Novel sputtering-technology for grain-size control

In this paper, we present a description of a novel high-rate plasma sputtering system that allows the control of grain size in sputtered films. Additionally, the system has the advantage of a better utilization of the target material (around 80% to 90%) by eliminating the race track at the target as in conventional plasma magnetron sputtering systems. The potential and capabilities of this novel plasma sputtering device are demonstrated in this paper by the deposition of a number of different Cr thin films suitable for underlayers in thin-film media and for which we have performed a systematic X-ray and TEM analysis to determine the grain-size histograms, mean grain diameters, and their relationship to the sputtering processes

Infrared Spectroscopy of the Diffuse Ionized Halo of NGC 891

We present infrared spectroscopy from the Spitzer Space Telescope at one disk position and two positions at a height of 1 kpc from the disk in the edge-on spiral NGC 891, with the primary goal of studying halo ionization. Our main result is that the [Ne III]/[Ne II] ratio, which provides a measure of the hardness of the ionizing spectrum free from the major problems plaguing optical line ratios, is enhanced in the extraplanar pointings relative to the disk pointing. Using a 2D Monte Carlo-based photo-ionization code which accounts for the effects of radiation field hardening, we find that this trend cannot be reproduced by any plausible photo-ionization model, and that a secondary source of ionization must therefore operate in gaseous halos. We also present the first spectroscopic detections of extraplanar PAH features in an external normal galaxy. If they are in an exponential layer, very rough emission scale-heights of 330-530 pc are implied for the various features. Extinction may be non-negligible in the midplane and reduce these scale-heights significantly. There is little significant variation in the relative emission from the various features between disk and extraplanar environment. Only the 17.4 micron feature is significantly enhanced in the extraplanar gas compared to the other features, possibly indicating a preference for larger PAHs in the halo.Comment: 35 pages in ApJ preprint format, 8 figures, accepted for publication in ApJ. Minor change to Introduction to give appropriate credit to earlier, related wor

HALOGAS: HI Observations and Modeling of the Nearby Edge-on Spiral Galaxy NGC 4565

We present 21-cm observations and models of the neutral hydrogen in NGC 4565, a nearby, edge-on spiral galaxy, as part of the Westerbork Hydrogen Accretion in LOcal GAlaxieS (HALOGAS) survey. These models provide insight concerning both the morphology and kinematics of HI above, as well as within, the disk. NGC 4565 exhibits a distinctly warped and asymmetric disk with a flaring layer. Our modeling provides no evidence for a massive, extended HI halo. We see evidence for a bar and associated radial motions. Additionally, there are indications of radial motions within the disk, possibly associated with a ring of higher density. We see a substantial decrease in rotational velocity with height above the plane of the disk (a lag) of -40 +5/-20 km/s/kpc and -30 +5/-30 km s/kpc in the approaching and receding halves, respectively. This lag is only seen within the inner ~4.75' (14.9 kpc) on the approaching half and ~4.25' (13.4 kpc) on the receding, making this a radially shallowing lag, which is now seen in the HI layers of several galaxies. When comparing results for NGC 4565 and those for other galaxies, there are tentative indications of high star formation rate per unit area being associated with the presence of a halo. Finally, HI is found in two companion galaxies, one of which is clearly interacting with NGC 4565.Comment: 17 pages, 16 figures, accepted for publication in the Astrophysical Journal, modified affiliatio

Time-resolved imaging of non-diffusive carrier transport in long-lifetime halide perovskite thin films

Owing to their exceptional semiconducting properties, hybrid inorganic-organic perovskites show great promise as photovoltaic absorbers. In these materials, long-range diffusion of charge carriers allows for most of the photogenerated carriers to contribute to the photovoltaic efficiency. Here, time-resolved photoluminescence (PL) microscopy is used to directly probe ambipolar carrier diffusion and recombination kinetics in hybrid perovskites. This technique is applied to thin films of methylammonium lead tri-iodide MAPbI$_3$ obtained with two different fabrication routes, methylammonium lead tribromide (MAPbBr$_3$), and an alloy of formamidinium lead tri-iodide (FAPbI$_3$) and methylammonium lead bromide FA$_{0.85}$MA$_{0.15}$Pb(I$_{0.85}$Br_${0.15}$)$_3$. Average diffusion coefficients in the films leading to the highest device efficiencies and longest lifetimes, i.e., in FA$_{0.85}$MA$_{0.15}$Pb(I$_{0.85}$Br$_{0.15}$)$_3$ and acetonitrile-processed MAPbI$_3$, are found to be several orders of magnitude lower than in the other films. Further examination of the time-dependence shows strong evidence for non-diffusive transport. In particular, acetonitrile-processed MAPbI$_3$ shows distinct diffusion regimes on short and long timescales with an effective diffusion constant varying over 2 orders of magnitude. Our results also highlight the fact that increases in carrier lifetime in this class of materials are not necessarily concomitant with increased diffusion lengths and that the PL quantum efficiency under solar cell operating conditions is a greater indication of material, and ultimately device, quality

