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The Kelvin-Helmholtz instability is a ubiquitous physical process in ordinary fluids and plasmas, frequently observed also in space environments. In this paper, kinetic effects at proton scales in the nonlinear and turbulent stage of the Kelvin-Helmholtz instability have been studied in magnetized collisionless plasmas by means of Hybrid Vlasov-Maxwell simulations. The main goal of this work is to point out the back reaction on particles triggered by the evolution of such instability, as energy reaches kinetic scales along the turbulent cascade. Interestingly, turbulence is inhibited when Kelvin-Helmholtz instability develops over an initial state which is not an exact equilibrium state. On the other hand, when an initial equilibrium condition is considered, energy can be efficiently transferred towards short scales, reaches the typical proton wavelengths and drives the dynamics of particles. As a consequence of the interaction of particles with the turbulent fluctuating fields, the proton velocity distribution deviates significantly from the local thermodynamic equilibrium, the degree of deviation increasing with the level of turbulence in the system and being located near regions of strong magnetic stresses. These numerical results support recent space observations from the Magnetospheric MultiScale mission of ion kinetic effects driven by the turbulent dynamics at the Earth's magnetosheath (Perri et al., 2020, JPlPh, 86, 905860108) and by the Kelvin-Helmholtz instability in the Earth's magnetosphere (Sorriso-Valvo et al., 2019, PhRvL, 122, 035102)., 14 pages, 11 figures

C-2 is a unique, large compact-toroid (CT) device at Tri Alpha Energy that produces field-reversed configuration (FRC) plasmas by colliding and merging oppositely directed CTs. Significant progress has recently been made on C-2, achieving ~5 ms stable plasmas with a dramatic improvement in confinement, far beyond the prediction from the conventional FRC scaling. This stable, long-lived FRC plasma state is called the high-performance FRC (HPF) regime. The key approaches to achieve the HPF regime are as follows: (i) dynamic FRC formation by collision/merging of super-Alfvenic CTs, (ii) effective control of stability and transport by end-on plasma guns and neutral-beam (NB) injection, and (iii) active wall conditioning using titanium and lithium gettering systems. Moreover, further improvement in FRC confinement has been obtained with improved open-field-line plasma properties such as a lower fluctuation level, reduced transport rates in radial/axial directions, and lower background neutral density a...

We analyze two situations where coherent properties of Alfvenic perturbations influence the behaviour of a turbulent system. The first case is a coronal loop where large scales are dominated by coherent fluctuations (eigenmodes) excited by resonance with motions at the loop bases. The input energy flux is mainly determined by the zero-frequency eigenmode which is independent of the background Alfven velocity profile; the resulting scaling law gives values compatible with the flux necessary to sustain the active-region corona. Nonlinear interactions are also influenced by coherence effects. From the resulting nonlinear flux a scaling law for the velocity perturbation is derived, which is compatible with measures of nonthermal velocities in corona. In second case we studied how monochromatic Alfven waves, propagating upward from the coronal base in a coronal hole region, develop small scales in form of a power-law spectrum when they go across a thin 3D inhomogeneous layer (∼104 km thick) located at the base of the corona. Though the obtained spectrum is steeper than what would be obtained by means of nonlinear interactions, it could influence the subsequent nonlinear dynamics of the system by reducing the time of heat deposition, with consequences on the acceleration of the solar wind.

The dynamics and the energy balance of large-scale fluctuations in a coronal loop are studied. The loop is represented by a simplified structure where the curvature is neglected and the background magnetic field is uniform. In a previous paper, we studied a similar model where a uniform background density was assumed. The present paper represents a generalization of the previous one and it has the purpose of investigating possible modifications to the large-scale energy balance and dynamics due to a more realistic longitudinally nonuniform density. Large-scale fluctuations are dominated by coherent eigenmodes that nonlinearly couple to produce an energy cascade to smaller scales. Eigenmodes properties are calculated by a simplified linear dissipative model, deriving an expression for the input energy flux that is not substantially modified by the presence of the density inhomogeneity and is independent of dissipation. For typical values of the parameters, the derived input energy flux is comparable with that required to heat the active region corona. Nonlinear couplings are dominated by coherence effects due to the symmetry properties of eigenmodes; the consequences are that the system is in a weakly nonlinear regime that produces fluctuating energy storage in the loop, and that the kinetic and magnetic nonlinear energy fluxes are of the same order, despite the dominance of magnetic energy at large scales. From the energy balance, an expression for the velocity fluctuation is derived, which is valid in the more general case of a nonuniform background density; this estimate is in agreement both with measures of nonthermal velocities in the solar corona and with previous numerical results.

