Ionization of Infalling Gas

H-alpha emission from neutral halo clouds probes the radiation and hydrodynamic conditions in the halo. Armed with such measurements, we can explore how radiation escapes from the Galactic plane and how infalling gas can survive a trip through the halo. The Wisconsin H-Alpha Mapper (WHAM) is one of the most sensitive instruments for detecting and mapping optical emission from the ISM. Here, we present recent results exploring the ionization of two infallling high-velocity complexes. First, we report on our progress mapping H-alpha emission covering the full extent of Complex A. Intensities are faint (<100 mR; EM <0.2 pc cm^-6 but correlate on the sky and in velocity with 21-cm emission. Second, we explore the ionized component of some Anti-Center Complex clouds studied by Peek et al. (2007) that show dynamic shaping from interaction with the Galactic halo.Comment: 4 pages, 2 figures; to appear in proceedings of "The Role of Disk-Halo Interaction in Galaxy Evolution: Outflow vs Infall?" held in Espinho, Portugal during 2008 Augus

Measurement of a 2D fast-ion velocity distribution function by tomographic inversion of fast-ion D-alpha spectra

We present the first measurement of a local fast-ion 2D velocity distribution function f(v||, v⊥). To this end, we heated a plasma in ASDEX Upgrade by neutral beam injection and measured spectra of fast-ion Dα (FIDA) light from the plasma centre in three views simultaneously. The measured spectra agree very well with synthetic spectra calculated from a TRANSP/NUBEAM simulation. Based on the measured FIDA spectra alone, we infer f(v||, v⊥) by tomographic inversion. Salient features of our measurement of f(v||, v⊥) agree reasonably well with the simulation: the measured as well as the simulated f(v||, v⊥) are lopsided towards negative velocities parallel to the magnetic field, and they have similar shapes. Further, the peaks in the simulation of f(v||, v⊥) at full and half injection energies of the neutral beam also appear in the measurement at similar velocity-space locations. We expect that we can measure spectra in up to seven views simultaneously in the next ASDEX Upgrade campaign which would further improve measurements of f(v||, v⊥) by tomographic inversion

Utilization and metabolism of palmityl and oleoyl fatty acids and alcohols in caecal enterocytes of Atlantic salmon (Salmo salar L.)

The substitution of fish oil with wax ester-rich calanoid copepod-derived oil in diets for carnivorous fish, such as Atlantic salmon, has previously indicated a lower lipid digestibility. This suggests that the fatty alcohols (FAlc) present in wax esters may be a poorer substrate for intestinal enzymes than the fatty acids (FA) in triacylglycerol, the major lipid in fish oil. The hypothesis tested was that the possible lower utilization of dietary FAlc by salmon enterocytes is at the level of uptake and that subsequent intracellular metabolism was identical to that of FA. A dual-labelled FAlc-FA metabolism assay was employed to determine simultaneous FAlc and FA uptake and relative utilisation in enterocytes isolated from pyloric caeca of Atlantic salmon fed either a diet supplemented with fish oil or wax ester-rich Calanus oil. The diets were fed for 10 weeks before caecal enterocytes from each dietary group were isolated and incubated with equimolar mixtures of either [1-14C]16:0 FA and [9,10(n)-3H]16:0 FAlc, or [1-14C]18:1n-9 FA and [9,10(n)-3H]18:1n-9 FAlc. Uptake was measured after 2 h with relative utilization of labelled FAlc and FA calculated as a percentage of uptake. Differences in uptake were observed, with FA showing higher uptake than FAlc, and 18:1 chains a higher uptake than 16:0. A proportion of unesterified FAlc was possibly recovered in the cells, but the majority of FALc was recovered in lipid classes such as triacylglycerol and phospholipids indicating substantial conversion of FAlc to FA followed by esterification. However, incorporation of FA and FAlc into esterified lipids was higher when derived from FA than from FAlc. Twenty-five to fifty percentage of the absorbed 16:0 FA was recovered in TAG fraction of the enterocytes compared with fifteen to seventy-five percentage of 18:1 FA. Twenty to thirty percentage of the absorbed 16:0 FA was recovered in the PC fraction of the enterocytes compared with only five to fifteen percentage of the 18:1 FA. Less than 15% of the fatty chains taken up by the cells was used for energy production, with significantly higher oxidation of 18:1 in enterocytes from fish fed the fish oil diet compared to the Calanus oil diet. However, overall, dietary copepod oil had little effect on FAlc and FA metabolism. Metabolic modification by elongation and/or desaturation was generally low at 1-5% of uptake. We conclude that our hypothesis was generally proved in that the uptake of FAlc by salmon enterocytes was lower than the uptake of FA and that subsequent intracellular metabolism of FAlc was similar to that of FA. However, unesterified FAlc was possibly recovered in the cells suggesting that the conversion to FA may not be concomitant with uptake

