Intrinsic rotation with gyrokinetic models

The generation of intrinsic rotation by turbulence and neoclassical effects in tokamaks is considered. To obtain the complex dependences observed in experiments, it is necessary to have a model of the radial flux of momentum that redistributes the momentum within the tokamak in the absence of a preexisting velocity. When the lowest order gyrokinetic formulation is used, a symmetry of the model precludes this possibility, making small effects in the gyroradius over scale length expansion necessary. These effects that are usually small become important for momentum transport because the symmetry of the lowest order gyrokinetic formulation leads to the cancellation of the lowest order momentum flux. The accuracy to which the gyrokinetic equation needs to be obtained to retain all the physically relevant effects is discussed

Energetic Consistency and Momentum Conservation in the Gyrokinetic Description of Tokamak Plasmas

Gyrokinetic field theory is addressed in the context of a general Hamiltonian. The background magnetic geometry is static and axisymmetric, and all dependence of the Lagrangian upon dynamical variables is in the Hamiltonian or in free field terms. Equations for the fields are given by functional derivatives. The symmetry through the Hamiltonian with time and toroidal angle invariance of the geometry lead to energy and toroidal momentum conservation. In various levels of ordering against fluctuation amplitude, energetic consistency is exact. The role of this in underpinning of conservation laws is emphasised. Local transport equations for the vorticity, toroidal momentum, and energy are derived. In particular, the momentum equation is shown for any form of Hamiltonian to be well behaved and to relax to its magnetohydrodynamic (MHD) form when long wavelength approximations are taken in the Hamiltonian. Several currently used forms, those which form the basis of most global simulations, are shown to be well defined within the gyrokinetic field theory and energetic consistency.Comment: RevTeX 4, 47 pages, no figures, revised version updated following referee comments (discussion more strictly correct/consistent, 4 references added, results unchanged as they depend on consistency of the theory), resubmitted to Physics of Plasma

High-m Kink/Tearing Modes in Cylindrical Geometry

The global ideal kink equation, for cylindrical geometry and zero beta, is simplified in the high poloidal mode number limit and used to determine the tearing stability parameter, $\Delta^\prime$. In the presence of a steep monotonic current gradient, $\Delta^\prime$ becomes a function of a parameter, $\sigma_0$, characterising the ratio of the maximum current gradient to magnetic shear, and $x_s$, characterising the separation of the resonant surface from the maximum of the current gradient. In equilibria containing a current "spike", so that there is a non-monotonic current profile, $\Delta^\prime$ also depends on two parameters: $\kappa$, related to the ratio of the curvature of the current density at its maximum to the magnetic shear, and $x_s$, which now represents the separation of the resonance from the point of maximum current density. The relation of our results to earlier studies of tearing modes and to recent gyro-kinetic calculations of current driven instabilities, is discussed, together with potential implications for the stability of the tokamak pedestal.Comment: To appear in Plasma Physics and Controlled Fusio

Axisymmetric plasma equilibrium in gravitational and magnetic fields

Plasma equilibria in gravitational and open-ended magnetic fields are considered for the case of topologically disconnected regions of the magnetic flux surfaces where plasma occupies just one of these regions. Special dependences of the plasma temperature and density on the magnetic flux are used which allow the solution of the Grad–Shafranov equation in a separable form permitting analytic treatment. It is found that plasma pressure tends to play the dominant role in the setting the shape of magnetic field equilibrium, while a strong gravitational force localizes the plasma density to a thin disc centered at the equatorial plane

Enhanced binding revisited for a spinless particle in non-relativistic QED

We consider a spinless particle coupled to a quantized Bose field and show that such a system has a ground state for two classes of short-range potentials which are alone too weak to have a zero-energy resonance

Design, Synthesis and 5-HT1A Binding Affinity of N-(3-(4-(2-Methoxyphenyl)piperazin-1-yl)propyl)tricyclo[3.3.1.13,7 ]decan-1-amine and N-(3-(4-(2-Methoxyphenyl) piperazin-1-yl)propyl)-3,5-dimethyl-tricylo[3.3.1.13,7 ]decan-1-amine

Based on previously highlighted structural features, the development of highly selective 5-HT1A receptor inhibitors is closely linked to the incorporation of a 4-alkyl-1-arylpiperazine scaffold on them. In this paper, we present the synthesis of two new compounds bearing the 2-MeO-Ph-piperazine moiety linked via a three carbon atom linker to the amine group of 1-adamantanamine and memantine, respectively. Both were tested for their binding affinity against 5-HT1A receptor. N-(3-(4-(2-methoxyphenyl)piperazin-1-yl)propyl)tricyclo[3.3.1.13,7 ]decan-1-amine fumarate (8) and N-(3-(4-(2-methoxyphenyl)piperazin-1-yl)propyl)-3,5-dimethyl-tricylo[3.3.1.13,7 ]decan-1-amine fumarate (10) proved to be highly selective ligands towards 5-HT1A receptor with a binding constant of 1.2 nM and 21.3 nM, respectively, while 5-carboxamidotriptamine (5-CT) (2) was used as an internal standard for this assay with a measured Ki = 0.5 nM

Efeito acaricida in vitro de extratos de plantas do Pantanal no carrapato de bovinos, Rhipicephalus (Boophilus) microplus.

Estudou-se a ação acaricida dos extratos brutos etanólicos de 14 plantas do Pantanal sobre fêmeas ingurgitadas do carrapato-do-boi. Os bioensaios foram realizados em triplicatas pelo método de imersão das teleóginas e estimadas a produção de ovos, a eclodibilidade e a eficácia dos extratos. Extratos do lenho da raiz e da casca da raiz de Annona dioica, da raiz e da casca do caule de Simarouba versicolor, da raiz de Annona cornifolia e de Duguetia furfuracea tiveram atividade acaricida entre 50% e 100% e resposta dose-dependente. Extratos de Dimorphandra mollis, Magonia pubescens, Protium heptaphyllum, Hyptis crenata, Sebastiana hispida, Aspidosperma australe, Senna occidentalis e de Elyonurus muticus mostraram atividade acaricida baixa ou ausente (0% a 10%). Extratos da parte aérea de A. cornifolia, da planta inteira de Croton glandulosus e da casca do caule de Stryphnodendron obovatum mostraram atividade acaricida intermediária (10% a 20%). A alta atividade acaricida observada nos extratos de A. dioica, A. cornifolia e D. furfuracea indica ação de acetogeninas, moléculas naturais com várias atividades farmacológicas já descritas e presentes, principalmente, nas plantas da família Annonaceae.bitstream/CNPGC-2010/13215/1/BP26.pd

The evolution and consolidation of the timeshare industry in a developing economy: The South African experience

The timeshare industry is one of most under-researched aspects of tourism accommodation. Within existing scholarship most writings pertain to industry development and challenges in the USA and Europe. This paper provides an examination of the evolution and consolidation of the timeshare industry in South Africa from the 1980s to the present-day. The South African timeshare industry is revealed as one of the most mature in the international timeshare economy. Historically, the industry confronted parallel challenges to those in developed countries in respect of adapting the product to local conditions and confronting a tarnished image from the impact of unscrupulous developers. Currently the South African timeshare sector faces different challenges including service management and consumer dissatisfaction, marginalization within the tourism economy, and the need to address the emerging Black middle class market