Bi-Directional Energy Cascades and the Origin of Kinetic Alfv\'enic and Whistler Turbulence in the Solar Wind

The observed sub-proton scale turbulence spectrum in the solar wind raises the question of how that turbulence originates. Observations of keV energetic electrons during solar quite-time suggest them as possible source of free energy to drive the turbulence. Using particle-in-cell simulations, we explore how free energy in energetic electrons, released by an electron two-stream instability drives Weibel-like electromagnetic waves that excite wave-wave interactions. Consequently, both kinetic Alfv\'enic and whistler waves are excited that evolve through inverse and forward magnetic energy cascades.Comment: 12 pages, 5 figures, Submitted to Physical Review Letter

Boundaries in the Moyal plane

We study the oscillations of a scalar field on a noncommutative disc implementing the boundary as the limit case of an interaction with an appropriately chosen confining background. The space of quantum fluctuations of the field is finite dimensional and displays the rotational and parity symmetry of the disc. We perform a numerical evaluation of the (finite) Casimir energy and obtain similar results as for the fuzzy sphere and torus.Comment: 19 pages, 6 figures. Replaced by published versio

Magnon frequency renormalization by the electronic geometrical spin torque in itinerant magnets

We investigate non-adiabatic effects on the magnon frequency in an interacting system of localized spins and itinerant electrons. Including the lowest order corrections to the adiabatic dynamics in an analytically solvable model, applicable to simple ferromagnets like Fe, Co and Ni, we find that the magnon frequency is renormalized by a geometrical torque arising from the electronic spin Berry curvature. Comparison to exact numerical simulations reveals that our analytical solution captures essential low-energy features, and provides a mechanism for the magnon frequency hardening observed in recent first principles calculations for Fe, provided the geometrical torque is taken into account

High-frequency Alfven waves in multi-ion coronal plasma : observational implications

We investigate the effects of high-frequency (of order ion gyrofrequency) Alfvén and ion-cyclotron waves on ion emission lines by studying the dispersion of these waves in a multi-ion coronal plasma. For this purpose we solve the dispersion relation of the linearized multifluid and Vlasov equations in a magnetized multi-ion plasma with coronal abundances of heavy ions. We also calculate the dispersion relation using nonlinear one-dimensional hybrid kinetic simulations of the multi-ion plasma. When heavy ions are present the dispersion relation of parallel propagating Alfvén cyclotron waves exhibits the following branches (in the positive Ω − k quadrant): right-hand polarized nonresonant and left-hand polarized resonant branch for protons and each ion. We calculate the ratio of ion to proton velocities perpendicular to the direction of the magnetic field for each wave modes for typical coronal parameters and find strong enhancement of the heavy ion perpendicular fluid velocity compared with proton perpendicular fluid velocity. The linear multifluid cold plasma results agree with linear warm plasma Vlasov results and with the nonlinear hybrid simulation model results. In view of our findings we discuss how the observed nonthermal line broadening of minor ions in coronal holes may relate to the high-frequency wave motions

Electron scattering in isotonic chains as a probe of the proton shell structure of unstable nuclei

Electron scattering on unstable nuclei is planned in future facilities of the GSI and RIKEN upgrades. Motivated by this fact, we study theoretical predictions for elastic electron scattering in the N=82, N=50, and N=14 isotonic chains from very proton-deficient to very proton-rich isotones. We compute the scattering observables by performing Dirac partial-wave calculations. The charge density of the nucleus is obtained with a covariant nuclear mean-field model that accounts for the low-energy electromagnetic structure of the nucleon. For the discussion of the dependence of scattering observables at low-momentum transfer on the gross properties of the charge density, we fit Helm model distributions to the self-consistent mean-field densities. We find that the changes shown by the electric charge form factor along each isotonic chain are strongly correlated with the underlying proton shell structure of the isotones. We conclude that elastic electron scattering experiments in isotones can provide valuable information about the filling order and occupation of the single-particle levels of protons.Comment: 13 pages; 19 figure

Pairing Matrix Elements and Pairing Gaps with Bare, Effective and Induced Interactions