We describe a numerical code to study the magnetohydrodynamic (MHD) turbulence in a reversed field pinch (RFP) configuration by solving the compressible MHD equations in cylindrical coordinates. The compressibility requires that particular attention should be paid to the boundary conditions to have an accurate control of wave reflections from the boundaries of the computational domain. To fulfill these requirements the boundary conditions are calculated by a decomposition into characteristic waves. We present a method to calculate such boundary conditions in curvilinear coordinates and we apply it to the solution of the MHD equations in cylindrical geometry.

Magnetic reconnection in an incompressible plasma in three-dimensional slab geometry has been studied through magnetohydrodynamics numerical simulations. Particular attention has been paid to the case in which several unstable modes that correspond to resonant surfaces in different positions of the simulation domain, are excited at the beginning of the simulation. The dynamical evolution of such a system leads to a behavior different than what is expected from the linear theory. In particular the effects of the equilibrium field dissipation and the fact that several resonant surfaces are initially excited both concur in modifying the initial growth rates of the instability. In the nonlinear phase two basic phenomena are observed: first, the rapid transfer of energy to large wave numbers, corresponding to a direct cascade of the energy in the spectrum, which approaches, with increasing time, a power law; second, an energy transfer towards smaller wave numbers, which corresponds in the physical space to a c...

In the prospect of employing 10 Gigabit Ethernet as networking technology for online systems and offline data analysis centers of High Energy Physics experiments, we performed a series of measurements on the performance of 10 Gigabit Ethernet, using the network interface cards mounted on the PCI-Express bus of commodity PCs both as transmitters and receivers. In real operating conditions, the achievable maximum transfer rate through a network link is not only limited by the capacity of the link itself, but also by that of the memory and peripheral buses and by the ability of the CPUs and of the Operating System to handle packet processing and interrupts raised by the network interface cards in due time. Besides the TCP and UDP maximum data transfer throughputs, we also measured the CPU loads of the sender/receiver processes and of the interrupt and soft-interrupt handlers as a function of the packet size, either using standard or ``jumbo'' Ethernet frames. In addition, we also performed the same measurements by simultaneously reading data from Fibre Channel links and forwarding them through a 10 Gigabit Ethernet link, hence emulating the behavior of a disk server in a Storage Area Network exporting data to client machines via 10 Gigabit Ethernet.

Di fronte alla costante crescita del costo dell'energia elettrica è ormai una pratica indispensabile la scelta di tecniche e sistemi a basso consumo per il miglioramento dell'efficienza energetica dei centri di calcolo. In questi centri ad alto fabbisogno energetico il raffreddamento delle apparecchiature informatiche rappresenta mediamente il 30% del consumo complessivo di energia elettrica, pertanto assume un'importanza strategica comprendere quali siano le condizioni più favorevoli per minimizzarne i costi di esercizio. Gli studi condotti sul tema hanno evidenziato i maggiori rendimenti delle macchine frigorifere a fronte dell'aumento delle temperature di esercizio all'interno delle sale calcolo, tantoché gli stessi produttori di apparecchiature informatiche propongono macchine in grado di operare a temperature sempre più alte e intervalli di umidità relativa sempre più ampi. Nel presente documento si descrive lo studio effettuato per il centro di calcolo Tier 1, presso il CNAF dell'INFN a Bologna, finalizzato alla valutazione dell'impatto che deriva dall'aumento delle temperature di esercizio nella sala calcolo, sia in termini di risparmio energetico ed economico sia in termini di ridondanza e resilienza dell'impianto. Lo studio si conclude con la stima del risparmio di energia elettrica consumata per il raffreddamento a fronte dell'innalzamento della temperatura di setpoint dell'acqua refrigerata da 8.5 °C a 14 °C, risparmio che si calcola del 14% circa.

