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The first application of time-dependent probability density function (PDF) analysis to the L-H transition in fusion plasmas is presented. PDFs have been constructed using Doppler Backscattering data of fluctuation velocity, u⊥, and turbulence from the edge region of the DIII-D tokamak. This raw time-series data has been sliced into millisecond-long sliding time-windows to create the PDFs. During the transition, the u⊥ PDFs develop strong right tails, which are indicative of turbulence-suppressing shear flows in the plasma edge region; such features and other subtle behaviours are explored using novel information geometry techniques. This paper highlights the power of these techniques to predict the onset of L-H transitions and support theories of predator-prey self-regulation between turbulence and shear flows.

The isotope dependence of the low- to high confinement-mode (L- to H-mode) transition power threshold P LH presents significant challenges for the initial (non-nuclear) hydrogen operations phase of the international thermonuclear experimental reactor (ITER). Here, we examine the isotope dependence of turbulence and E × B flow correlation properties in the L-mode edge plasma, leading up to the L-H transition. At marginal auxiliary power (near P LH ), turbulence is initially suppressed periodically during limit cycle oscillations (LCO) that precede the transition to sustained H-mode confinement. We present evidence that the long-range (toroidal) correlation of the E × B edge plasma flow across the LCO phase is much weaker in hydrogen than in deuterium in the DIII-D tokamak, congruent with the higher threshold power P LH required to access LCO and H-mode in hydrogen. Concomitantly, the time required to initially quench edge turbulence via localized edge E × B flow shear is significantly longer in hydrogen (1–1.5 ms) than in deuterium (approx. 100 µs). No toroidal long-range correlation of the turbulence amplitude is observed, in agreement with expectations based on the relatively short poloidal turbulence correlation length. Radial edge turbulence and flow correlation lengths are longer in deuterium than in hydrogen plasmas as one would expect from ‘naïve’ gyro-Bohm isotope transport scaling, despite the substantially higher thermal flux across the last closed flux surface in hydrogen before the L-H transition. This article is part of a discussion meeting issue 'H-mode transition and pedestal studies in fusion plasmas'.

The isotope dependence of the low- to high confinement-mode (L- to H-mode) transition power threshold

Detailed 2D turbulence measurements from the DIII-D tokamak provide an explanation for how resonant magnetic perturbations (RMPs) raise the L-H power threshold $P_\textrm{LH}$ [P. Gohil et al., Nucl. Fusion 51, 103020 (2011)] in ITER-relevant, low rotation, ITER-similar-shape plasmas with favorable ion $\nabla B$ direction. RMPs simultaneously raise the turbulence decorrelation rate $\Delta \omega_D$ and reduce the flow shear rate $\omega_\textrm{shear}$ in the stationary L-mode state preceding the L-H transition, thereby disrupting the turbulence shear suppression mechanism. RMPs also reduce the Reynolds stress drive for poloidal flow, contributing to the reduction of $\omega_\textrm{shear}$ On the ~100 {\mu}s timescale of the L-H transition, RMPs reduce Reynolds-stress-driven energy transfer from turbulence to flows by an order of magnitude, challenging the energy depletion theory for the L-H trigger mechanism. In contrast, non-resonant magnetic perturbations, which do not significantly affect $P_\textrm{LH}$, do not affect $\Delta \omega_D$ and only slightly reduce $\omega_\textrm{shear}$ and Reynolds-stress-driven energy transfer., Comment: The following article has been submitted to Physics of Plasmas

