Integrated bayesian estimation of Zeff on TEXTOR from Bremsstrahlung and CX Impurity density measurements

In a nuclear fusion experiment, the concept of an Integrated Data Analysis (IDA) allows the consistent estimation of plasma parameters from heterogeneous data sets [1]. Here, the determination of the ion effective charge (Zeff ), a critical local measure of impurity concentration, is considered. Several diagnostic methods exist for the determination of Zeff , but the results are in general not in agreement. Moreover, so far none of the available methods has provided a Zeff estimate that is reliable over the entire plasma cross-section, which is at present a real challenge. In this work, the problem of Zeff estimation is approached from the perspective of IDA, in the framework of Bayesian probability theory. The ultimate goal is the estimation of a full Zeff profile that is consistent both with measured bremsstrahlung emissivities, as well as individual impurity spectral line intensities obtained from Charge Exchange Spectroscopy (CXS). We present an overview of the various uncertainties that enter the calculation of a Zeff profile from bremsstrahlung data on the one hand, and line intensity data on the other hand. These appear at several levels, including the measurement process itself (together with independent electron density and temperature measurements), the inversion procedure (including knowledge of the magnetic equilibrium), the atomic data, the diagnostic calibrations, etc. We discuss a simple Bayesian model permitting the estimation of a central value for Zeff and the electron density ne on TEXTOR from bremsstrahlung emissivity measurements in the visible, and carbon densities derived from CXS. Both the central Zeff and ne are sampled using an MCMC algorithm. Extensions of the model to a full Bayesian analysis, incorporating all critical measurement and model uncertainties, are examined. Relevance to ITER through the pilot active beam experiment on TEXTOR is discussed. References: [1] R. Fischer and A. Dinklage, Rev. Sci. Instrum. 75, 4237 (2004)

Method to obtain absolute impurity density profiles combining charge exchange and beam emission spectroscopy without absolute intensity calibration

Investigation of impurity transport properties in tokamak plasmas is essential and a diagnostic that can provide information on the impurity content is required. Combining charge exchange recombination spectroscopy (CXRS) and beam emission spectroscopy (BES), absolute radial profiles of impurity densities can be obtained from the CXRS and BES intensities, electron density and CXRS and BES emission rates, without requiring any absolute calibration of the spectra. The technique is demonstrated here with absolute impurity density radial profiles obtained in TEXTOR plasmas, using a high efficiency charge exchange spectrometer with high etendue, that measures the CXRS and BES spectra along the same lines-of-sight, offering an additional advantage for the determination of absolute impurity densities

The two-pore channel TPC1 is required for efficient protein processing through early and recycling endosomes

Two-pore channels (TPCs) are localized in endo-lysosomal compartments and assumed to play an important role for vesicular fusion and endosomal trafficking. Recently, it has been shown that both TPC1 and 2 were required for host cell entry and pathogenicity of Ebola viruses. Here, we investigate the cellular function of TPC1 using protein toxins as model substrates for distinct endosomal processing routes. Toxin uptake and activation through early endosomes but not processing through other compartments were reduced in TPC1 knockout cells. Detailed co-localization studies with subcellular markers confirmed predominant localization of TPC1 to early and recycling endosomes. Proteomic analysis of native TPC1 channels finally identified direct interaction with a distinct set of syntaxins involved in fusion of intracellular vesicles. Together, our results demonstrate a general role of TPC1 for uptake and processing of proteins in early and recycling endosomes, likely by providing high local Ca2+ concentrations required for SNARE-mediated vesicle fusion

Cryo-electron tomography of cells: connecting structure and function

Cryo-electron tomography (cryo-ET) allows the visualization of cellular structures under close-to-life conditions and at molecular resolution. While it is inherently a static approach, yielding structural information about supramolecular organization at a certain time point, it can nevertheless provide insights into function of the structures imaged, in particular, when supplemented by other approaches. Here, we review the use of experimental methods that supplement cryo-ET imaging of whole cells. These include genetic and pharmacological manipulations, as well as correlative light microscopy and cryo-ET. While these methods have mostly been used to detect and identify structures visualized in cryo-ET or to assist the search for a feature of interest, we expect that in the future they will play a more important role in the functional interpretation of cryo-tomograms

Abstracts from the 8th International Conference on cGMP Generators, Effectors and Therapeutic Implications

This work was supported by a restricted research grant of Bayer AG