Phase-dependent interference fringes in the wavelength scaling of harmonic efficiency

We describe phase-dependent wavelength scaling of high-order harmonic generation efficiency driven by ultra-short laser fields in the mid-infrared. We employ both numerical solution of the time-dependent Schr\"{o}dinger equation and the Strong Field Approximation to analyze the fine-scale oscillations in the harmonic yield in the context of channel-closing effects. We show, by varying the carrier-envelope phase, that the amplitude of these oscillations depend strongly on the number of returning electron trajectories. Furthermore, the peak positions of the oscillations vary significantly as a function of the carrier-envelope phase. Owing to its practical applications, we also study the wavelength dependence of harmonic yield in the "single-cycle" limit, and observe a smooth variation in the wavelength scaling originating from the vanishing fine-scale oscillations.Comment: 5 pages, 4 figure

Rabi flopping between ground and Rydberg states with dipole-dipole atomic interactions

We demonstrate Rabi flopping of small numbers of $\rm{^{87}Rb}$ atoms between ground and Rydberg states with $n\le 43$. Coherent population oscillations are observed for single atom flopping, while the presence of two or more atoms decoheres the oscillations. We show that these observations are consistent with van der Waals interactions of Rydberg atoms.Comment: 4 pages, 6 figure

Genistein-induced mir-23b expression inhibits the growth of breast cancer cells

Aim of the study: Genistein, an isoflavonoid, plays roles in the inhibition of protein tyrosine kinase phosphorylation, induction of apoptosis, and cell differentiation in breast cancer. This study aims to induce cellular stress by exposing genistein to determine alterations of miRNA expression profiles in MCF-7 cells. Material and methods: XTT assay and trypan blue dye exclusion assays were performed to examine the cytotoxic effects of genistein treatment. Expressions of miRNAs were quantified using Real-Time Online RT-PCR. Results: The IC50 dose of genistein was 175 μM in MCF-7 cell, line and the cytotoxic effect of genistein was detected after 48 hours. miR-23b was found to be up-regulated 56.69 fold following the treatment of genistein. It was found that miR-23b was up-regulated for MCF-7 breast cancer cells after genistein treatment. Conclusions: Up-regulated ex-expression of miR-23b might be a putative biomarker for use in the therapy of breast cancer patients. miR-23b up-regulation might be important in terms of response to genistein. © 2015, Termedia Publishing House Ltd. All rights reserved

Fast Ground State Manipulation of Neutral Atoms in Microscopic Optical Traps

We demonstrate Rabi flopping at MHz rates between ground hyperfine states of neutral $^{87}$Rb atoms that are trapped in two micron sized optical traps. Using tightly focused laser beams we demonstrate high fidelity, site specific Rabi rotations with crosstalk on neighboring sites separated by $8 \mu\rm m$ at the level of $10^{-3}$. Ramsey spectroscopy is used to measure a dephasing time of $870 \mu\rm s$ which is $\approx$ 5000 times longer than the time for a $\pi/2$ pulse.Comment: 4 pages, 4 figure

Refractive Index Enhancement with Vanishing Absorption in an Atomic Vapor

We report a proof-of-principle experiment where the refractive index of an atomic vapor is enhanced while maintaining vanishing absorption of the beam. The key idea is to drive alkali atoms in a vapor with appropriate control lasers and induce a gain resonance and an absorption resonance for a probe beam in a two-photon Raman configuration. The strength and the position of these two resonances can be manipulated by changing the parameters of the control lasers. By using the interference between these two resonances, we obtain an enhanced refractive index without an increase in the absorption.Comment: 11 pages, 4 figure

Fundamental open questions on engineering of "super" hydrogen sorption in graphite nanofibers: relevance for clean energy applications

Herein, some fundamental open questions on engineering of “super” hydrogen sorption (storage) in carbonaceous nanomaterials are considered, namely: 1) on thermodynamic stability and related characteristics of some hydrogenated graphene layers nanostructures: relevance to the hydrogen storage problem; 2) determination of thermodynamic characteristics of graphene hydrides; 3) a treatment and interpretation of some recent STM, STS, HREELS/LEED, PES, ARPS and Raman spectroscopy data on hydrogensorbtion with epitaxial graphenes; 4) on the physics of intercalation of hydrogen into surface graphene-like nanoblisters in pyrolytic graphite and epitaxial graphenes; 5) on the physics of the elastic and plastic deformation of graphene walls in hydrogenated graphite nanofibers; 6) on the physics of engineering of “super” hydrogen sorption (storage) in carbonaceous nanomaterials, in the light of analysis of the Rodriguez-Baker extraordinary data and some others. These fundamental open questions may be solved within several years

Nanoscale addressing and manipulation of neutral atoms using electromagnetically induced transparency

We propose to integrate dark-state based localization techniques into a neutral atom quantum computing architecture and numerically investigate two specific schemes. The first scheme implements state-selective projective measurement by scattering photons from a specific qubit with very little cross talk on the other atoms in the ensemble. The second scheme performs a single-qubit phase gate on the target atom with an incoherent spontaneous emission probability as low as 0.01. Our numerical simulations in rubidium (Rb) atoms show that for both of these schemes a spatial resolution at the level of tens of nanometers using near-infrared light can be achieved with experimentally realistic parameters

Thermal analysis of wind turbine nacelle of 2.5 MW turbines at winter conditions

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.A numerical method for analysing and quantifying the thermal behaviour of wind turbine nacelle of 2.5 MW operating in the extreme winter conditions have been presented. The effects of the extreme external temperatures of -30oC, -20 C and -10oC on the electrical equipment and mechanical components within the nacelle have been determined at the design wind speed of 12 m/s. Two cases, open and closed system applications, have been considered. For both cases without the AC at Text=-30oC,the surface temperatures of the gear box and generator are outside the temperature limits. When applying the AC to the systems, temperatures became inside the operation temperature limits. For closed system applications at Text=-30 oC and -20 oC, the surface temperatures of all components are inside the temperature limits with the capacities of the AC system, 5 kg/s at 0 oC, 5 kg/s at 10oC with some icing problems inside wall of the nacelle. For closed system applications at Text=-10oC, the surface temperatures of components are inside the temperature limits with the AC capacities of 4 kg/s at 30oC, 5 kg/s at 0oC, 5 kg/s at 5oC and 5 kg/s at 10oC without icing problems. The simulation results have confirmed that, to maintain an acceptable temperature levels inside the nacelle and on the components for typical winter conditions, the air conditioning systems are needed. The air conditioning systems of the nacelle have to be optimized and adjusted properly as functions of wind turbines rated power, external wind velocity and temperatures.cf201