Forward and backward processes associated with the low-to-high (L-H) transition in magnetically confined fusion plasmas are investigated by using a time-dependent probability density function (PDF) approach and information length diagnostics. Our model is based on the extension of the deterministic prey–predator-type model [Kim and Diamond, Phys. Rev. Lett. 90, 185006 (2003)] to a stochastic model by including two independent, short-correlated Gaussian noises. The “forward” process consists of ramping up the input power linearly in time so that zonal flows self-regulate with turbulence after their initial growth from turbulence. The “backward” process ramps the power down again, by starting at time t = t * when the input power is switched to Q ( t ) = Q ( 2 t * − t ) for t > t *, linearly decreasing with time until t = 2 t *. Using three choices for Q(t), with differing ramping rates, the time-dependent PDFs are calculated by numerically solving the appropriate Fokker–Planck equation, and several statistical measures including the information length for the forward and backward processes are investigated. The information lengths L x ( t ) and L v ( t ) for turbulence and zonal flows, respectively, are path-dependent dimensionless numbers, representing the total number of statistically different states that turbulence and zonal flows evolve through in time t. In particular, PDFs are shown to be strongly non-Gaussian with convoluted structures and multiple peaks, with intermittency in zonal flows playing a key role in turbulence regulation. The stark difference between the forward and backward processes is captured by time-dependent PDFs of turbulence and zonal flows and the corresponding information length diagnostics. The latter are shown to give us a useful insight into understanding the correlation and self-regulation, and transition to the self-regulatory dithering phase.

We present gyrokinetic simulations with the GENE code addressing the near-edge region of an L-mode plasma in the DIII-D tokamak. At radial position $\rho=0.80$, simulations with the ion temperature gradient increased by $40\%$ above the nominal value give electron and ion heat fluxes that are in simultaneous agreement with the experiment. This gradient increase is consistent with the combined statistical and systematic uncertainty $\sigma$ of the Charge Exchange Recombination Spectroscopy (CER) measurements at the $1.6 \sigma$ level. Multi-scale simulations are carried out with realistic mass ratio and geometry for the first time in the near-edge. These multi-scale simulations suggest that the highly unstable ion temperature gradient (ITG) modes of the flux-matched ion-scale simulations suppress electron-scale transport, such that ion-scale simulations are sufficient at this location. At radial position $\rho=0.90$, nonlinear simulations show a hybrid state of ITG and trapped electron modes~(TEMs), which was not expected from linear simulations. The nonlinear simulations reproduce the total experimental heat flux with the inclusion of $\mathbf{E} \times \mathbf{B}$ shear effects and an increase in the electron temperature gradient by $\sim 23\%$. This gradient increase is compatible with the combined statistical and systematic uncertainty of the Thomson scattering data at the $1.3 \sigma$ level. These results are consistent with previous findings that gyrokinetic simulations are able to reproduce the experimental heat fluxes by varying input parameters close to their experimental uncertainties, pushing the validation frontier closer to the edge region., Comment: 14 pages, 17 figures, published in Physics of Plasmas

C-2 is a unique, large compact-toroid (CT) device at Tri Alpha Energy that produces field-reversed configuration (FRC) plasmas by colliding and merging oppositely directed CTs. Significant progress has recently been made on C-2, achieving ~5 ms stable plasmas with a dramatic improvement in confinement, far beyond the prediction from the conventional FRC scaling. This stable, long-lived FRC plasma state is called the high-performance FRC (HPF) regime. The key approaches to achieve the HPF regime are as follows: (i) dynamic FRC formation by collision/merging of super-Alfvenic CTs, (ii) effective control of stability and transport by end-on plasma guns and neutral-beam (NB) injection, and (iii) active wall conditioning using titanium and lithium gettering systems. Moreover, further improvement in FRC confinement has been obtained with improved open-field-line plasma properties such as a lower fluctuation level, reduced transport rates in radial/axial directions, and lower background neutral density a...

Aims There are significant variations in the published normal values of two-dimensional speckle tracking–derived strain and strain rate. These occur even when authors use the same software. To measure strain, the operator creates a region of interest (ROI) to define the myocardium to be analyzed. The purpose of this study was to test the hypothesis that measurements vary significantly with the chosen ROI width. Methods and Results In 20 healthy subjects (11 males, mean age 17.6 ± 6.18 years) an apical four-chamber view (4CH) and parasternal short-axis view (SAX) were analyzed. Initially ROI width was set automatically by the software. Two subsequent measurements were obtained from each cine loop by choosing the ROI width one step narrower and one step wider than the automatic ROI width. The mean differences between the measurements of narrower and automatic ROI and between automatic and wider ROI were −1.8 ± 0.7% and −0.9 ± 0.5% for global longitudinal strain (SL), −2.2 ± 0.6% and −1.7 ± 0.7% for global circumferential strain (SC), −0.10 ± 0.06/sec and −0.07 ± 0.06/sec for global longitudinal strain rate (SrL), and −0.15 ± 0.09/sec and −0.12 ± 0.07/sec for global circumferential strain rate (SrC) (all P

Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095, USAA high temperature, stable, long-lived field-reversed configuration (FRC) plasma state has been produced in the C-2 device by dynamically colliding and merging two oppositely directed compact toroids, with combining effects of biasing edge plasma near the FRC separatrix from an end-plasma-gun with magnetic-mirror-plugs andof neutral-beam (NB) injection. The plasma-gun creates an inward radial electric field which mitigates the n = 2rotational instability. The gun also produces E×B velocity shear in the FRC edge layer, which may explain observations of improved transport properties. The FRCs are nearly axisymmetric which enables fast ion confinement, and increasing NB power input clearly extends the FRC lifetime. The combined effects of the plasma-gun with mirror-plugs and of NB injection yield anew High Performance FRC regime with confinement times improved by factors 2 to 4 and FRC lifetimes extended from 1 to 3 ms.

Objective: The development of the left cardiac structures in the early life of small for gestational age (SGA) preterm infants has been inadequately studied. The aim of the study was to compare the left ventricular cardiac dimensions between SGA and appropriate for gestational age (AGA) preterm infants. Methods: Echocardiography was performed on day 2 (T1) and at age 1 month (T2) in 19 SGA preterm infants (birthweight rd percentile) and 21 AGA controls (P25-50) matched for gestational age ( Results: The left ventricular cardiac dimensions did not differ significantly between SGA and AGA infants at either T1 or T2 after correction for body length. The left ventricular mass was similar for SGA and AGA infants at T1 and T2 after correction for body weight or body length. The left ventricular output increased significantly from T1 to T2 in both SGA and AGA infants [SGA: 350 (T1)–640 (T2) mL/kg/min, P Conclusions: The left cardiac structures related to body length are comparable between SGA and AGA preterm infants in the first month of life and show similar development.

Objective To assess the prevalence and detection rate of major anomalies (MAs) by applying first trimester anomaly scan (FTAS) including first trimester fetal echocardiography (FTFE) to all fetuses and discuss ethical implications. Methods The study group included 6879 consecutive fetuses with known outcome of pregnancy (follow-up: 98%), 6565 with ‘normal’ nuchal translucency (NT) (≤P95), 314 with ‘increased’ NT (>P95). All fetuses received FTAS/FTFE. As MAs with the potential of being detected at FTAS/FTFE, we defined anomalies present at conception or developed during first trimester. Results Prevalence of MAs in fetuses with ‘normal’ NT reached 1.7%. Although 29.8% of chromosomal abnormalities were found in the group of ‘normal’ NT, 77% of MAs accompanied by a normal karyotype were found in this group. In fetuses with ‘normal’ NT and MA, diagnosis was made prenatally in 87.4% (FTAS/FTFE: 58.6%). Conclusion A relevant number of MA is present in fetuses with ‘normal’ NT. More than half will be detected by FTAS/FTFE. As consequence, one should discuss a concept in which also in fetuses with ‘normal’ NT, FTAS/FTFE should be offered. This concept can also be justified from an ethical point of view, which focuses on the principles of nonmaleficence, justice and respect for autonomy of the pregnant woman. © 2012 John Wiley & Sons, Ltd.

The Z-pinch driven fusion reactor will require extremely high current pulses to generate sufficient x-ray flux for the fusion target implosion. The fusion target is coupled to the pulsed power system through a recyclable transmission line (RTL) that is presently envisioned made of carbon steel. The energy released by the fusion pulse is absorbed by liquid flibe (Li 2 BeF 4 ) coolant and by the RTL material which is partially vaporized and ionized. The objective of this paper is to characterize the recombination of vaporized metal halides in the presence of ferritic steel in a plasma with parameters similar to those expected in the Z-IFE chamber (plasma density < 2x10 18 cm -3 , T e < 40000 K). Using a substitute eutectic salt (Na 2 MgCl 4 ) instead of flibe, we find experimentally that the three-body recombination rate of iron with chlorine is larger than that of sodium with chlorine. The measured recombination rates are compared to equilibrium recombination rates calculated at lower temperature (5000 K). The results suggest that an effective scheme for the removal of ferritic fluorite from the liquid flibe coolant may be needed in a Z-IFE reactor in addition to the mechanical separation of carbon steel RTL material required for recycling.

