Electric field distortions in structures of the twist bend nematic (NTB) phase of a bent-core liquid crystal

Dielectric spectroscopy of a twist bend nematic phase of an achiral bent core liquid crystalline compound under DC bias is used to investigate its response to electric field. Two collective relaxation processes are revealed, these are assigned to distortions of helicoidal structure by the external bias field. Frequency of the mode depends primarily on the helicoidal angle and has anomalous, softening- like behaviour at the nematic to the twist bend nematic transition. A coupling of dielectric anisotropy with electric field gives rise to a new equilibrium periodic structure in the time scale involved. The modulus of the wave vector gradually vanishes on increasing the bias field (except for the initial behaviour, which is just the opposite). Transition from the twist bend to the splay bend structure is clearly observed by a sudden drop in the frequency of this mode, which decreases almost linearly with increasing field. Results agree with predictions from current models for the periodically distorted a twist bend nematic phase.Comment: 14 PAGES, 7 FIGURES, submitted to Physical Review Letter

Generation and detection of NOON states in superconducting circuits

NOON states, states between two modes of light of the form $|N,0\rangle+e^{i\phi}|0,N\rangle$ allow for super-resolution interformetry. We show how NOON states can be efficiently produced in circuit quntum electrodynamics using superconducting phase qubits and resonators. We propose a protocol where only one interaction between the two modes is required, creating all the necessary entanglement at the start of the procedure. This protocol makes active use of the first three states of the phase qubits. Additionally, we show how to efficiently verify the success of such an experiment, even for large NOON states, using randomly sampled measurements and semidefinite programming techniques.Comment: 15 pages and 3 figure

Magnetic field stabilization system for atomic physics experiments

Atomic physics experiments commonly use millitesla-scale magnetic fields to provide a quantization axis. As atomic transition frequencies depend on the amplitude of this field, many experiments require a stable absolute field. Most setups use electromagnets, which require a power supply stability not usually met by commercially available units. We demonstrate stabilization of a field of 14.6 mT to 4.3 nT rms noise (0.29 ppm), compared to noise of $\gtrsim$ 100 nT without any stabilization. The rms noise is measured using a field-dependent hyperfine transition in a single $^{43}$Ca$^+$ ion held in a Paul trap at the centre of the magnetic field coils. For the $^{43}$Ca$^+$ "atomic clock" qubit transition at 14.6 mT, which depends on the field only in second order, this would yield a projected coherence time of many hours. Our system consists of a feedback loop and a feedforward circuit that control the current through the field coils and could easily be adapted to other field amplitudes, making it suitable for other applications such as neutral atom traps.Comment: 6 pages, 5 figure

Prospectus, October 21, 1971

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Tube Width Fluctuations in F-Actin Solutions

We determine the statistics of the local tube width in F-actin solutions, beyond the usually reported mean value. Our experimental observations are explained by a segment fluid theory based on the binary collision approximation (BCA). In this systematic generalization of the standard mean-field approach effective polymer segments interact via a potential representing the topological constraints. The analytically predicted universal tube width distribution with a stretched tail is in good agreement with the data.Comment: Final version, 5 pages, 4 figure

Coupling JOREK and STARWALL for Non-linear Resistive-wall Simulations

The implementation of a resistive-wall extension to the non-linear MHD-code JOREK via a coupling to the vacuum-field code STARWALL is presented along with first applications and benchmark results. Also, non-linear saturation in the presence of a resistive wall is demonstrated. After completion of the ongoing verification process, this code extension will allow to perform non-linear simulations of MHD instabilities in the presence of three-dimensional resistive walls with holes for limited and X-point plasmas.Comment: Contribution for "Theory Of Fusion Plasmas, Joint Varenna - Lausanne International Workshop, Villa Monastero, Varenna, Italy (27.-31.8.2012)", accepted for publication in Journal of Physics Conference Serie

Lactobacillus delbrueckii ssp. bulgaricus B-30892 can inhibit cytotoxic effects and adhesion of pathogenic Clostridium difficile to Caco-2 cells

<p>Abstract</p> <p>Background</p> <p>Probiotic microorganisms are receiving increasing interest for use in the prevention, treatment, or dietary management of certain diseases, including antibiotic-associated diarrhea (AAD). <it>Clostridium difficile </it>is the most common cause of AAD and the resulting <it>C. difficile </it>– mediated infection (CDI), is potentially deadly. <it>C. difficile </it>associated diarrhea (CDAD) is manifested by severe inflammation and colitis, mostly due to the release of two exotoxins by <it>C. difficile </it>causing destruction of epithelial cells in the intestine. The aim of this study was to determine the effect of probiotic bacteria <it>Lactobacillus delbrueckii </it>ssp. <it>bulgaricus </it>B-30892 (LDB B-30892) on <it>C. difficile</it>-mediated cytotoxicity using Caco-2 cells as a model.</p> <p>Methods</p> <p>Experiments were carried out to test if the cytotoxicity induced by <it>C. difficile-</it>conditioned-medium on Caco-2 cells can be altered by cell-free supernatant (CFS) from LDB B-30892 in different dilutions (1:2 to 1:2048). In a similar experimental setup, comparative evaluations of other probiotic strains were made by contrasting the results from these strains with the results from LDB B-30892, specifically the ability to affect <it>C. difficile </it>induced cytotoxicity on Caco-2 monolayers. Adhesion assays followed by quantitative analysis by Giemsa staining were conducted to test if the CFSs from LDB B-30892 and other probiotic test strains have the capability to alter the adhesion of <it>C. difficile </it>to the Caco-2 monolayer. Experiments were also performed to evaluate if LDB B-30892 or its released components have any bactericidal effect on <it>C. difficile</it>.</p> <p>Results and discussion</p> <p>Co-culturing of LDB B-30892 with <it>C. difficile </it>inhibited the <it>C. difficile-</it>mediated cytotoxicity on Caco-2 cells. When CFS from LDB B-30892-<it>C. difficile </it>co-culture was administered (up to a dilution of 1:16) on Caco-2 monolayer, there were no signs of cytotoxicity. When CFS from separately grown LDB B-30892 was mixed with the cell-free toxin preparation (CFT) of separately cultured <it>C. difficile</it>, the LDB B-30892 CFS was inhibitory to <it>C. difficile </it>CFT-mediated cytotoxicity at a ratio of 1:8 (LDB B-30892 CFS:<it>C. difficile </it>CFT). We failed to find any similar inhibition of <it>C. difficile-</it>mediated cytotoxicity when other probiotic organisms were tested in parallel to LDB B-30892. Our data of cytotoxicity experiments suggest that LDB B-30892 releases one or more bioactive component(s) into the CFS, which neutralizes the cytotoxicity induced by <it>C. difficile</it>, probably by inactivating its toxin(s). Our data also indicate that CFS from LDB B-30892 reduced the adhesion of <it>C. difficile </it>by 81%, which is significantly (<it>P </it><0.01) higher than all other probiotic organisms tested in this study.</p> <p>Conclusion</p> <p>This study reveals the very first findings that <it>Lactobacillus delbrueckii </it>ssp. <it>bulgaricus </it>B-30892 (LDB B-30892) can eliminate <it>C. difficile</it>-mediated cytotoxicity, using Caco-2 cells as a model. The study also demonstrates that LDB B-30892 can reduce the colonization of <it>C. difficile </it>cells in colorectal cells. More study is warranted to elucidate the specific mechanism of action of such reduction of cytotoxicity and colonization.</p