The use of system modelling tools for design and transient analysis of LRE is becoming more and more common since their accuracy is constantly improving. But for this kind of tools prediction of lm cooling e ectiveness is still a challenging problem. A lm cooling model capable of describing the bene ts of such a cooling technique, as well as the impacts on the propulsion system such as loss in performance and requirements induced on other subsystems, can support the preliminary design of LRE systems. EcosimPro is an object oriented tool capable of modelling various kinds of dynamic systems. The model described within this paper is implemented alongside ESPSS the propulsion system library compatible with EcosimPro. This paper covers a Quasi 2-D integral formulation to study the developed ow eld of a lm wall jet in combustion chambers. With this approach it is possible to have a fast prediction of the evolution in space and time of both coolant and wall temperature distribution therefore also of the lm cooling e ectiveness. A new model is here presented: a \layered model" based on the assumption that the mixing zone does not a ect the lm and mainstream ows but it is a result of their interaction. The geometry of the developed ow eld is based on the one carried out by Simon and it accounts for the core, mixing and lm regions. The governing equations already present in the original combustion chamber model are used as a starting point. The implementation here described can easily be embedded in an unsteady propulsion system analysis for simulating the its transient phases and steady state operation points. The code exibility allows for using the same model also for performance analysis in steady-state, and for o -design studies. First validation results are given here, in particular a DLR H2/O2 combustion chamber lm cooling test campaign has been taken as reference case for validation purposes.

During the start-up of a liquid rocket engine most of the engine components are required to work at extreme operating conditions; this phase features very complex phenomena such as combustion instabilities, water hammer e ects in feed lines, turbopumps operating far from design conditions and two-phase ows that cannot be neglected when design studies of an engine are to be performed or the assessment of the valve opening sequence has to be done. For these reasons simulations of the ignition transient phase become necessary in order to reduce the experimental tests and increase the engine safety and reliability. The subject of the present work is to develop an LRE transient model, to apply it to simulate the start-up transient and to validate the model with an existing liquid rocket engine (the RL-10). A system approach has been used, since it is necessary to take into account all the interactions between all the components of an engine. This choice is fundamental if a detailed estimation of the engine transient behaviour is the task. The system simulated by the code encompasses the complete feeding system from the tanks down to the the turbopump subsystems, the valves, the pipes, the thrust chamber’s inlets, the ow ducts of the thrust chamber itself and the chemical reactions inside the combustion chamber. The engine model is built using ESPSS, the propulsion system library compatible with EcosimPro, an object oriented tool capable of modelling various kinds of dynamic systems. The engine model includes also original models developed by the authors and presented in previous works such as a new injector plate model, and more realistic heat transfer coe cient correlations. The transient phase of the Pratt&Whitney RL-10 engine has been taken as validation case. This engine has been chosen for several reasons, among which the good availability of engine construction data, performance and tests results in open literature. The main subsystem models of this engine will be described and their validation will be presented. Then the integrated model of the entire engine will be described alongside the comparison of the simulation with experimental data.

A compressible magnetohydrodynamics simulation of the reversed-field pinch is performed including anisotropic thermal conductivity. When the thermal conductivity is much larger in the direction parallel to the magnetic field than in the perpendicular direction, magnetic field lines become isothermal. As a consequence, as long as magnetic surfaces exist, a temperature distribution is observed displaying a hotter confined region, while an almost uniform temperature is produced when the magnetic field lines become chaotic. To include this effect in the numerical simulation, we use a multiple-time-scale analysis, which allows us to reproduce the effect of a large parallel thermal conductivity. The resulting temperature distribution is related to the existence of closed magnetic surfaces, as observed in experiments. The magnetic field is also affected by the presence of an anisotropic thermal conductivity.

