[en] Many foals are suffering from respiratory diseases during their first months of live. Pneumonia is the most important of these diseases. Thoracic radiography improves the diagnosis of foals respiratory diseases markedly. Within 4 years the thorax of 76 foals were examined radiologically. Pneumonia were diagnosed in 53 foals (69,7 %), there was the alveolar pattern (7 cases), the interstitial pattern (30) and the mixed alveolar-interstitial pattern (10). Further diagnoses were bronchopneumonia (11), aspiration pneumonia (5), lung abscesse (5) and hydrothorax (2). Thoracic radiography is a fast, non-invasive method of investigation, even applicable in very severely affected foals

[en] Innershell photoionization of atomic gases and vapors by soft x rays from a laser-produced plasma is a potential method for making lasers at short wavelengths. Normally, in such experiments only a single plasma spot or plasma line is created for the excitation. This gives high excitation rates but only a short excitation length. At high excitation rates detrimental influences, such as amplified spontaneous emission, optical saturation, or quenching processes, may decrease or even destroy a possible inversion. Therefore, it seems to be more favorable to use a number of separated plasma spots with smaller excitation rates and larger excitation lengths. As a test, a three-plasma spot device was constructed and used in the well-known Cd-photoionization laser at 442 nm. With a 600-mJ Nd:YAH laser (pulse length, 8 ns) for plasma production, output energies up to 300 μJ have been measured, which is more than a doubling of so far obtained data. On innershell excitation, levels may be populated that allow direct lasers as in the case of Cd or that are metastable and cannot be directly coupled to lower levels. In this case modifications in the excitation process are necessary. Such modifications may be an optical pump process in the atom prior to the innershell photoionization or an optical pump process (population transfer process) after the innershell ionization, leading to Raman or anti-Stokes Raman-type laser emissions. With these techniques and the developed multiplasma spot excitation device a variety of new laser emissions in K and Cs ions have been achieved which are indicated in the level schemes

[en] In 12 horses chronic interstitial lung disease was diagnosed. All horses were referrred because of unexplained loss of performance. In general there was no history of respiratory problems; 4 horses showed nasal discharge and 2 horses coughed. Results of arterial bloodgas analysis, tracheobronchial mucus cytology and radiological examination of the lungs were found in a typical combination, and they were different from results found generally in horses suffering from chronic obstructive pulmonary disease. Mean value of arterial partial pressure of oxygen was 100,6 mm Hg, arterial partial pressure of carbon dioxide was 45,1 mm Hg and alveolo-arterial difference in oxygen 5,1 mm Hg, respectively. In tracheobronchial aspirates pulmonary alveolar macrophages and neutrophil granulocytes were found in a relation of 2,6 : 1. Chest radiographs of all horses showed diffuse interstitial pattern throughout the lung

[en] The thermalization of relativistically flowing colliding plasmas is not well understood. The transition layer, in which both plasmas interact and thermalize, is wide and highly structured and the instabilities in this layer may yield non-thermal particle distributions and shock-less energy dissipation. The objective in this work is to explore the ability of an electron two-stream instability for thermalizing a plasma beam that moves at the mildly relativistic speed 0.3c through weakly magnetized plasma and to identify the resulting particle distributions. It is demonstrated here with particle-in-cell simulations that the electron two-stream instability leads to waves that propagate within a wide angular range relative to the flow velocity. The waves are thus not planar, as required for efficient electron surfing acceleration (ESA). The short lifetime of the waves implies, however, only weak modifications of the ESA by the oblique modes, since the waves are sufficiently homogeneous. The ion (proton) beams are not modulated, which would be required to extract some of their energy. The instability can thus heat the electrons significantly, but it fails to accelerate them to relativistic energies and it cannot form a shock layer by thermalizing the protons, at least not for the system and the resolved timescales considered here

[en] The filamentation instability of counterpropagating symmetric beams of electrons is examined with 1D and 2D particle-in-cell simulations, which are oriented orthogonally to the beam velocity vector. The beams are uniform, warm and their relative speed is mildly relativistic. The dynamics of the filaments is examined in 2D and it is confirmed that their characteristic size increases linearly in time. Currents orthogonal to the beam velocity vector are driven through the magnetic and electric fields in the simulation plane. The fields are tied to the filament boundaries and the scale size of the flow aligned and the perpendicular currents are thus equal. It is confirmed that the electrostatic and the magnetic forces are equally important, when the filamentation instability saturates in 1D. Their balance is apparently the saturation mechanism of the filamentation instability for our initial conditions. The electric force is relatively weaker but not negligible in the 2D simulation, where the electron temperature is set higher to reduce the computational cost. The magnetic pressure gradient is the principal source of the electrostatic field, when and after the instability saturates in the 1D simulation and in the 2D simulation.