High-definition velocity-space tomography of fast-ion dynamics

Velocity-space tomography of the fast-ion distribution function in a fusion plasma is usually a photon-starved tomography method due to limited optical access and signal-to-noise ratio of fast-ion Dα (FIDA) spectroscopy as well as the strive for high-resolution images. In high-definition tomography, prior information makes up for this lack of data. We restrict the target velocity space through the measured absence of FIDA light, impose phase-space densities to be non-negative, and encode the known geometry of neutral beam injection (NBI) sources. We further use a numerical simulation as prior information to reconstruct where in velocity space the measurements and the simulation disagree. This alternative approach is demonstrated for four-view as well as for two-view FIDA measurements. The high-definition tomography tools allow us to study fast ions in sawtoothing plasmas and the formation of NBI peaks at full, half and one-third energy by time-resolved tomographic movies

Bianchi type I space and the stability of inflationary Friedmann-Robertson-Walker space

Stability analysis of the Bianchi type I universe in pure gravity theory is studied in details. We first derive the non-redundant field equation of the system by introducing the generalized Bianchi type I metric. This non-redundant equation reduces to the Friedmann equation in the isotropic limit. It is shown further that any unstable mode of the isotropic perturbation with respect to a de Sitter background is also unstable with respect to anisotropic perturbations. Implications to the choice of physical theories are discussed in details in this paper.Comment: 5 pages, some comment adde

Friedmann Equation and Stability of Inflationary Higher Derivative Gravity

Stability analysis on the De Sitter universe in pure gravity theory is known to be useful in many aspects. We first show how to complete the proof of an earlier argument based on a redundant field equation. It is shown further that the stability condition applies to $k \ne 0$ Friedmann-Robertson-Walker spaces based on the non-redundant Friedmann equation derived from a simple effective Lagrangian. We show how to derive this expression for the Friedmann equation of pure gravity theory. This expression is also generalized to include scalar field interactions.Comment: Revtex, 6 pages, Add two more references, some typos correcte

Deuterium temperature, drift velocity, and density measurements in non-Maxwellian plasmas at ASDEX Upgrade

We measure the deuterium density, the parallel drift velocity, and parallel and perpendicular temperatures (T∥, T⊥) in non-Maxwellian plasmas at ASDEX Upgrade. This is done by taking moments of the ion velocity distribution function measured by tomographic inversion of five simultaneously acquired spectra of Dα-light. Alternatively, we fit the spectra using a bi-Maxwellian distribution function. The measured kinetic temperatures (T∥ = 9 keV, T⊥ = 11 keV) reveal the anisotropy of the plasma and are substantially higher than the measured boron temperature (7 keV). The Maxwellian deuterium temperature computed with TRANSP (6 keV) is not uniquely measurable due to the fast ions. Nevertheless, simulated kinetic temperatures accounting for fast ions based on TRANSP (T∥= 8.3 keV, T⊥ = 10.4 keV) are in excellent agreement with the measurements. Similarly, the Maxwellian deuterium drift velocity computed with TRANSP (300 km s-1) is not uniquely measurable, but the simulated kinetic drift velocity accounting for fast ions agrees with the measurements (400 km s-1) and is substantially larger than the measured boron drift velocity (270 km s-1). We further find that ion cyclotron resonance heating elevates T∥ and T⊥ each by 2 keV without evidence for preferential heating in the Dα spectra. Lastly, we derive an expression for the 1D projection of an arbitrarily drifting bi-Maxwellian onto a diagnostic line-of-sight

Measurement of the top pair production cross section in 8 TeV proton-proton collisions using kinematic information in the lepton plus jets final state with ATLAS

A measurement is presented of the $t\bar{t}$ inclusive production cross-section in $pp$ collisions at a center-of-mass energy of $\sqrt{s}=8$ TeV using data collected by the ATLAS detector at the CERN Large Hadron Collider. The measurement was performed in the lepton+jets final state using a data set corresponding to an integrated luminosity of 20.3 fb$^{-1}$. The cross-section was obtained using a likelihood discriminant fit and $b$-jet identification was used to improve the signal-to-background ratio. The inclusive $t\bar{t}$ production cross-section was measured to be $260\pm 1{\textrm{(stat.)}} ^{+22}_{-23} {\textrm{(syst.)}}\pm 8{\textrm{(lumi.)}}\pm 4{\mathrm{(beam)}}$ pb assuming a top-quark mass of 172.5 GeV, in good agreement with the theoretical prediction of $253^{+13}_{-15}$ pb. The $t\bar{t}\to (e,\mu)+{\mathrm{jets}}$ production cross-section in the fiducial region determined by the detector acceptance is also reported.Comment: Published version, 19 pages plus author list (35 pages total), 3 figures, 2 tables, all figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2013-06