uid ow formulation. EcosimPro is an object oriented tool capable of modelling various kinds of dynamic systems. The model described within this paper is implemented alongside ESPSS, 1 the propulsion system library compatible with EcosimPro. This paper covers a new simplied \Quasi-2D" approach to study the coupled problem of coolant ow and wall structure heat transfer in the cooling channels of a liquid rocket engine from a system point of view. With this approach it is possible to have a fast prediction of the evolution in space and time of both coolant and wall temperature distribution. Unlike the previous models used to evaluate thermal stratication, this one is based on 1D unsteady mass governing equation, and \Quasi-2D" momentum and energy conservation equations. For each longitudinal node, the channel is divided into slices. The governing equations take into account the shear stresses between the slices and the heat uxes in vertical direction due to turbulent mixing. The model hereafter described can be easily embedded in an unsteady propulsion system analysis for simulating the ignition transient. The code exibility allows for using the same model also for performance analysis in steady-state, and for o-design studies. Numerical test cases from the University of Rome, 5 and experimental test cases from the German Aerospace Center (DLR) 10 will be simulated and their results will be compared with the simulation results of the model.

The energy balance at large scales in a coronal loop is studied, using an analytical model. We generalize a previous model by including a longitudinal inhomonegeity in the background density. The dynamics is regulated by the resonance between motions at the loop basis and eigenmodes, giving rise to energy storage within the loop, and by nonlinear effects that move this energy to smaller scales. We derive a scaling law for the input energy flux, the properties of eigenmodes and of their nonlinear coupling, and estimations for the nonlinear flux and for the velocity perturbation. For typical loop conditions, the resulting values are in accordance with the energy flux required for the quiet‐Sun corona and with measured nonthermal velocities.

We study the reversed-field pinch through the numerical solution of the compressible magnetohydrodynamic equations. Two cases are investigated: In the first case the pressure is derived from an adiabatic condition, and in the second case the pressure equation includes heating terms due to resistivity and viscosity. In the adiabatic case a single helicity state is observed, and the reversed-field pinch configuration is formed for short time intervals and is finally lost. In the nonadiabatic case the system reaches a multiple helicity state, and the reversal parameter remains negative for a longer time. The results show the importance of compressibility in determining the large scale dynamics of the system.

The knowledge of the flow behavior inside cooling channels is of great importance to improve design and performance of regeneratively cooled rocket engines. The modeling of the coolant flow is a challenging task because of its particular features, such as the high wall temperature gradient, the high Reynolds number and the 3D-geometry of the passages. In case of methane as coolant, a further complication is the transcritical operating condition of the fluid. In this thermodynamic regime large changes of the fluid properties can greatly influence the coolant flow field and the heat transfer. Numerical simulations of transcritical methane flow field in asymmetrically heated rectangular channel with high aspect ratio and strong wall temperature differences are carried out by a suitable NavierStokes solver. Results are discussed in detail and compared with a supercritical flow field. Finally the aspect ratio effect on transcritical methane flows is analyzed by comparison of four different rectangular cooling channels geometries. Emphasis is given to the comparison of wall heat flux distribution and fluid cooling performance.

The anisotropy properties of magnetohydrodynamic turbulence in a sheared magnetic field are analyzed through a three-dimensional numerical simulation that reproduces the linear and nonlinear stage of a tearing instability. Far from the current sheet, the energy spectrum develops perpendicularly to the local magnetic field, as in homogeneous configurations. Within the current sheet, the spectrum anisotropy is also affected by the structure of unstable modes. With increasing time, the configuration becomes more turbulent, the former effect disappears, and the energy cascade takes place perpendicularly to the local magnetic field. The local spectrum becomes increasingly anisotropic while the spatially integrated spectrum tends to isotropize. There is the possibility that these properties could be used to identify the nonlinear stage of magnetic reconnection in space and laboratory plasmas, as well as to identify the particle transport regime in the considered magnetic configuration.

CFD codes typically treat fluid/solid boundary conditions in a simplified manner such as constant prescribed temperature or heat flux with zero mass transfer. However, thermal protection materials (TPS) strongly interact with the flow so that simple CFD surface boundary conditions cannot realistically be used for TPS design. In order to obtain a better estimation of the wall heat flux over an ablating surface, a two-dimensional axisymmetric full Navier-Stokes equation solver is used coupled with surface mass and energy balance and an equilibrium ablation model for graphite. Flat plate tests are presented. Results are compared with the most commonly used simplified approaches.

