laser field in a Raman scheme. A parallel laser is also exciting the cavity mode. When the pump laser is far detuned from its resonance atomic transition frequency, an effective nonlinear optical model of the cavity-condensate system is developed under Discrete Mode Approximation (DMA), while matter-field coupling has been considered beyond the Rotating Wave Approximation. By analytical and numerical solutions of the nonlinear dynamical equations, we examine the mean cavity field and population difference (magnetization) of the condensate modes. The stationary solutions of both the mean cavity field and normalized magnetization demonstrate bistable behavior under certain conditions for the laser pump intensity and matter-field coupling strength.Comment: Proceeding of Laser Physics 201

A Simple and Efficient Synthesis of 12-Aryl-8,9,10,12- tetrahydrobenzo[a]xanthen-11-ones by ZnO Nanoparticles Catalyzed Three Component Coupling Reaction of Aldehydes, 2-Naphthol and Dimedone

Highly effective zinc oxide nanoparticles catalyzed solvent-free synthesis of some tetrahydrobenzo[a]xanthen-11-one derivatives via one-pot multi-component reaction of aldehydes, 2-naphthol and dimedone. The present approach creates a variety of biologically active heterocyclic compounds in excellent yields and short reaction times. Four new compounds are reported. The salient features of the ZnO nanoparticles are: easy preparation, cost-effective, high stability, low loading and reusability of the catalyst. The prepared zinc oxide nanoparticles were fully characterized by EDX, XRD, SEM, IR and TEM analysis.KEYWORDS: ZnO, nanoparticles, tetrahydrobenzo[a]xanthen-11-one, multi-component reactions,  heterocyclic compounds

Investigation and modelling of traffic issues in immersive audio environments

Copyright © 2004 IEEEA growing area of technical importance is that of distributed virtual environments for work and play. For the audio component of such environments to be useful, great emphasis must be placed on the delivery of high quality audio scenes in which participants may change their relative positions. In this paper we describe and analyze an algorithm focused on maintaining relative synchronization between multiple users of such an environment and examine the subjective quality of service achieved

Catalase epitopes vaccine design for Helicobacter pylori: A bioinformatics approach

Bioinformatics tools are helpful for epitopes prediction directly from the genomes of pathogens in order to design a vaccine. Epitopes are sub-sequences of proteins (8 to 10 mer peptides) which bind to MHC to interact with the T cell receptors and stimulate immune responses. Finding a suitable vaccine against Helicobacter pylori is necessary, because of high prevalence of the infection (25 to 90%). Moreover, this bacteria has been classified as a grade I carcinogen by WHO since 1994. Catalase, an important enzyme in the virulence of H. pylori, could be a suitable candidate for vaccine design because it is highly conserved, which is important for the survival of H. pylori; it is expressed in high level and it is exposed on the surface of the bacteria. In this study, we designed epitope-based vaccine for catalase specific regions of H. pylori by means of immunobioinformatic tools. H. pylori (26695) catalase has been compared with human catalase in order to select specific regions. Afterwards, epitopes of catalase were determined by propred software. Among predicted epitopes, three epitopes were selected including, MVNKDVKQTT, VLLQSTWFL and FHPFDVTKI. Three candidates out of 51catalase antigen epitopes had the highest score for reactivating with MHC II MHC in propred software. The candidate epitopes for vaccine design should be rather a composition of considering epitopes: MVNKDVKQTTKKVLLQSTWFLKKFHPFDVTKI. In this manner, 39 of 51 alleles of MHC class ІІ were involved and stimulated T-cell responses. We believe prediction of catalase epitopes by the immunoinformatics tools would be valuable for developing new immuoprophylatic strategy against H. pylori infection.Key words: Helicobacter pylori, catalase, epitopes

Thermodynamic Analysis of a Compressed Air Energy Storage Facility Exporting Compression Heat to an External Heat Load

Fluctuations of electric load call for flexible generation technologies such as gas turbines. Alternatively, bulk energy storage (BES) facilities can store excess off-peak electricity to generate valuable peaking electricity. Interest in electricity storage has increased in the past decade in anticipation of higher penetration levels of intermittent renewable sources such as wind. Compressed Air Energy Storage (CAES) is one of the most promising BES technologies due to the large amount of energy (hundreds of MWh) that can be economically stored. CAES uses off-peak electricity to compress air into underground reservoirs. Air is combusted and expanded at a later time to regenerate electricity. One of the downsides of CAES is the large energy losses incurred in the form of waste compression heat. Distributed CAES (D-CAES) has been proposed in order to improve the roundtrip efficiency of CAES by utilizing the compression heat for space and water heating. The compressor of D-CAES is located near a heat load (e.g. a shopping mall) and the compression heat is recovered to meet this external load. D-CAES collects fuel credits equal to the negated heating fuel, leading to a higher overall efficiency compared to conventional CAES. We perform a thermodynamic analysis of conventional CAES and D-CAES to compare their heat rate, work ratio (electric energy stored per unit of electric energy regenerated), and exergy efficiency.Other Research Uni

Raman superradiance and spin lattice of ultracold atoms in optical cavities

We investigate synthesis of a hyperfine spin lattice in an atomic Bose-Einstein condensate, with two hyperfine spin components, inside a one-dimensional high-finesse optical cavity, using off-resonant superradiant Raman scattering. Spatio-temporal evolution of the relative population of the hyperfine spin modes is examined numerically by solving the coupled cavity-condensate mean field equations in the dispersive regime. We find, analytically and numerically, that beyond a certain threshold of the transverse laser pump, Raman superradiance and self-organization of the hyperfine spin components simultaneously occur and as a result a magnetic lattice is formed. The effects of an extra laser pump parallel to the cavity axis and the time-dependence of the pump strength on the synthesis of a sharper lattice are also addressed.Comment: Accepted for publication in New Journal of Physics. 16 pages and 6 figure

Optimized single-qubit gates for Josephson phase qubits

In a Josephson phase qubit the coherent manipulations of the computational states are achieved by modulating an applied ac current, typically in the microwave range. In this work we show that it is possible to find optimal modulations of the bias current to achieve high-fidelity gates. We apply quantum optimal control theory to determine the form of the pulses and study in details the case of a NOT-gate. To test the efficiency of the optimized pulses in an experimental setup, we also address the effect of possible imperfections in the pulses shapes, the role of off-resonance elements in the Hamiltonian, and the effect of capacitive interaction with a second qubit.Comment: 10 pages, 13 figure

Altered localisation of the copper efflux transporters ATP7A and ATP7B associated with cisplatin resistance in human ovarian carcinoma cells

Metals in Catalysis, Biomimetics & Inorganic Material