Ionization by bulk heating of electrons in capacitive radio frequency atmospheric pressure microplasmas

Electron heating and ionization dynamics in capacitively coupled radio frequency (RF) atmospheric pressure microplasmas operated in helium are investigated by Particle in Cell simulations and semi-analytical modeling. A strong heating of electrons and ionization in the plasma bulk due to high bulk electric fields are observed at distinct times within the RF period. Based on the model the electric field is identified to be a drift field caused by a low electrical conductivity due to the high electron-neutral collision frequency at atmospheric pressure. Thus, the ionization is mainly caused by ohmic heating in this "Omega-mode". The phase of strongest bulk electric field and ionization is affected by the driving voltage amplitude. At high amplitudes, the plasma density is high, so that the sheath impedance is comparable to the bulk resistance. Thus, voltage and current are about 45{\deg} out of phase and maximum ionization is observed during sheath expansion with local maxima at the sheath edges. At low driving voltages, the plasma density is low and the discharge becomes more resistive resulting in a smaller phase shift of about 4{\deg}. Thus, maximum ionization occurs later within the RF period with a maximum in the discharge center. Significant analogies to electronegative low pressure macroscopic discharges operated in the Drift-Ambipolar mode are found, where similar mechanisms induced by a high electronegativity instead of a high collision frequency have been identified

Pion scattering poles and chiral symmetry restoration

Using unitarized Chiral Perturbation Theory methods, we perform a detailed analysis of the $\pi\pi$ scattering poles $f_0(600)$ and $\rho(770)$ behaviour when medium effects such as temperature or density drive the system towards Chiral Symmetry Restoration. In the analysis of real poles below threshold, we show that it is crucial to extend properly the unitarized amplitudes so that they match the perturbative Adler zeros. Our results do not show threshold enhancement effects at finite temperature in the $f_0(600)$ channel, which remains as a pole of broad nature. We also implement T=0 finite density effects related to chiral symmetry restoration, by varying the pole position with the pion decay constant. Although this approach takes into account only a limited class of contributions, we reproduce the expected finite density restoration behaviour, which drives the poles towards the real axis, producing threshold enhancement and $\pi\pi$ bound states. We compare our results with several model approaches and discuss the experimental consequences, both in Relativistic Heavy Ion Collisions and in $\pi\to \pi\pi$ and $\gamma\to \pi\pi$ reactions in nuclei.Comment: 17 pages, 9 figures, final version to appear in Phys.Rev.D, added comments and reference

G93-1182 Best Management Practices for Agricultural Pesticides to Protect Water Resources

This NebGuide discusses what happens to pesticides after application, factors affecting pesticide movement, and best management practices to minimize the potential for pesticide contamination of ground and surface water. Users of pesticides and other agricultural chemicals must take appropriate precautions to reduce the risks of moving these materials into ground or surface water. The primary consideration should be whether the chemical is needed. If pesticides are needed, then the characteristics of the chemical, the sensitivity of the application site and the method of application should be considered

Prospective job analysis for the next pilot generation

To accomodate the expected growth of air traffic over the next two decades new operational concepts are currently under development, which will affect to some extent the job tasks and responsibilities of pilots and air traffic controllers. How will the operators perform in their potential new roles? Can we presume that they will easily be re‐trainable? Or will the job profile change to such an extent that it has to be considered already during the selection of the most suitable candidates? Especially for ab‐initio pilot and controller candidates selection decisions imply predictions of human performance for a longterm future. Therefore, a prospective analysis of job requirements is necessary to make sure that the selection battery is aligned with future roles and tasks. DLR has developed a simulation platform called AviaSim, which allows for low‐fidelity human‐in‐the‐loop simulations of potential future job tasks for pilots and controllers. Future scenarios are based on reviews of NextGen and SESAR concept papers and as well on “future workshops” with present job holders. In AviaSim we can examine the behavior of air traffic controllers working together in one scenario with up to eight pilots and additional experimental traffic. With eye‐gaze measurement, questionnaires and cognitive task interviews performance was analyzed in one en‐route and an arrival scenario. According to preliminarily findings future operators will need a higher degree of competence for operational monitoring, distributed teamwork, and time‐based operations. The simulation platform and the experimental setups are discussed in the paper

Searching for molecular outflows in Hyper-Luminous Infrared Galaxies

We present constraints on the molecular outflows in a sample of five Hyper-Luminous Infrared Galaxies using Herschel observations of the OH doublet at 119 {\mu}m. We have detected the OH doublet in three cases: one purely in emission and two purely in absorption. The observed emission profile has a significant blueshifted wing suggesting the possibility of tracing an outflow. Out of the two absorption profiles, one seems to be consistent with the systemic velocity while the other clearly indicates the presence of a molecular outflow whose maximum velocity is about ~1500 km/s. Our analysis shows that this system is in general agreement with previous results on Ultra-luminous Infrared Galaxies and QSOs, whose outflow velocities do not seem to correlate with stellar masses or starburst luminosities (star formation rates). Instead the galaxy outflow likely arises from an embedded AGN.Comment: Accepted for publication in MNRAS. 13 pages, 11 figures, 4 table