The first probe measurements of edge turbulence and transport in a neutral beam induced high confinement mode (H-mode) are reported. A strong negative radial electric field is directly observed in H-mode. A transient suppression of normalized ion saturation and floating potential fluctuation levels occurs at the low confinement mode to high confinement mode (L–H) transition, followed by a recovery to near low mode (L-mode) levels. The average poloidal wave number and the poloidal wave-number spectral width are decreased, and the correlation between fluctuating density and potential is reduced. A large-amplitude coherent oscillation, localized to the strong radial electric field region, is observed in H-mode but does not cause transport. In H-mode the effective turbulent diffusion coefficient is reduced by an order of magnitude inside the last closed flux surface and in the scrape-off layer. The results are compared with a heuristic model of turbulence suppression by velocity-shear stabilization.

The theory of Alfven resonance effects on the wave modes of a tokamak is extended beyond the incompressible magnetohydrodynamic model to include finite-(u)/S2^) effects and compressibility. The discrete spectrum of compressional Alfven waves consists of a sequence of frequencies with finite damping decrements resulting from the Alfven resonance. The finite-frequency effects can cause the damping to almost vanish. This permits Alfven resonance heating via high-Q eigenmodes in large tokamaks.

In situ sensing of physiological and pathological species in cancer cells is of great importance to unravel their molecular and cellular processes. However, the biosensing with conventional probes is often limited by the undesired on-target off-tumor interference. Here, we report a novel strategy to design enzymatically controlled nanoflares for sensing and imaging molecular targets in tumor cells. The triggerable nanoflare was designed via rational engineering of structure-switching aptamers with the incorporation of an enzyme-activatable site and further conjugation on gold nanoparticles. The nanoflare sensors did not respond to target molecules in normal cells, but they could be catalytically activated by specific enzymes in cancer cells, thereby enabling cancer-specific sensing and imaging in vitro and in vivo with improved tumor specificity. Considering that diverse aptamers were selected, we expect that this strategy would facilitate the precise detection of a broad range of targets in tumors and may promote the development of smart probes for cancer diagnosis.

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We describe a way to parameterize power spectra extracted from fixed-frequency reflectometry data, with a view to systematic studies of turbulence properties in tokamak plasmas. Analysis of typical frequency spectra obtained from a new database suggests decomposition in a set of four key components: the direct current component, low-frequency fluctuations, broadband (BB) turbulence, and the noise level. For the decomposition in the identified components, different kinds of functions are tested and their fitting performance is analyzed to determine the optimal spectrum parametrization. In particular, for the BB turbulence, three models are compared qualitatively based on a number of representative spectrum test cases, notably the generalized Gaussian, the Voigt, and the Taylor model. In addition, quantitative performance testing is accomplished using the weighted residual sum of squares and the Bayesian information criterion in a large database including 350 000 spectra obtained in Tore Supra. Next, parametrization by the Taylor model is applied to Ohmically heated plasmas, and a BB energy basin is systematically observed in the core plasma region, which shrinks with decreasing radial position of the q = 1 surface. This basin might be explained by a drop of the density fluctuation level inside the q = 1 surface.

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Measurements of edge profiles, turbulence, and turbulentdriven transport were made inside the last-closed flux surface (LCFS) and in the scrape-off layer (SOL) of PBX-M L-mode and H-mode plasmas using a fast reciprocating Langmuir probe diagnostic. Direct measurements of the potential profile confirm the generation of a strong inward radial electric field (Er --100 V/cm) just inside the LCFS in Hmode. Density and potential fluctuation levels are reduced at the L-H transition, resulting in significantly lower turbulent transport. The edge density gradient then steepens in response to the reduced cross-field transport. After a stable H-mode edge equilibrium is formed, the fluctuation amplitudes recover back to nearly L-mode values. The poloidal wavenumber spectrum is narrowed in the transport barrier, and the density and potential fluctuations are decorrelated. The reduction in turbulent transport occurs