Self-thinning and Community Persistence in a Simple Size-structured Dynamical Model of Plant Growth

This paper presents a size-structured dynamical model of plant growth. The model takes the form of a partial differential-integral equation and includes the effects of self-shading by leaves. Closed form solutions are presented for the equilibrium size density distribution. Analytic conditions are derived for community persistence, and the self-thinning exponent is obtained as a function of species characteristics and environmental conditions

The relationship between hope and patient activation in consumers with schizophrenia: Results from longitudinal analyses

Hope (goal-directed thinking) and patient activation (knowledge and skills to manage one’s illness) are both important in managing chronic conditions like schizophrenia. The relationship between hope and patient activation has not been clearly defined. However, hope may be viewed as a foundational, motivating factor that can lead to greater involvement in care and feelings of efficacy. The purpose of the present study was to understand the prospective relationship between hope and patient activation in a sample of adults with schizophrenia (N=118). This study was a secondary data analysis from a study on Illness Management and Recovery (IMR) – a curriculum-based approach to schizophrenia self-management. Data were collected at baseline (prior to any intervention), and at 9 and 18-month follow-up. As predicted, hope and patient activation were significantly related with each other, showing large positive concurrent correlations. Demographics and background characteristics were not significantly related to patient activation or hope. Longitudinal analyses found no specific directional effect, yet suggested that hope and patient activation mutually influence each other over time. Our findings add flexibility in designing recovery-based interventions – fostering hope may not be a pre-requisite for activating consumers to be more involved in their own care

If cooperation is likely punish mildly: Insights from economic experiments based on the snowdrift game

Punishment may deter antisocial behavior. Yet to punish is costly, and the costs often do not offset the gains that are due to elevated levels of cooperation. However, the effectiveness of punishment depends not only on how costly it is, but also on the circumstances defining the social dilemma. Using the snowdrift game as the basis, we have conducted a series of economic experiments to determine whether severe punishment is more effective than mild punishment. We have observed that severe punishment is not necessarily more effective, even if the cost of punishment is identical in both cases. The benefits of severe punishment become evident only under extremely adverse conditions, when to cooperate is highly improbable in the absence of sanctions. If cooperation is likely, mild punishment is not less effective and leads to higher average payoffs, and is thus the much preferred alternative. Presented results suggest that the positive effects of punishment stem not only from imposed fines, but may also have a psychological background. Small fines can do wonders in motivating us to chose cooperation over defection, but without the paralyzing effect that may be brought about by large fines. The later should be utilized only when absolutely necessary.Comment: 15 pages, 6 figures; accepted for publication in PLoS ON

HALOGAS observations of NGC 5023 and UGC 2082: Modeling of non-cylindrically symmetric gas distributions in edge-on galaxies

In recent years it has become clear that the vertical structure of disk galaxies is a key ingredient for understanding galaxy evolution. In particular, the presence and structure of extra-planar gas has been a focus of research. The Hydrogen Accretion in LOcal GAlaxieS (HALOGAS) survey aims to provide a census on the rate of cold neutral gas accretion in nearby galaxies as well as a statistically significant set of galaxies that can be investigated for their extra-planar gas properties. In order to better understand the the vertical structure of the neutral hydrogen in the two edge-on HALOGAS galaxies NGC 5023 and UGC 2082 we construct detailed tilted ring models. The addition of distortions resembling arcs or spiral arms significantly improves the fit of the models to these galaxies. In the case of UGC 2082 no vertical gradient in rotational velocity is required in either symmetric models nor non-symmetric models to match the observations. The best fitting model features two arcs of large vertical extent that may be due to accretion. In the case of NGC 5023 a vertical gradient is required in symmetric models (dV/dz =$-14.9\pm3.8$ km s$^{-1}$ kpc$^{-1}$) and its magnitude is significantly lowered when non-symmetric models are considered (dV/dz =$-9.4\pm3.8$ km s$^{-1}$ kpc$^{-1}$). Additionally it is shown that the underlying disk of NGC 5023 can be made symmetric, in all parameters except the warp, in non-symmetric models. In comparison to the "classical" modeling these models fit the data significantly better with a limited addition of free parameters.Comment: 27 Pages, 22 Figures. Accepted for publication in MNRA