Although a coronal hole is permeated by a magnetic field with a dominant polarity, magnetograms reveal a more complex magnetic structure in the lowest layers, where several regions of opposite polarity of typical size of the order of 104 km are present. This can give rise to magnetic separatrices and neutral lines. MHD fluctuations generated at the base of the coronal hole by motions of the inner layer of the solar atmosphere may interact with such inhomogeneities, leading to the formation of small scales. This phenomenon is studied on a 2D model of a magnetic structure with an X-point, using 2D MHD numerical simulations. This model implements a method of characteristics for boundary conditions in the direction outer-pointing to Sun surface to simulate both wave injection and exit without reflection. Both Alfvenic and magnetosonic perturbations are considered, and they show very different phenomenology. In the former case, an anisotropic power-law spectrum forms with a dominance of perpendicular wavevectors at altitudes ~104 km. Density fluctuations are generated near the X-point by Alfven wave magnetic pressure and propagate along open fieldlines at a speed comparable to the local Alfven velocity. An analysis of energy dissipation and heating caused by the formation of small scales for the Alfvenic case is presented. In the magnetosonic case, small scales form only around the X-point, where a phenomenon of oscillating magnetic reconnection is observed to be induced by the periodic deformation of the magnetic structure due to incoming waves.

About 50% of patients with cryptogenic stroke have a patent foramen ovale (PFO). The recurrence rate of paradoxical embolism is higher if a PFO is detected.Thirty-five patients with PFO andor = 1 thromboembolic event due to paradoxical embolism were included in the study (23 males, 12 females, mean age 47.8 +/- 14 years, mean weight 75 +/- 15 kg). Twenty-three patients had a transient ischemic attack whereas 12 experienced an ischemic stroke. Twenty-nine patients had one thromboembolic event, 4 patients had two thromboembolic events, and 2 patients had three thromboembolic events. The implantation procedure was performed, as previously reported, under general anesthesia, fluoroscopic guidance and during transesophageal echocardiography.The implantation procedure was successful in all patients. There were no complications related to the procedure. Four different devices were implanted (Amplatzer 3 patients; Cardioseal 12 patients; Starflex 12 patients, PFO Star 8 patients). The procedure time and fluoroscopic time were 50 +/- 21.8 and 12.2 +/- 8.3 min respectively. At transesophageal echocardiography performed after the procedure, 11 patients had a trivial shunt. None of the patients had a residual shunt at 1 month of follow-up. The mean follow-up was 12.3 +/- 8 months (median 11.0 months, range 3-37 months). In no patient did recurrence of a thromboembolic event occur during follow-up.Percutaneous PFO closure is a feasible and safe technique for the prevention of recurrent paradoxical embolism.

