Towards a holographic dual of large-N_c QCD

We study N_f D6-brane probes in the supergravity background dual to N_c D4-branes compactified on a circle with supersymmetry-breaking boundary conditions. In the limit in which the resulting Kaluza--Klein modes decouple, the gauge theory reduces to non-supersymmetric, four-dimensional QCD with N_c colours and N_f << N_c flavours. As expected, this decoupling is not fully realised within the supergravity/Born--Infeld approximation. For N_f = 1 and massless quarks, m_q = 0, we exhibit spontaneous chiral symmetry breaking by a quark condensate, \neq 0, and find the associated massless `pion' in the spectrum. The latter becomes massive for m_q > 0, obeying the Gell-Mann--Oakes--Renner relation: M_pi^2= - m_q / \f_pi^2. In the case N_f > 1 we provide a holographic version of the Vafa--Witten theorem, which states that the U(N_f) flavour symmetry cannot be spontaneously broken. Further we find N_f^2 - 1 unexpectedly light pseudo-scalar mesons in the spectrum. We argue that these are not (pseudo) Goldstone bosons and speculate on the string mechanism responsible for their lightness. We then study the theory at finite temperature and exhibit a phase transition associated with a discontinuity in the chiral condensate. D6/anti-D6 pairs are also briefly discussed.Comment: 43 pages, LaTeX; v3: Scalar vs. pseudo-scalar nature of mesons clarified, references added. v4: Small change in Acknowledgment

Towards a new image processing system at Wendelstein 7-X: From spatial calibration to characterization of thermal events

Wendelstein 7-X (W7-X) is the most advanced fusion experiment in the stellarator line and is aimed at proving that the stellarator concept is suitable for a fusion reactor. One of the most important issues for fusion reactors is the monitoring of plasma facing components when exposed to very high heat loads, through the use of visible and infrared (IR) cameras. In this paper, a new image processing system for the analysis of the strike lines on the inboard limiters from the first W7-X experimental campaign is presented. This system builds a model of the IR cameras through the use of spatial calibration techniques, helping to characterize the strike lines by using the information given by real spatial coordinates of each pixel. The characterization of the strike lines is made in terms of position, size, and shape, after projecting the camera image in a 2D grid which tries to preserve the curvilinear surface distances between points. The description of the strike-line shape is made by means of the Fourier Descriptors

Forward modeling of collective Thomson scattering for Wendelstein 7-X plasmas: Electrostatic approximation

In this paper, we present a method for numerical computation of collective Thomson scattering (CTS). We developed a forward model, eCTS, in the electrostatic approximation and benchmarked it against a full electromagnetic model. Differences between the electrostatic and the electromagnetic models are discussed. The sensitivity of the results to the ion temperature and the plasma composition is demonstrated. We integrated the model into the Bayesian data analysis framework Minerva and used it for the analysis of noisy synthetic data sets produced by a full electromagnetic model. It is shown that eCTS can be used for the inference of the bulk ion temperature. The model has been used to infer the bulk ion temperature from the first CTS measurements on Wendelstein 7-X

Experimental confirmation of efficient island divertor operation and successful neoclassical transport optimization in Wendelstein 7-X

We present recent highlights from the most recent operation phases of Wendelstein 7-X, the most advanced stellarator in the world. Stable detachment with good particle exhaust, low impurity content, and energy confinement times exceeding 100 ms, have been maintained for tens of seconds. Pellet fueling allows for plasma phases with reduced ion-temperature-gradient turbulence, and during such phases, the overall confinement is so good (energy confinement times often exceeding 200 ms) that the attained density and temperature profiles would not have been possible in less optimized devices, since they would have had neoclassical transport losses exceeding the heating applied in W7-X. This provides proof that the reduction of neoclassical transport through magnetic field optimization is successful. W7-X plasmas generally show good impurity screening and high plasma purity, but there is evidence of longer impurity confinement times during turbulence-suppressed phases.EC/H2020/633053/EU/Implementation of activities described in the Roadmap to Fusion during Horizon 2020 through a Joint programme of the members of the EUROfusion consortium/ EUROfusio

Internet-based self-management compared with usual care in adolescents with asthma: a randomized controlled trial

Asthma control often is poor in adolescents and this causes considerable morbidity. Internet-based self-management (IBSM) improves asthma-related quality of life in adults. We hypothesized that IBSM improves asthma-related quality of life in adolescents. Adolescents (12-18 years) with persistent and not well-controlled asthma participated in a randomized controlled trial with 1 year follow-up and were allocated to IBSM (n = 46) or usual care (UC, n = 44). IBSM consisted of weekly asthma control monitoring with treatment advice by a web-based algorithm. Outcomes included asthma-related quality of life (Pediatric Asthma Quality of Life Questionnaire, PAQLQ) and asthma control (Asthma Control Questionnaire, ACQ) and were analyzed by a linear mixed-effects model. At 3 months, PAQLQ improved with 0.40 points (95% CI: 0.17-0.62, P < 0.01), by IBSM compared to 0.0 points for UC (P = 0.02 for the difference). At 12 months the between-group difference was -0.05 (95% CI: -0.50 to 0.41, P = 0.85). At 3 months ACQ improved more in IBSM than in UC (difference: -0.32 points; 95% CI: -0.56 to -0.079, P < 0.01). At 12 months the difference was -0.05 (95% CI: -0.35 to 0.25, P = 0.75). IBSM improved asthma-related quality of life and asthma control in adolescents with not well-controlled asthma after 3 months, but not after 12 month

Total testosterone in young men is more closely associated than free testosterone with prostate cancer disparities

Introduction: Early adulthood has been suggested as the most relevant time to determine the influence of testosterone on prostate carcinogenesis. For a more detailed assessment of this hypothesis, the present study examined whether serum total or free testosterone in young men was more closely associated with prostate cancer disparities