The effect of magnetic islands on ITG turbulence driven transport

In this work, we address the question of the influence of magnetic islands on the perpendicular transport due to steady-state ITG turbulence on the energy transport time scale. We demonstrate that turbulence can cross the separatrix and enhance the perpendicular transport across magnetic islands. As the perpendicular transport in the interior of the island sets the critical island size needed for growth of neoclassical tearing modes, this increased transport leads to a critical island size larger than that predicted from considering collisional conductivities, but smaller than that using anomalous effective conductivities. We find that on Bohm time scales, the turbulence is able to re-establish the temperature gradient across the island for islands widths $w \lesssim \lambda_{turb}$, the turbulence correlation length. The reduction in the island flattening is estimated by comparison with simulations retaining only the perpendicular temperature and no turbulence. At intermediate island widths, comparable to $\lambda_{turb}$, turbulence is able to maintain finite temperature gradients across the island

Perturbative approach to the nonlinear saturation of the tearing mode for any current gradient

Within the traditional frame of reduced MHD, a new rigorous perturbation expansion provides the equation ruling the nonlinear growth and saturation of the tearing mode for any current gradient. The small parameter is the magnetic island width w. For the first time, the final equation displays at once terms of order w ln(1/w) and w which have the same magnitude for practical purposes; two new O(w) terms involve the current gradient. The technique is applicable to the case of an external forcing. The solution for a static forcing is computed explicitly and it exhibits three physical regimes.Comment: 4 pages, submitted to Physical Review Letter

Plasma turbulence simulations with X-points using the flux-coordinate independent approach

In this work, the Flux-Coordinate Independent (FCI) approach to plasma turbulence simulations is formulated for the case of generic, static magnetic fields, including those possessing stochastic field lines. It is then demonstrated that FCI is applicable to nonlinear turbulent problems with and without X-point geometry. In particular, by means of simulations with the FENICIA code, it is shown that the standard features of ITG modes are recovered with reduced toroidal resolution. Finally, ITG turbulence under the influence of a static island is studied on the transport timescale with ITER-like parameters, showing the wide range of applicability of the method

Hemodynamic profiles of functional and dysfunctional forms of repetitive thinking

Background: The ability of the human brain to escape the here and now (mind wandering) can take functional (problem solving) and dysfunctional (perseverative cognition) routes. Although it has been proposed that only the latter may act as a mediator of the relationship between stress and cardiovascular disease, both functional and dysfunctional forms of repetitive thinking have been associated with blood pressure (BP) reactivity of the same magnitude. However, a similar BP reactivity may be caused by different physiological determinants, which may differ in their risk for cardiovascular pathology. Purpose: To examine the way (hemodynamic profile) and the extent (compensation deficit) to which total peripheral resistance and cardiac output compensate for each other in determining BP reactivity during functional and dysfunctional types of repetitive thinking. Methods: Fifty-six healthy participants randomly underwent a perseverative cognition, a mind wandering, and a problem solving induction, each followed by a 5-min recovery period while their cardiovascular parameters were continuously monitored. Results: Perseverative cognition and problem solving (but not mind wandering) elicited BP increases of similar magnitude. However, perseverative cognition was characterized by a more vascular (versus myocardial) profile compared to mind wandering and problem solving. As a consequence, BP recovery was impaired after perseverative cognition compared to the other two conditions. Conclusions: Given that high vascular resistance and delayed recovery are the hallmarks of hypertension the results suggest a potential mechanism through which perseverative cognition may act as a mediator in the relationship between stress and risk for developing precursors to cardiovascular disease

Low Rank Vector Bundles on the Grassmannian G(1,4)

Here we define the concept of $L$-regularity for coherent sheaves on the Grassmannian G(1,4) as a generalization of Castelnuovo-Mumford regularity on ${\bf{P}^n}$. In this setting we prove analogs of some classical properties. We use our notion of $L$-regularity in order to prove a splitting criterion for rank 2 vector bundles with only a finite number of vanishing conditions. In the second part we give the classification of rank 2 and rank 3 vector bundles without "inner" cohomology (i.e. H^i_*(E)=H^i(E\otimes\Q)=0 for any $i=2,3,4$) on G(1,4) by studying the associated monads.Comment: 11 pages, no figure

Functional fat injection in the treatment of dysphagia following surgery

Functional fat injection under local anesthesia could be useful in the treatment of chronic dysphagia in selected patients with tissue loss secondary to laryngeal surgery

Quantum theory of a polarization phase-gate in an atomic tripod configuration

We present the quantum theory of a polarization phase-gate that can be realized in a sample of ultracold rubidium atoms driven into a tripod configuration. The main advantages of this scheme are in its relative simplicity and inherent symmetry. It is shown that the conditional phase shifts of order $\pi$ can be attained.Comment: X International Conference on Quantum Optics, Minsk, Belaru

Vocalization-related stapedius muscle activity in different age chickens (Gallus gallus), and its role in vocal development

The stapedius muscle activity associated with vocalization was analyzed in young and adult roosters. Our results show that remarkable differences in the behavior of vocalization-related stapedius muscle activity exist between these two ages. Unlike young roosters, electrical stimulation in the midbrain of adult cocks yields vocalizations associated with stapedius muscle EMG responses that always show a higher threshold and a longer latency than those of the vocalization induced. Moreover, the maximal amplitude of the stapedius muscleEMG response is consistently lower than that detected in young roosters, despite the fact that the maximal vocalization amplitude of the adult birds is much higher. Onthewholeourresultsdemonstrate thatvocalization-relatedstapediusmuscleactivityisstronglyreducedinadulthood.Thepossibility that stapedius muscle may play a role during the vocal development was verified by comparing the crow of normal roosters with that of cocks from which the stapedius muscle had been removed shortly after hatching. Strong differences exist in the amplitude/frequency distribution of the crowing of normal and stapedectomized roosters, suggesting that the stapedius muscle exerts an important role in auditory feedback modulation, and that this feedback is used for normal vocal development