Rapid technological developments have made new materials available for percutaneous coronary intervention procedures. The coronary stent in particular has undergone progressive structural improvements leading to the recent availability of a third generation of stents, namely, coated stents. The rapid evolution of the stent has often made its evaluation problematical, since trials are frequently confined to small groups of patients in single centers. The purpose of this registry was to verify the safety and efficacy of the BiodivYsio stent (a stent coated with phosphorylcholine polymer) in a broad population of patients who reflect the daily reality of coronary intervention in a cardiac catheterization laboratory.The registry was designed to collect the principal angiographic and clinical data of a consecutive series of Oreal worldO patients. Patients were treated with a BiodivYsio stent (Biocompatibles, Galway, United Kingdom) in 12 centers (11 Italian and 1 Swiss) between January 1998 and January 1999. Procedural, in-hospital, 30-day and six-month follow-up data were collected. The monitoring, data entry and statistical analyses were carried out by an independent center. During the study, 218 patients were enrolled; 165 (76%) male and 53 (24%) female, with an average age of 61.6 +/- 9.4 years (range, 36Eth 84 years). A total of 258 stents were implanted in 233 lesions (1.1 stents per lesion), of which 233 (90%) were the BiodivYsio PC coated stent, the remaining 25 implants were of other stent types. The percutaneous transluminal coronary angioplasty and stenting procedure were carried out in 109 (50%) patients with unstable angina, 65 (30%) with stable angina, 29 (13%) with acute myocardial infarction, and 15 (7%) patients with silent ischemia. Procedural success was achieved in 217/218 (99.5%) patients. Optimal results were achieved in 212 (97.7%) patients. In 34 (15.6%) cases, patients were treated with periprocedural abciximab. During the hospitalization period, one (0.4%) death occurred on day 7 due to subacute occlusion of the stent, and 3 (1.4%) myocardial infarctions were reported. At 30-day follow-up, 211 (97.2%) patients were asymptomatic, as were 189 (87%) patients at clinical follow-up at 6 months.This study evaluated the safety and efficacy of a third-generation stent. The results demonstrate a high procedural success rate and a low incidence of major adverse cardiac events at short- and medium-term follow-up. It appears that the BiodivYsio stent should be considered safe in clinical and/or anatomical situations with a high risk of complications, confirming the hypothesis that PC may have non-thrombogenic properties. To corroborate these results, an appropriately designed study would be required to measure the stentOs efficacy in the most suitable clinical context, i.e., clinical situations that are at the highest risk of ischemic relapse.

Plug nozzles have received renewed attention in the frame of future launcher developments. Their use appears particularly convenient for Single Stage to Orbit vehicles, because of the overall improvement in performance and also of their possible good integration with the vehicle shape. Nevertheless, a better understanding of the phenomena that take place is necessary, in order to evaluate accurately their behavior. The numerical and experimental analysis of two linear plug nozzle models, performed for different truncation lengths, has allowed to emphasize the critical points of the design. Moreover, the comparisons of numerical and experimental data indicate limitations and expectations for either approach to be used for analyzing their behavior.

This study aimed to compare the hearing changes in the long term after vestibular neurectomy, endolymphatic mastoid shunt, and medical treatment in classic Meniere's disease.A retrospective case review was conducted based on audiologic follow-up between 5 and 21 years.The study was performed at two centers in Bari University Hospital, one performing vestibular neurectomy as the first surgical procedure for Meinere's disease and the other, endolymphatic mastoid shunt.Of 68 patients with intractable idiopathic Meniere's disease, 29 underwent middle fossa vestibular neurectomy, and 17 had endolymphatic mastoid shunt; 22 were offered surgery but declined.Outcome measures were puretone average (PTA), speech reception threshold, and speech discrimination score before and after treatment.PTA declined by an average of 9.3 dB in neurectomy patients, 13.3 dB in patients undergoing endolymphatic mastoid shunt, and 18.1 dB in patients who were offered surgery but declined. Patients were subdivided into two cohorts based on their preoperative or initial PTA. In the patients who had PTA scores worse than 50 dB initially, the PTA declined an average of 4.3 dB in the vestibular neurectomy group, 11.5 dB in the endolymphatic sac group, and 4 dB in the nonsurgical group. In the patients with PTAor = 50 dB initially, the PTA declined an average of of 25.3 dB in the vestibular neurectomy group, 16.1 in the endolymphatic sac group, and 26.2 dB in the nonsurgical group. Although shunt patients with good hearing initially deteriorated less than neurectomy patients and less than patients who declined surgery, the difference was not significant.These results indicate that patients with poor hearing stabilized, while patients with good hearing continued to deteriorate. The same conditions were observed in the patients who had surgery and those who were offered surgery but declined.

Compressible magnetohydrodynamics simulations of the reversed-field pinch (RFP) are presented. Previous simulations of the RFP, including density and pressure evolution, showed that a stationary state with a reversed toroidal magnetic field could not be obtained, contrary to the results produced with numerical codes neglecting density and pressure dynamics. The simulations described in the present paper show that including density and pressure evolution, a stationary RFP configuration can be obtained if the resistivity has a radial profile steeply increasing close to the wall. Such resistivity profile is more realistic than a uniform resistivity, since the temperature at the wall is lower than in the plasma core.

