Cubic boron nitride: a new prospective material for ultracold neutron application

For the first time, the neutron optical wall-potential of natural cubic boron nitride (cBN) was measured at the ultracold neutron (UCN) source of the research reactor TRIGA Mainz using the time-of-flight method (TOF). The samples investigated had a wall-potential of (305 +/- 15) neV. This value is in good agreement with the result extracted from neutron reflectometry data and theoretical expectations. Because of its high critical velocity for UCN and its good dielectric characteristics, cubic boron nitride coatings (isotopically enriched) will be useful for a number of applications in UCN experiments

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

The anomalous mole fraction effect in Chara: gating at the edge of temporal resolution.

The anomalous mole fraction effect (AMFE) of the K(+) channel in excised patches of the tonoplast of Chara showed a minimum of apparent open-channel current at 20 mM Tl(+) and 230 mM K(+). Time series obtained at a sampling rate of 100 kHz (filter 25 kHz) were analyzed by three methods to find out whether the AMFE results from an effect on gating or on the conductivity of the open state. Fitting the amplitude histograms by a superposition of gaussians showed a broadening in the presence of Tl(+). Dwell-time analysis based on an O-O-C-C-C model failed to evaluate rate constants above the filter frequency. Thus, the absence of any reduction of apparent open-channel current in time series simulated with the evaluated rate constants could not be taken as evidence against the hypothesis of gating. Finally, a direct fit of the measured time series using five different 5-state Hidden Markov models revealed that the presence of Tl(+) changed the rate constants in such a way that the number of transitions into the short-lived open state (30 micros) increased strongly compared to those in the absence of Tl(+). These models explain 25% reduction of apparent single-channel current amplitude through a rapid gating mechanism

Isolation and patch clamp measurements of xylem contact cells for the study of their role in the exchange between apoplast and symplast of leaves

Because of their importance for nutrition, a method was developed to patch xylem contact cells in leaves of Vicia Saba and maize. Since the lignification of older cells was a major obstacle for isolating protoplasts which could be patched, only young leaves (fourth fully developed leaf) were used. An important step in the isolation of these cells was the infiltration of the leaves and their exposure to enzymes for several hours, allowing mesophyll cells to be removed whilst having most of the xylem contact cells attached to the xylem. Channel activity in cell-attached mode or in excised patches could only be observed if an internal coating of sigmacote was used to block diffusion ions out of the pipette glass. Two different types of K+ channels were identified by measuring the reversal potential at different concentrations of KCl. One channel (SC) had a symmetric IV curve with a high probability of remaining open, irrespective of membrane potential; the other channel was an inward rectifier. The symmetical channel could be blocked weakly by Na+ but it was permeable to NH4(+)

Comparison of moisture-dependent orthotropic Young’s moduli of Chinese fir wood determined by ultrasonic wave method and static compression or tension tests

ISSN:0018-3768ISSN:1436-736