Kinematics of diffuse ionized gas in the disk halo interface of NGC 891 from Fabry-P\'erot observations

The properties of the gas in halos of galaxies constrain global models of the interstellar medium. Kinematical information is of particular interest since it is a clue to the origin of the gas. Here we report observations of the kinematics of the thick layer of the diffuse ionized gas in NGC 891 in order to determine the rotation curve of the halo gas. We have obtained a Fabry-P\'erot data cube in Halpha to measure the kinematics of the halo gas with angular resolution much higher than obtained from HI 21 cm observations. The data cube was obtained with the TAURUS II spectrograph at the WHT on La Palma. The velocity information of the diffuse ionized gas extracted from the data cube is compared to model distributions to constrain the distribution of the gas and in particular the halo rotation curve. The best fit model has a central attenuation tau_H-alpha=6, a dust scale length of 8.1 kpc, an ionized gas scale length of 5.0 kpc. Above the plane the rotation curve lags with a vertical gradient of -18.8 km/s/kpc. We find that the scale length of the H-alpha must be between 2.5 and 6.5 kpc. Furthermore we find evidence that the rotation curve above the plane rises less steeply than in the plane. This is all in agreement with the velocities measured in the HI.Comment: A&A, in press. 13 pages, 19 figure

Memento Mori: The development and validation of the Death Reflection Scale

Despite its potential for advancing organizational behavior (OB) research, the topic of death awareness has been vastly understudied. Moreover, research on death awareness has predominantly focused on the anxiety‐provoking aspect of death‐related cognitions, thus overlooking the positive aspect of death awareness, death reflection. This gap is exacerbated by the lack of a valid research instrument to measure death reflection. To address this issue, we offer a systematic conceptualization of death reflection, develop the Death Reflection Scale, and assess its psychometric properties across four studies. Further, using a sample of 268 firefighters, we examine whether death reflection buffers the detrimental impact of mortality cues at work on employee well‐being and safety performance. Results provide strong support for the psychometric properties of the Death Reflection Scale. Further, moderation analysis indicates death reflection weakens the negative effect of mortality cues on firefighters' safety performance. Overall, these findings suggest the newly developed Death Reflection Scale will prove useful in future research on death‐related cognitions

Time-of-flight Emission Profiles of the Entire Plume Using Fast Imaging During Pulsed Laser Deposition of YBa\u3csub\u3e2\u3c/sub\u3eCu\u3csub\u3e3\u3c/sub\u3eO\u3csub\u3e7−x\u3c/sub\u3e

Emission time-of-flight (TOF) profiles have been obtained using gated imagery to further the process control during the pulsed laser deposition of the high temperature superconductor, YBa2Cu3O7−x⁠. An intensified charge coupled device array was used to obtain a sequence of plume images at 10ns temporal resolution and 0.2mm spatial resolution. Plume imagery is transformed to TOF profiles and pulse-to-pulse variations removed using physically based smoothing techniques. Comparison with non-imaging sensors establishes excellent agreement, with systematic uncertainties in streaming speed and temperatures of less than 15% and 8%, respectively. The resulting streaming speeds of 0.4–1.2×106 cm/s and characteristic temperatures of 20000–200000K are characterized across the full plume. This new imaging TOF technique enables the monitoring of the complete evolution of speed distributions. Indeed, significant deviations from the forward-directed Maxwellian speed distributions are observed

The Origin of the Dust Arch in the Halo of NGC 4631: An Expanding Superbubble?

We study the nature and the origin of the dust arch in the halo of the edge-on galaxy NGC 4631 detected by Neininger & Dumke (1999). We present CO observations made using the new On-The-Fly mapping mode with the FCRAO 14m telescope, and find no evidence for CO emission associated with the dust arch. Our examination of previously published HI data shows that if previous assumptions about the dust temperature and gas/dust ratio are correct, then there must be molecular gas associated with the arch, below our detection threshold. If this is true, then the molecular mass associated with the dust arch is between 1.5 x 10^8 M(sun)and 9.7 x 10^8 M(sun), and likely towards the low end of the range. A consequence of this is that the maximum allowed value for the CO-to-H_2 conversion factor is 6.5 times the Galactic value, but most likely closer to the Galactic value. The kinematics of the HI apparently associated with the dust arch reveal that the gas here is not part of an expanding shell or outflow, but is instead two separate features (a tidal arm and a plume of HI sticking out into the halo) which are seen projected together and appear as a shell. Thus there is no connection between the dust "arch" and the hot X-ray emitting gas that appears to surround the galaxy Wang et al. (2001).Comment: 14 pages, including 4 figures. Accepted by A.J. for March 200