INFN-CNAF is the central computing facility of INFN: it is the Italian Tier-1 for the experiments at LHC, but also one of the main Italian computing facilities for several other experiments such as BABAR, CDF, SuperB, Virgo, Argo, AMS, Pamela, MAGIC, Auger etc. Currently there is an installed CPU capacity of 100,000 HS06, a net disk capacity of 9 PB and an equivalent amount of tape storage (these figures are going to be increased in the first half of 2012 respectively to 125,000 HS06, 12 PB and 18 PB). More than 80,000 computing jobs are executed daily on the farm, managed by LSF, accessing the storage, managed by GPFS, with an aggregate bandwidth up to several GB/s. The access to the storage system from the farm is direct through the file protocol. The interconnection of the computing resources and the data storage is based on 10 Gbps technology. The disk-servers and the storage systems are connected through a Storage Area Network allowing a complete flexibility and easiness of management; dedicated disk-servers are connected, also via the SAN, to the tape library. The INFN Tier-1 is connected to the other centers via 3×10 Gbps links (to be upgraded at the end of 2012), including the LHCOPN and to the LHCONE. In this paper we show the main results of our center after 2 full years of run of LHC.

We perform numerical simulations of gravity mode propagation in a convective layer to investigate the observed association between small spatial scales and low frequencies in the photospheric velocity fields. According to the linear theory, when the fluid layer is convectively unstable, gravity modes are evanescent waves. However, in simple two-dimensional numerical settings, we find that when the equilibrium structure is modified by coherent large-scale convective motions, the waves injected at the bottom of the layer are no longer evanescent. In this situation, gravity waves can be detected at the surface of the layer. In our simplified model the injected wave's frequency remains unchanged, but its amplitude has a spatial modulation determined by the convective structure. This result may explain some analyses done with the proper orthogonal decomposition method of the solar surface velocity field even though solar convection is far more complex than the convection model considered here.

Using a magnetohydrodynamics numerical code that includes the description of density and pressure evolution and anisotropic thermal conductivity, it is shown that single-helicity states in the reversed-field pinch (RFP) configuration are obtained when the resistivity has a radial profile sharply increasing close to the wall. In contrast, a uniform resistivity produces multiple-helicity states. A radially increasing resistivity profile is determined in RFP experiments by the temperature difference between the plasma core and the wall. The results of the simulations presented in this letter are an indication that quasi-single-helicity states observed in experiments with high toroidal currents may be a consequence of the resistivity profile determined by the high temperatures reached in the plasma core in high-current discharges.

Two compressible magnetohydrodynamics simulations of the reversed-field pinch are performed, with isotropic and anisotropic thermal conductivity. We describe in detail the numerical method we use to reproduce the effect of a large parallel thermal conductivity, which makes magnetic field lines almost isothermal. We compare the results of the two simulations, showing that the anisotropic thermal conductivity causes the formation of a hot island when closed magnetic surfaces exist, while temperature becomes almost uniform when the magnetic field is chaotic. After a transient single-helicity state that is formed in the initial phase, a stationary state is reached where the RFP configuration exists in a multiple helicity state, even though the Hartmann number is below the threshold found in previous simulations for the formation of multiple helicity states.

The temperature evolution in a magnetohydrodynamics (MHD) simulation of a reversed-field pinch (RFP) is investigated including thermal conductivity. For numerical reasons, an isotropic thermal conductivity is used, even though in a RFP plasma the parallel conductivity is much larger than the perpendicular one so that magnetic field lines tend to become isothermal. The system shows alternating multiple helicity states and quasi-single helicity states. Single-helical-axis states are formed when the amplitude of the dominant mode is above a determined threshold, as observed in experiments. The relation between heat transport and magnetic field topology that is observed in RFP experiments cannot be found in the simulation, since thermal conductivity is independent of the magnetic field. This difficulty should be taken into account in the numerical investigation of the RFP dynamics. In this paper, the first description of the temperature evolution in a compressible MHD simulation of a RFP is given.

