9,498 research outputs found

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

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    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

    Growth and Investigation of Nd_{1-x}Sm_{x}ScO_{3} and Sm_{1-x}Gd_{x}ScO_{3} Solid-Solution Single Crystals

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    The pseudo-cubic lattice parameters of rare-earth (RE) scandate, REScO3, single crystals grown by the Czochralski technique with RE=Dy to Pr lie between about 3.95 and 4.02 Angstrom. These crystals are the only available perovskite substrates in this lattice constant range that can withstand virtually any thin film growth conditions. Two members of this series, PmScO3 and EuScO3, are, however, not suitable for substrate applications. Because the pseudo-cubic lattice parameters between neighbouring REScO3 compounds decrease with rising atomic number of the RE in about 0.01 Angstrom steps, the unsuitability of PmScO3 (radioactivity) and EuScO3 (incompatibility with Si) causes an interruption in this lattice spacing sequence. To replace them, solid solutions of their adjacent rare-earth scandates, i.e., (Nd0.5Sm0.5)ScO3 and (Sm0.5Gd0.5)ScO3, were grown by the Czochralski method. Their average pseudo-cubic lattice parameters of 3.9979 Angstrom and 3.9784 Angstrom are very close to those of PmScO3 and EuScO3, respectively, and they show very low segregation. These qualities make these solid solutions excellent substitutes for PmScO3 and EuScO3.Comment: 16 pages, 6 figures, 6 table

    A COMPARISON OF HYPOTHETICAL PHONE AND MAIL CONTINGENT VALUATION RESPONSES FOR GREEN PRICING ELECTRICITY PROGRAMS

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    To date, much of the policy and research debate on contingent valuation mode effects has relied on experiences drawn from other research disciplines. This study provides the first contingent valuation phone-mail comparison that meets current standards for response rates, draws from a general population, is relevant to the valuation of general environmental goods, and allows comparisons with actual sign-ups. Consistent with previous research in other disciplines, social desirability bias is found in responses to subjective questions --thus leading to more environmentally favorable responses on the phone. However, this effect does not carry over to hypothetical participation decisions. Hypothetical bias is found in both modes. Yet, application of calibration methods using debriefing questions provided nearly identical values across modes. As such, neither mode appears to dominate from the perspective of providing more valid estimates of actual participation decisions. The selection of survey mode must be based on other criteria.Environmental Economics and Policy,

    Enhanced Detection of Emotional Facial Expressions in Borderline Personality Disorder

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    Background: Borderline personality disorder (BPD) is commonly proposed to be characterized by an enhanced sensitivity for emotional stimuli. In the present study, we investigated whether BPD patients show a superior detection of emotional facial expressions relative to healthy controls. The detection of emotional information in the environment represents an important facet of emotional sensitivity. Sampling and Methods: Twenty patients with BPD were compared with 25 healthy controls. The participants were presented a rapid, continuous stream of neutral and randomly inserted emotional facial expressions and were asked to report the presentation of an emotional facial stimulus after each trial. Availability of cognitive resources was manipulated via two different task demands. Results: The participants with BPD performed significantly better in the detection of positive and negative facial expressions compared to the healthy controls. False alarm rates did not differ significantly between the two groups. Conclusions: The BPD participants showed an enhanced detection of emotional expressions that might be related to the emotional disturbances they experience. In particular, we will discuss the role of this superior emotion detection (in combination with previously reported deficits in the labeling of emotional states) for the understanding of emotional instability in BPD

    The regional impact of Indonesia's fiscal policy on oil and gas: Options for reform

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    This paper analyzes the regional impact of Indonesia's fuel policy. It discusses how the sharing of oil and gas revenue and taxes on oil and gas between the center and the regions affect sub-national fiscal position and what the regional incidence of the fuel subsidies is. It also analyzes the regional impact of president's recent proposal to discontinue subsidizing vehicle fuel aswell as the proposal to eliminate the fuel subsidies altogether and shows how the regions are affected ty these suggestions

    Existence of axially symmetric static solutions of the Einstein-Vlasov system

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    We prove the existence of static, asymptotically flat non-vacuum spacetimes with axial symmetry where the matter is modeled as a collisionless gas. The axially symmetric solutions of the resulting Einstein-Vlasov system are obtained via the implicit function theorem by perturbing off a suitable spherically symmetric steady state of the Vlasov-Poisson system.Comment: 32 page

    Pion damping width from SU(2) x SU(2) NJL model

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    Within the framework of the NJL model, we investigate the modification of the pion damping width in a hot pion gas for temperatures ranging from 0 to 180 MeV. The pion is found to broaden noticeably at T > 60 MeV. Near the chiral phase transition T ~ 180 MeV, the pion width is saturated and amounts to 70 MeV. The main contribution to the width comes from pion-pion collisions. Other contributions are found negligibly small.Comment: LaTeX2e, 13 pages, 2 figure

    Scalar correlations in a quark plasma and low mass dilepton production

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    We investigate possible consequences of resonant scalar interactions for dilepton production from a quark plasma at the chiral phase transition. It is found that this production mechanism is strongly suppressed compared to the Born process and has no significance for present experiments.Comment: 7 pages revtex, 2 ps figure

    Three Types of Cooling Superfluid Neutron Stars: Theory and Observations

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    Cooling of neutron stars (NSs) with the cores composed of neutrons, protons, and electrons is simulated assuming 1^1S0_0 pairing of neutrons in the NS crust, and also 1^1S0_0 pairing of protons and weak 3^3P2_2 pairing of neutrons in the NS core, and using realistic density profiles of the superfluid critical temperatures Tc(ρ)T_{\rm c}(\rho). The theoretical cooling models of isolated middle-aged NSs can be divided into three main types. (I) {\it Low-mass}, {\it slowly cooling} NSs where the direct Urca process of neutrino emission is either forbidden or almost fully suppressed by the proton superfluidity. (II) {\it Medium-mass} NSs which show {\it moderate} cooling via the direct Urca process suppressed by the proton superfluidity. (III) {\it Massive} NSs which show {\it fast} cooling via the direct Urca process weakly suppressed by superfluidity. Confronting the theory with observations we treat RX J0822--43, PSR 1055--52 and RX J1856--3754 as slowly cooling NSs. To explain these sufficiently warm sources we need a density profile Tc(ρ)T_{\rm c}(\rho) in the crust with a rather high and flat maximum and sharp wings. We treat 1E 1207--52, RX J0002+62, PSR 0656+14, Vela, and Geminga as moderately cooling NSs. We can determine their masses for a given model of proton superfluidity, Tcp(ρ)T_{\rm cp}(\rho), and the equation of state in the NS core. No rapidly cooling NS has been observed so far.Comment: 12 pages, 10 figures, Astron. Astrophys., submitte
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