Simulating single-particle dynamics in magnetized plasmas: The RMF code.

The RMF (Rotating Magnetic Field) code is designed to calculate the motion of a charged particle in a given electromagnetic field. It integrates Hamilton's equations in cylindrical coordinates using an adaptive predictor-corrector double-precision variable-coefficient ordinary differential equation solver for speed and accuracy. RMF has multiple capabilities for the field. Particle motion is initialized by specifying the position and velocity vectors. The six-dimensional state vector and derived quantities are saved as functions of time. A post-processing graphics code, XDRAW, is used on the stored output to plot up to 12 windows of any two quantities using different colors to denote successive time intervals. Multiple cases of RMF may be run in parallel and perform data mining on the results. Recent features are a synthetic diagnostic for simulating the observations of charge-exchange-neutral energy distributions and RF grids to explore a Fermi acceleration parallel to static magnetic fields.

Formation of field-reversed-configuration plasma with punctuated-betatron-orbit electrons.

We describe ab initio, self-consistent, 3D, fully electromagnetic numerical simulations of current drive and field-reversed-configuration plasma formation by odd-parity rotating magnetic fields (RMF{o}). Magnetic-separatrix formation and field reversal are attained from an initial mirror configuration. A population of punctuated-betatron-orbit electrons, generated by the RMF{o}, carries the majority of the field-normal azimuthal electrical current responsible for field reversal. Appreciable current and plasma pressure exist outside the magnetic separatrix whose shape is modulated by the RMF{o} phase. The predicted plasma density and electron energy distribution compare favorably with RMF{o} experiments.

Formation of collisionless high-beta plasmas by odd-parity rotating magnetic fields.

Odd-parity rotating magnetic fields (RMFo) applied to mirror-configuration plasmas have produced average electron energies exceeding 200 eV at line-averaged electron densities of approximately 10(12) cm-3. These plasmas, sustained for over 10(3)tauAlfven, have low Coulomb collisionality, vc* triple bond L/lambdaC approximately 10(-3), where lambdaC is the Coulomb scattering mean free path and L is the plasma's characteristic half length. Divertors allow reduction of the electron-neutral collision frequency to values where the RMFo coupling indicates full penetration of the RMFo to the major axis.

Onset and saturation of ion heating by odd-parity rotating magnetic fields in a field-reversed configuration.

Heating of figure-8 orbit ions by odd-parity rotating magnetic fields (RMF(O)) applied to an elongated field-reversed configuration (FRC) is investigated. The largest energy gain occurs at resonances (s congruent to omega(R)/omega) of the RMF(O) frequency, omega(R), with the figure-8 orbital frequency, omega, and is proportional to s2 for s-even resonances and to s for s-odd resonances. The threshold for the transition from regular to stochastic orbits explains both the onset and saturation of heating. The FRC magnetic geometry lowers the threshold for heating below that in the tokamak by an order of magnitude.

Cardiovascular pharmacology of bombesin, a new polypeptide from amphibian skin.

Bombesin is a tetradecapeptide extracted from the side of discoglossid frogs Bombina bombina and Bombina variegata variegata. In anaesthetized dogs bombesin causes mainly systemic hypertension, bradycardia and constriction of the renal, mesenteric and coeliac arterial vessels. The other vascular beds studied (carotid, femoral and coronaric) passively follow the blood pressure. Tachyphylaxis may occur. Dibenzyline and hexamethonium do not antagonize the hypertensive property of bombesin, while the occlusion either of the renal vessels or of the mesenteric, coeliac arteries and portal vein reduces the intensity and the duration of the hypertensive response. The simultaneous occlusion of all the above mentioned vessels further reduces the duration of the hypertensive response evoked by bombesin and reverses its effect on the heart from mainly bradycardic to pure tachycardic. In these condition bombesin causes carotid and peripheral vasoconstriction. The increase of heart rate and of blood pressure, while occurs after ligation of aplanchnic vessels, is completely or partly antagonized by propranolol. In normal conscious dogs bombesin is at least 10 times more potent and less tachyphylactic than in anesthetized dogs.

The effects of catecholamines and adrenoceptor blocking drugs on the canine peripheral lymph flow.

Blood flow through the femoral artery, lymph flow in a lymphatic vessel in the femoral triangle and metatarsal distal venous pressure were measured simultaneously in a canine moving hind limb. 2. Low intra-arterial doses of adrenaline and noradrenaline increased lymph flow even in the presence of marked arterial vasoconstriction. In contrast, isoprenaline increased arterial blood flow without affecting lymph flow rate. 3. Phenoxybenzamine, dihydroergotoxine, and nicergoline did not inhibit the lymphatic flow increase induced by adrenaline at doses active on arterial or venous vascular alpha-adrenoceptors. 4. Propranolol given intra-arterially into animals pretreated with alpha-adrenoceptor blocking agents restored the vasoconstrictor effect of adrenaline (reversal of adrenaline reversal).