The term very far-advanced otosclerosis is proposed to indicate otosclerotic patients with both bone and air conduction thresholds nonmeasurable on a standard clinical audiometer (blank audiogram). Three of these patients have undergone stapedotomy with satisfactory results. This confirms that cochlear implantation is not the best treatment for all profoundly deaf patients at least with implants available today. Some of the patients with a blank audiogram are better off with exploratory tympanotomy and stapedotomy.

On the long term Parkinson Disease (PD) treatment is often complicated by the occurrence of motor fluctuations. To find out whether early treatment of PD with levodopa, dopaminoagonists or 1-deprenyl is associated with any difference in motor fluctuations occurrence, the Italian Parkinson Study Groups initiated a multicenter, randomized study. Since November 1988, 475 patients cequiring effective treatment for idiopathic PD have been randomized to receive levodopa, dopoamine agonists or deprenyl. After 2 months of therapy, all patients evaluated with the Unified Parkinson Disease Rating Scale showed a significant amelioration. Daily living activities were more impaired in patients treated with deprenyl. Study design is presented and first resuts are discussed.

The reversed field pinch is studied using numerical simulations of the compressible magnetohydrodynamics equations. Contrary to what has been done in previous works, the hypotheses of constant density and vanishing pressure are not used. Two cases are investigated. In the first case the pressure is derived from an adiabatic condition and in the second case the pressure equation includes heating terms due to resistivity and viscosity. The evolution of the reversal parameter and the production of single helicity or multiple helicity states are different in the two cases. The simulations show that the results are affected by compressibility and are very sensitive to hypotheses on heat production.

We simultaneously registered the left apexcardiogram together with the left intraventricular pressure curve immediately before and after ventricular angiography in order to evaluate whether the relation existing between apexcardiographic protodiastolic filling period duration (cR interval) and left ventricular mean diastolic pressure (LVMDP) was maintained even in the presence of sudden variations of LVMDP. Administration of contrast media resulted in a significant increase of LVMDP (from 11.8 to 23.9 mm Hg) and in a simultaneous decrease of the cR interval (from 108.5 to 71.0 msec) and noninvasive LVMDP calculated as 36-0.24* cR closely correlated with the invasive values both before and after angiography (overall correlation r = 0.94). Apexcardiography thus confirms to be the only highly reliable noninvasive technique which can be used by the clinical cardiologist to measure LVMDP and/or mean pulmonary capillary wedge pressure.

We mechanocardiographically evaluated 50 patients with acute myocardial infarction, invasively monitored by Swan-Ganz catheters, in order to assess if mechanocardiography could provide reliable hemodynamic informations. The last 25 subjects were also studied by pulsed Doppler echocardiography. Our results confirm the high precision of apexcardiography in assessing mean pulmonary capillary wedge pressure (r = 0.91) while Doppler echocardiography proved itself better than mechanocardiography in assessing cardiac output (r = 0.82 vs r = 0.78). Moreover, Doppler echocardiography allowed a good estimation of mean pulmonary artery pressure (r = 0.81) which cannot be assessed by other noninvasive methods. However, we could not find any clinically useful relationship between Doppler mitralic flow characteristics and mean pulmonary capillary wedge pressure. Therefore noninvasive methods could represent a valid alternative to right heart catheterization provided that an integrated Doppler echocardiographic and mechanocardiographic approach is used.

Twenty-one subjects who suffered a recent medium sized anterior myocardial infarction conditioning a mild congestive heart failure were randomly allocated to treatment with captopril (25 mg b.i.d., 10 pts) or placebo (11 pts). After 2 months of therapy the group on the active treatment showed a significant increase of apexcardiographic protodiastolic filling period duration reflecting a clear cut decrease of mean pulmonary capillary wedge pressure (from 14 +/- 2 to 7 +/- 3 mm Hg) while patients on placebo did not show any difference in respect to baseline. Neither treatment significantly modified the PEP/LVET ratio despite a significant increase of left ventricular ejection fraction in patients receiving captopril (from 37 +/- 4% to 43 +/- 5%). Cardiac response to ACE-inhibitors can thus be noninvasively monitored by apexcardiography.