© 2015 IAEA, Vienna. In this paper we show that changing from an ion temperature gradient (ITG) to a trapped electron mode (TEM) dominant turbulence regime (based on linear gyrokinetic simulations) results experimentally in a strong density pump-out (defined as a reduction in line-averaged density) in low collisionality, low power H-mode plasmas. We vary the turbulence drive by changing the heating from predominantly ion heated using neutral beam injection to electron heated using electron cyclotron heating, which changes the ratio and the temperature gradients. Perturbed gas puff experiments show an increase in transport outside , through a strong increase in the perturbed diffusion coefficient and a decrease in the inward pinch. Linear gyrokinetic simulations with TGLF show an increase in the particle flux outside the mid-radius. In conjunction an increase in intermediate-scale length density fluctuations is observed, which indicates an increase in turbulence intensity at typical TEM wavelengths. However, although the experimental changes in particle transport agree with a change from ITG to TEM turbulence regimes, we do not observe a reduction in the core rotation at mid-radius, nor a rotation reversal.

A new diagnostic technique for determining neutral gas and metal vapor densities over a wide pressure range with high time resolution is described. A compact, current-stabilized hollow cathode/anode discharge is use to ionize the gas and/or trace impurity to be analyzed. We report proof-of-principle operation of the diagnostic in a well characterized argon discharge in the pressure range 6.7–265 Pa. The intensity ratio of neutral and singly ionized argon lines (IAr I/IAr II) is shown to increase monotonically with the neutral argon density. In a second experiment, absolute neutral lithium vapor densities have been measured using this diagnostic.

To study the impact of the maturational process of diastolic left ventricular function on trans-mitral Doppler flow parameters. In a survey we examined pulsed-wave Doppler signals and diastolic time intervals from 238 healthy neonates and infants. Using multiple linear regression analysis, we evaluated the impact of physiological determinants on parameter expression. Early-filling and atrial-filling peak velocities, early-filling acceleration and deceleration rates, and the atrial-filling time velocity integral reached a climax within 2 months after birth, while early-filling time velocity integral followed increasing throughout the study period. The isovolumic relaxation time was found to be significantly longer for neonates than for infants older than 2 months. The observed parameter movements could be attributed to changes of stroke volume and mitral valve area for early filling-time velocity integral (R2 = 0.93), and of heart rate, stroke volume, and mitral valve area for early filling peak velocity (R2 = 0.84), and atrial-filling time velocity integral (R2 = 0.65). Isovolumic relaxation time and atrial-filling peak velocity became heart rate dependent not before 3 months after birth. The observed parameter changes are powerful indicators for the maturational process in diastolic function. This process is mainly completed by 3 months of age.

We studied the influence of preload augmentation on Doppler-derived left ventricular diastolic function parameters in infants with a birth weight

Die Hypothese, dass progrediente Herzrhythmusstorungen und rechtsventrikulare Funktionsveranderungen miteinander zusammenhangen, wurde in einer prospektiven Querschnittsstudie an 42 Patienten nach Mustard-Operation getestet. Die Ventrikelfunktion wurde mit 2-D-Echokardiographie gemessen, Herzfrequenz und Rhythmusstorungen wurden mit 24-Stunden-Langzeit-EKG beurteilt. Eine Kohorte von 23 Patienten wurde 4,7±1,3 Jahre spater nachuntersucht, um die Ergebnisse der Querschnittsstudie zu validieren. Median des Operationsalters war 0,9 (0,02–8,5) Jahre. Bei Aufnahme der Patienten in die Querschnittsstudie oder in die Kohorte waren die Patienten 9,3 (1–18) bzw. 4,6 (0,9–13) Jahre alt. In der Querschnittsstudie sank die Ejektionsfraktion des rechten Ventrikels mit zunehmendem Alter (R=0,42, P=0,001). In der Kohorte nahm die Ejektionsfraktion von 0,51 (0,35–0,63) auf 0,47 (0,33–0,59) (P 0,1 ebenfalls mit dem Schweregrad der Sinusknotenerkrankung korreliert (Exp(B)=9,49, 95% CI 1,1–82, P