[en] We present analytical and numerical studies of the dynamics of relativistic electron and ion holes in a collisionless plasma. Electromagnetic radiation can be trapped in relativistic electron phase-space holes mainly due to the relativistic mass increase of the electrons that are accelerated by the potential of the phase-space hole and by the quivering component of the electromagnetic field. Relativistic ion holes may exist in plasmas where the electrons are thermalized to extremely ultra-relativistic energies. They may be responsible for the acceleration of particles to GeV energies in active galactic nuclei and supernova remnant shocks. The analytic solutions are employed as initial conditions for numerical simulations in which the dynamics and stability of the phase-space holes are investigated. The results have relevance for intense laser-plasma experiments and for astrophysical plasmas

[en] A two-dimensional particle simulation models the collision of two electron-ion plasma clouds along a quasiparallel magnetic field. The collision speed is 0.9c and the density ratio, 10. A current sheet forms at the front of the dense cloud, in which the electrons and the magnetic field reach energy equipartition with the ions. A structure composed of a solenoidal and a toroidal magnetic field grows in this sheet. It resembles the cross-section of the torus of a spheromak, which may provide the coherent magnetic fields in gamma-ray burst jets needed for their prompt emissions.

[en] The impact of a flow-aligned and spatially homogeneous magnetic field on the filamentation instability (FI) is examined in a system of two equal counterstreaming non-relativistic cool electron beams. Particle-in-cell simulations that represent the plane perpendicular to the flow velocity vector confirm the reduction of the linear growth rate by the initial magnetic field. The FI is, however, not inhibited by a magnetic field with the critical strength, for which the solution of the linear dispersion relation predicts a full suppression. The saturation of the electromagnetic fields in the plasma involves a balance between the magnetic pressure gradient and the electric field resulting from the charge displacement. The simulations demonstrate that the magnetic energy gain and the field structure upon saturation do not depend on the initial magnetic field strength. This can be explained by the qualitative similarity of the spectrum of unstable wavenumbers, at least for subcritical strengths of the background magnetic field, and by the vanishing of the pressure gradient of a spatially homogeneous magnetic field. Magnetic trapping is apparently not the saturation mechanism for the considered plasma parameters. The spatial power spectrum of the saturated magnetic fields in the simulation plane can be approximated by a power-law function and the magnetic and electric spectra are similar at high wavenumbers. The final electron velocity distributions are comparable for all magnetic field strengths

[en] We present a numerical study of the surfing mechanism in which electrons are trapped in Bernstein-Greene-Kruskal (BGK) modes, and are accelerated across the magnetic field direction by the Lorentz force in magnetized space plasmas. The BGK modes are the product of an ion-beam Buneman instability that excites large-amplitude electrostatic upper-hybrid waves in the plasma. Our study, which is performed with particle-in-cell (PIC) and Vlasov codes, reveals the stability of the BGK mode as a function of the magnetic field strength and the ion beam speed. It is found that the surfing acceleration is more effective for a weaker magnetic field owing to the longer lifetime of the BGK modes. The importance of our investigation to electron acceleration in astrophysical environments has been emphasized

[en] An instability driven by the thermal anisotropy of a single electron species is investigated in a 2D particle-in-cell (PIC) simulation. This instability is the one considered by Weibel and it differs from the beam driven filamentation instability. A comparison of the simulation results with analytic theory provides similar exponential growth rates of the magnetic field during the linear growth phase of the instability. We observe, in accordance with previous works, the growth of electric fields during the saturation phase of the instability. Some components of this electric field are not accounted for by the linearized theory. A single-fluid-based theory is used to determine the source of this non-linear electric field. It is demonstrated that the magnetic stress tensor, which vanishes in a 1D geometry, is more important in this two-dimensional model used here. The electric field grows to an amplitude, which yields a force on the electrons that is comparable to the magnetic one. The peak energy density of each magnetic field component in the simulation plane agrees with previous estimates. Eddy currents develop, which let the amplitude of the third magnetic field component grow, which is not observed in a 1D simulation.