Experimental Realization of Quantum-Resonance Ratchets

Quantum-resonance ratchets associated with the periodically kicked particle are experimentally realized for the first time. This is achieved by using a Bose-Einstein condensate exposed to a pulsed standing light wave and prepared in an initial state differing from the usual plane wave. Both the standing-wave potential and the initial state have a point symmetry around some center and the ratchet arises from the non-coincidence of the two centers. The dependence of the directed quantum transport on the quasimomentum is studied. A detailed theoretical analysis is used to explain the experimental results.Comment: Accepted for publication in Physical Review Letters (November 2007

Sub-Fourier characteristics of a δ\delta-kicked rotor resonance

We experimentally investigate the sub-Fourier behavior of a $\delta$-kicked rotor resonance by performing a measurement of the fidelity or overlap of a Bose-Einstein condensate (BEC) exposed to a periodically pulsed standing wave. The temporal width of the fidelity resonance peak centered at the Talbot time and zero initial momentum exhibits an inverse cube pulse number ($1/N^{3}$) dependent scaling compared to a $1/N^{2}$ dependence for the mean energy width at the same resonance. A theoretical analysis shows that for an accelerating potential the width of the resonance in acceleration space depends on $1/N^{3}$, a property which we also verify experimentally. Such a sub-Fourier effect could be useful for high precision gravity measurements.Comment: 4 pages, 5 figure

Implications of surface noise for the motional coherence of trapped ions

Electric noise from metallic surfaces is a major obstacle towards quantum applications with trapped ions due to motional heating of the ions. Here, we discuss how the same noise source can also lead to pure dephasing of motional quantum states. The mechanism is particularly relevant at small ion-surface distances, thus imposing a new constraint on trap miniaturization. By means of a free induction decay experiment, we measure the dephasing time of the motion of a single ion trapped 50~$\mu$m above a Cu-Al surface. From the dephasing times we extract the integrated noise below the secular frequency of the ion. We find that none of the most commonly discussed surface noise models for ion traps describes both, the observed heating as well as the measured dephasing, satisfactorily. Thus, our measurements provide a benchmark for future models for the electric noise emitted by metallic surfaces.Comment: (5 pages, 4 figures

Scaling of NonOhmic Conduction in Strongly Correlated Systems

A new scaling formalism is used to analyze nonlinear I-V data in the vicinity of metal-insulator transitions (MIT) in five manganite systems. An exponent, called the nonlinearity exponent, and an onset field for nonlinearity, both characteristic of the system under study, are obtained from the analysis. The onset field is found to have an anomalously low value corroborating the theoretically predicted electronically soft phases. The scaling functions above and below the MIT of a polycrystalline sample are found to be the same but with different exponents which are attributed to the distribution of the MIT temperatures. The applicability of the scaling in manganites underlines the universal response of the disordered systems to electric field

Studies on Structural Defects on 60Co Irradiated Multi Walled Carbon Nanotubes.

AbstractAn attempt is made to study the effects of gamma irradiation on multi walled carbon nanotubes (MWCNTs) with a specific focus on surface modification, structural changes and identification of irradiation generated defects on their surface. The as-received MWCNTs were chemically treated in order to attach required functional group on the surface and to remove traces of metallic impurities. The MWCNTs were then gamma irradiated at 25, 50, 75 and 100 kGy doses. Micro Raman analysis was performed on irradiated MWCNTs to estimate the irradiation induced defects on their surface, which revealed that the number of defects increased with dose. XRD analysis was also performed to observe the same and it was revealed that the MWCNTs were subjected to micro-straining. The selective area electron diffraction pattern revealed that traces of amorphous carbon were formed after irradiation. Various defects such as bending, variation of internal and external diameter, wall damages formed on the MWCNTs was verified using TEM. It is concluded that subjecting MWCNTs to irradiation sources has produced structural changes and defects on their surface which can influence the properties of nanocomposites

Environmental Impacts of Ship Breaking and Recycling Industry of Sitakunda, Chittagong, Bangladesh

Ship dismantling of Bangladesh is a reason of concern due to its economic values and environmental hazards. This study focuses on the Ship Breaking and Recycling Industry (SBRI) of Bangladesh to assess the environmental impacts. It was done by analyzing the water quality parameters like, Turbidity, Salinity, Electric conductivity (EC), Dissolved Oxygen (DO), pH, Total Dissolved Solids (TDS), Temperature, Ammonia-Nitrogen, Nitrate–Nitrogen, Phosphate concentrations of inside and surroundings of Ship Breaking Yard. Turbidity ranged from 7.71 to 119 FTU in and 4.07 to 41.74 FTU in inside and outside the ship breaking yard, respectively. Salinity ranged from 0.95 to 14.28 ppt and 0.06 to 0.79 ppt in insde and outside, respectively. Value of EC varied from1.75 to 1280 µs/cm in inside and 0.21 to 15.7 µs/cm in outside, DO ranged from 3.77 to 7.94 mg/l in inside and 1.95 to 5.34 mg/l in outside. TDS value ranged from1280 to 15340 mg/l in inside and 74 to 825 mg/l in outside of ship breaking yard. Ammonia-N value ranged from 0.46 to 7.046 mg/l, Nitrate-N value ranged from 0.10 to 6.9 mg/l and Phosphate value ranged from 0.175 to 4.75 mg/l in the analyzed water sample. Magnitude of environmental alteration by establishment of ship breaking industry was assessed by quantifying Environmental impact value of Study area and the value was found as -93, where ecological parameters value was found -72, Physico-chemical parameters value was -70 and human interest value was found +49 which indicate negative alteration on environment

Discovery and Development of a Small Molecule Library with Lumazine Synthase Inhibitory Activity

(E)-5-Nitro-6-(2-hydroxystyryl)pyrimidine-2,4(1H,3H)-dione (9) was identified as a novel inhibitor of Schizosaccharomyces pombe lumazine synthase by high-throughput screening of a 100,000 compound library. The Ki of 9 vs. Mycobacterium tuberculosis lumazine synthase was 95 μM. Compound 9 is a structural analog of the lumazine synthase substrate, 5-amino-6-(D-ribitylamino)-2,4-(1H,3H)pyrimidinedione (1). This indicates that the ribitylamino side chain of the substrate is not essential for binding to the enzyme. Optimization of the enzyme inhibitory activity through systematic structure modification of the lead compound 9 led to (E)-5-nitro-6-(4-nitrostyryl)pyrimidine-2,4(1H,3H)-dione (26), which has a Ki of 3.7 μM vs. M. tuberculosis lumazine synthase