Der fehlerhafte Abgang der rechten Koronararterie aus der Pulmonalarterie ist selten, jedoch von erheblicher klinischer Relevanz. Diskussion: Wir berichten uber die Befunde eines asymptomatischen Schulkinds mit diesem Krankheitsbild und geben einen Uberblick uber diese Fehlbildung.

Background: Preterm infants may have cardiac stress related to patent ductus arteriosus (PDA) or bron-chopulmonary dysplasia (BPD). In this study, we examined the development of cardiac function in pre-term infants by measuring tissue Doppler–derived peak systolic strain (PSS) and strain rate (PSSR) in thefirst 28 days of life. Methods: Peak systolic strain and strain rate were measured in series in the free wallof the right (RV) and left (LV) ventricles on days 1, 7, 14, and 28 of life in 119 preterm infants

Aims To assess the effects of region of interest (ROI) size and strain length (SL) on the quality of analysis and to determine the feasibility and reproducibility of tissue Doppler–derived cardiac strain (S) and strain rate (SR) measurements for preterm infants

In this paper we show how changes in toroidal rotation, by controlling the injected torque, affect particle transport and confinement. The toroidal rotation is altered using the co- and counter neutral beam injection (NBI) in low collisionality H-mode plasmas on DIII-D (Luxon 2002 Nucl. Fusion 42 614) with dominant electron cyclotron heating (ECH). We find that there is no correlation between the toroidal rotation shear and the inverse density gradient, which is observed on AUG when is varied using ECH (Angioni et al 2011 Phys. Rev. Lett. 107 215003). In DIII-D, we find that in a discharge with balanced torque injection, the shear is smaller than the linear gyrokinetic growth rate for small for –0.85. This results in lower particle confinement. In the co- and counter- injected discharges the shear is larger or close to the linear growth rate at the plasma edge and both configurations have higher particle confinement. In order to measure particle transport, we use a small periodic perturbative gas puff. This gas puff perturbs the density profiles and allows us to extract the perturbed diffusion and inward pinch coefficients. We observe a strong increase in the inward particle pinch in the counter-torque injected plasma. Finally, the calculated quasi-linear particle flux, nor the linear growth rates using TGLF (Staebler et al 2005 Phys. Plasmas 12 102508) agree with experimental observations.

To assess the prevalence and detection rate of major anomalies (MAs) by applying first trimester anomaly scan (FTAS) including first trimester fetal echocardiography (FTFE) to all fetuses and discuss ethical implications.The study group included 6879 consecutive fetuses with known outcome of pregnancy (follow-up: 98%), 6565 with 'normal' nuchal translucency (NT) (≤ P95), 314 with 'increased' NT (P95). All fetuses received FTAS/FTFE. As MAs with the potential of being detected at FTAS/FTFE, we defined anomalies present at conception or developed during first trimester.Prevalence of MAs in fetuses with 'normal' NT reached 1.7%. Although 29.8% of chromosomal abnormalities were found in the group of 'normal' NT, 77% of MAs accompanied by a normal karyotype were found in this group. In fetuses with 'normal' NT and MA, diagnosis was made prenatally in 87.4% (FTAS/FTFE: 58.6%).A relevant number of MA is present in fetuses with 'normal' NT. More than half will be detected by FTAS/FTFE. As consequence, one should discuss a concept in which also in fetuses with 'normal' NT, FTAS/FTFE should be offered. This concept can also be justified from an ethical point of view, which focuses on the principles of nonmaleficence, justice and respect for autonomy of the pregnant woman.