The dependence on the single-particle states of the pairing matrix elements of the Gogny force and of the bare low-momentum nucleon-nucleon potential $v_{low-k}$ is studied in the semiclassical approximation for the case of a typical finite, superfluid nucleus ($^{120}$Sn). It is found that the matrix elements of $v_{low-k}$ follow closely those of $v_{Gogny}$ on a wide range of energy values around the Fermi energy $e_F$, those associated with $v_{low-k}$ being less attractive. This result explains the fact that around $e_F$ the pairing gap $\Delta_{Gogny}$ associated with the Gogny interaction (and with a density of single-particle levels corresponding to an effective $k$-mass $m_k\approx 0.7 m$) is a factor of about 2 larger than $\Delta_{low-k}$,being in agreement with $\Delta_{exp}$= 1.4 MeV. The exchange of low-lying collective surface vibrations among pairs of nucleons moving in time-reversal states gives rise to an induced pairing interaction $v_{ind}$ peaked at $e_F$. The interaction $(v_{low-k}+ v_{ind})Z_{\omega}$ arising from the renormalization of the bare nucleon-nucleon potential and of the single-particle motion ($\omega-$mass and quasiparticle strength $Z_{\omega}$) due to the particle-vibration coupling leads to a value of the pairing gap at the Fermi energy $\Delta_{ren}$ which accounts for the experimental value

Deformidad vertebral y mielomeningocele: actitud terapéutica y resultados

Presentamos nuestra experiencia en el tratamiento quirúrgico de la deformidad vertebral relacionada con el mielomeningocele entre los años 1972 y 1995. En ese período un total de 48 pacientes fueron intervenidos. Se han evaluado las condiciones generales previas, el estado prequirúrgico, las diversas modalidades de instrumentación y el resultado de las mismas, así como el tipo y número de complicaciones. Durante el período posquirúrgico inmediato hemos encontrado un porcentaje de infecciones del 68%. Sin embargo, el resultado final, tanto del equilibrio pélvico como del vertebral conseguido, no estuvo influenciado significativamente por esta complicación. El tipo de patología, las complicaciones generales derivadas de la misma, el tiempo quirúrgico empleado y las pérdidas sanguíneas, son condiciones estrechamente relacionadas con el número de infecciones encontradas.We present our experience on the surgical treatment of myelomeningocelelinked vertebral deformity between 1972 and 1995. We evaluated the previous general condition, the presurgical status, the instrument modalities and their outcome, as well as the type and number of complications in a series of 48 patients. During the immediate postoperative period, we found a 68% infection rate. However, the end result for pelvic as well as vertebral balance was not influenced significantly by this complication. The number of infections found is closely linked to the specific pathology, the complications, duration of operation, and blood loss

Complicaciones sépticas de la osteosíntesis lumbosacra: Análisis de 23 casos

Entre 1987 y 1995 hemos intervenido 295 pacientes afectos de patología lumbosacra realizando en todos ellos una artrodesis instrumentada. Veintitrés pacientes tuvieron como complicación una infección profunda, lo que equivale a un 7,8%. El germen más frecuentemente aislado como responsable de la infección fue el Staphylococcus aureus resistente a la meticilina. La antibioterapia más veces utilizada fue una cefalosporina de 2.a generación. La infección se resolvió en 4 ocasiones bajo tratamiento médico; sin embargo, en 19 se procedió a limpieza quirúrgica de los tejidos dañados no siendo necesaria la retirada del material de osteosíntesis. En 9 ocasiones se practicó una 2.a reintervención, y en otros 4 una tercera. En nuestra serie, fue necesario reintervenir quirúrgicamente el 50% de los pacientes a los que se practicó una limpieza quirúrgica. Dado que la profilaxis antibiótica debe de cubrir los gérmenes prevalentes en cada unidad hospitalaria, de acuerdo con su patrón de resistencia, hubiera sido más adecuado el empleo de antibióticos glucopeptídicos.Between 1987 and 1995 we performed an instrumented arthrodesis on 295 patients with lumbosacral pathology and 23 patients (7.8%) had a serious infection. Methicillin-resistent Staphylococcus aureus was the most frequently isolated causal germs. Second generation Cephalosporin was the antibiotic administered the most. The infection was cured in 4 cases with medical treatment. However, in 19 patients surgical cleaning of the damaged tissue was required, although it was not necessary to remove the osteosynthesis material. In 9 cases a second operation was performed and a third in 4 others. In our series, 50% of the patients who required surgical cleaning underwent another operation. Due to the fact that prophylactic antibiotics should cover the germs prevalent in each hospital ward, according to the resistence patterns, the use of Glycopeptid antibiotics would have been more appropriate

First measurements of electron vorticity in the foreshock and solar wind

We describe the methodology used to set up and compute spatial derivatives of the electron moments using data acquired by the Plasma Electron And Current Experiment (PEACE) from the four Cluster spacecraft. The results are used to investigate electron vorticity in the foreshock. We find that much of the measured vorticity, under nominal conditions, appears to be caused by changes in the flow direction of the return (either reflected or leakage from the magnetosheath) and strahl electron populations as they couple to changes in the magnetic field orientation. This in turn results in deflections in the total bulk velocity producing the measured vorticity