Integral Field Unit Observations of NGC 891: Kinematics of the Diffuse Ionized Gas Halo

We present high and moderate spectral resolution spectroscopy of diffuse ionized gas (DIG) emission in the halo of NGC 891. The data were obtained with the SparsePak integral field unit at the WIYN Observatory. The wavelength coverage includes the [NII]6548,6583, Halpha, and [SII]6716,6731 emission lines. Position-velocity (PV) diagrams, constructed using spectra extracted from four SparsePak pointings in the halo, are used to examine the kinematics of the DIG. Using two independent methods, a vertical gradient in azimuthal velocity is found to be present in the northeast quadrant of the halo, with magnitude approximately 15-18 km/s/kpc, in agreement with results from HI observations. The kinematics of the DIG suggest that this gradient begins at approximately 1 kpc above the midplane. In another part of the halo, the southeast quadrant, the kinematics are markedly different, and suggest rotation at about 175 km/s, much slower than the disk but with no vertical gradient. We utilize an entirely ballistic model of disk-halo flow in an attempt to reproduce the kinematics observed in the northeast quadrant. Analysis shows that the velocity gradient predicted by the ballistic model is far too shallow. Based on intensity cuts made parallel to the major axis in the ballistic model and an Halpha image of NGC 891 from the literature, we conclude that the DIG halo is much more centrally concentrated than the model, suggesting that hydrodynamics dominate over ballistic motion in shaping the density structure of the halo. Velocity dispersion measurements along the minor axis of NGC 891 seem to indicate a lack of radial motions in the halo, but the uncertainties do not allow us to set firm limits.Comment: 31 pages, 10 figures. Accepted for publication in the Astrophysical Journa

Semitransparent organic photovoltaic cells

We demonstrate semitransparent, small molecular weight organic solar cells employing a thin silver/indium tin oxide compound cathode with a maximum transmission of (60±6)%(60±6)% averaged over the visible spectral range and with a power conversion efficiency, ηp = (0.28±0.03)%ηp=(0.28±0.03)% under simulated, AM1.5G, 1 sun illumination. By increasing the Ag thickness, an average transmission of (26±3)%(26±3)% is achieved with ηp = (0.62±0.06)%ηp=(0.62±0.06)%, a value approximately half of that obtained for the same structure employing a conventional, reflective, and thick Ag cathode. A semitransparent tandem organic solar cell with ηp = (0.48±0.02)%ηp=(0.48±0.02)% and an average transmission of (44±4)%(44±4)% is also demonstrated. Semitransparent organic photovoltaic cells have potential uses as tinted and power-generating thin-film coatings on architectural surfaces, such as windows and walls. The use of a transparent top electrode also significantly simplifies the design of tandem cells, relaxing requirements for the placement of different absorbing materials at the maxima of optical fields introduced by reflective cathodes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87783/2/233502_1.pd

Direct glass bonded high specific power silicon solar cells for space applications

A lightweight, radiation hard, high performance, ultra-thin silicon solar cell is described that incorporates light trapping and a cover glass as an integral part of the device. The manufacturing feasibility of high specific power, radiation insensitive, thin silicon solar cells was demonstrated experimentally and with a model. Ultra-thin, light trapping structures were fabricated and the light trapping demonstrated experimentally. The design uses a micro-machined, grooved back surface to increase the optical path length by a factor of 20. This silicon solar cell will be highly tolerant to radiation because the base width is less than 25 microns making it insensitive to reduction in minority carrier lifetime. Since the silicon is bonded without silicone adhesives, this solar cell will also be insensitive to UV degradation. These solar cells are designed as a form, fit, and function replacement for existing state of the art silicon solar cells with the effect of simultaneously increasing specific power, power/area, and power supply life. Using a 3-mil thick cover glass and a 0.3 g/sq cm supporting Al honeycomb, a specific power for the solar cell plus cover glass and honeycomb of 80.2 W/Kg is projected. The development of this technology can result in a revolutionary improvement in high survivability silicon solar cell products for space with the potential to displace all existing solar cell technologies for single junction space applications