Factors affecting color correction of retroreflective markings

A nighttime field study was conducted to assess the effects of retroreflective material area, distribution, and color on judgments of conspicuity. Participants, seated in a stationary vehicle, took part in a pairwise comparison of the stimuli. The independent variables included retroreflective power, area and distribution of the retroreflective material, color of the retroreflective material, participant age, and participant gender. The results indicate that color (white, fluorescent yellow-green, and fluorescent red-orange) was a significant factor in the judgment of conspicuity, as might be predicted from the Helmholtz-Kohlrausch effect. In addition, color interacted with the distribution of material at the high level of retroreflective power. The area of the retroreflective material was also significant. The present study, in agreement with a number of previous studies, indicates that color influences the conspicuity of retroreflective stimuli, but that the results are not always in agreement with color correction factors prescribed in ASTM E 1501. The discrepancy between empirically derived color correction factors seems to be attributable to an interaction of the stimulus size (subtended angle) and color, which previous studies have not extensively examined. To a lesser degree, the retroreflective power of a material also appears to influence conspicuity. While the ASTM correction factors may be appropriate for intermediate subtended solid angles, particularly for nonsaturated colors, smaller correction factors appear appropriate for markings subtending small angles (approaching point sources), and larger factors for larger subtended angles of saturated stimuli.The University of Michigan Industry Affiliation Program for Human Factors in Transportation Safetyhttp://deepblue.lib.umich.edu/bitstream/2027.42/91263/1/102869.pd

Just noticeable differences for low-beam headlamp intensities

A recent study by Huey, Dekker, and Lyons (1994) concluded that a difference between two signal lamp intensities of less than 25% cannot be detected reliably by most drivers. Consequently, Huey et al. recommended that an intensity difference of 25% be used as a criterion for inconsequential noncompliance with federal regulations for signal lamps. The present study was designed to evaluate just noticeable differences for glare intensities of oncoming low-beam headlamps. The results of this study indicate that, under controlled conditions, just noticeable differences in the low-beam headlighting context are between 11% and 19%. In real-world conditions, just noticeable differences would probably be somewhat larger. Therefore, the recommendation by Huey et al. of using 25% as a criterion for inconsequential noncompliance of signal lamps is also about right for low-beam headlamps, at least with respect to how headlamps themselves are perceived by other drivers (such as discomfort glare). The 25% value may also apply with respect to how headlamps affect the ability of drivers to see illuminated objects, but further research on that issue would be desirable.Michigan University, Ann Arbor, Industry Affiliation Program for Human Factors in Transportation Safetyhttp://deepblue.lib.umich.edu/bitstream/2027.42/49359/1/UMTRI-97-4.pd

The Evolution of Distorted Rotating Black Holes III: Initial Data

In this paper we study a new family of black hole initial data sets corresponding to distorted ``Kerr'' black holes with moderate rotation parameters, and distorted Schwarzschild black holes with even- and odd-parity radiation. These data sets build on the earlier rotating black holes of Bowen and York and the distorted Brill wave plus black hole data sets. We describe the construction of this large family of rotating black holes. We present a systematic study of important properties of these data sets, such as the size and shape of their apparent horizons, and the maximum amount of radiation that can leave the system during evolution. These data sets should be a very useful starting point for studying the evolution of highly dynamical black holes and can easily be extended to 3D.Comment: 16 page

Trapped Surfaces in Vacuum Spacetimes

An earlier construction by the authors of sequences of globally regular, asymptotically flat initial data for the Einstein vacuum equations containing trapped surfaces for large values of the parameter is extended, from the time symmetric case considered previously, to the case of maximal slices. The resulting theorem shows rigorously that there exists a large class of initial configurations for non-time symmetric pure gravitational waves satisfying the assumptions of the Penrose singularity theorem and so must have a singularity to the future.Comment: 14 page

Factors affecting tether use and misuse

This project investigated factors relating to tether use and misuse. Volunteer testing was performed with 37 subjects on 16 different vehicles using 2 forward-facing child restraints (Britax Marathon 70 or the Evenflo Triumph), with each subject performing 8 child restraint installations on a set of four vehicles. Vehicles were selected to provide a variety of general tether locations (filler panel, upper seatback, lower seatback, floor, or roof), as well as a variety of recommended tether routings with respect to the head restraint: under, over, around. Simple instruction regarding the LATCH system was provided after the fourth trial. Subjects used the tether in 89% of the 294 forward-facing trials and attached the tether correctly in 57% of installations. Subjects were more likely to use the tether if they were less than age 40, had previous tether experience, if the tether was located on a filler panel, and if the vehicle did not have any potentially confusing hardware. In addition, tether use was 83% in the first four trials and increased to 95% in the last four trials after instruction was provided. Subjects had the greatest difficulty in the pickup truck, which use loops of webbing as a router for the installed position and the tether anchor for the adjacent position; the tether was attached correctly in only 11 percent of installations. Tethers were more likely to be used when the tether anchor was located on the filler panel of sedans, which had a use rate of 95 percent, compared to when the anchor was located on the floor, roof, or seatback, which had use rates ranging from 79 to 89 percent. Tethers were less likely to be attached correctly when there was potentially confusing hardware present, 47 percent, compared to 70 percent. In addition, tether anchors located on the filler panel or mid seatback had higher rates of correct attachment, 60 and 69 percent , respectively, than those on the floor, roof, or lower seatback, which all had correct attachment rates lower than 50 percent . No vehicle tether hardware characteristics or vehicle manual directions were associated specifically with correct tether routing and head restraint position. Installations involving the single tether strap were 10 times as likely to have the tether attached correctly and 1.7 times as likely to be routed correctly and have the head restraint positioned correctly, compared with installations with the v-shaped tether. Lack of instruction in most vehicle owner’s manuals regarding the routing of a V-style tether more challenging to use. With the single strap-style tether, it was more straightforward to have the tether strap flat and pull it tight, as well as to route it as directed. With the V-style tether, the adjustment hardware was often located underneath or close to the head restraint when installed in the vehicle, making it difficult to tighten. Recommendations to reduce tether misuse include labeling tether anchors, eliminating confusing hardware, allowing any head restraint position (including removal), providing instruction for routing V-style tethers, allowing options in tether routing, and redesigning tether anchors/routers found in pickup trucks.Insurance Institute for Highway Safetyhttp://deepblue.lib.umich.edu/bitstream/2027.42/106031/1/102990.pd

Assessment of three Resistance-Nodulation-Cell Division drug efflux transporters of Burkholderia cenocepacia in intrinsic antibiotic resistance

<p>Abstract</p> <p>Background</p> <p><it>Burkholderia cenocepacia </it>are opportunistic Gram-negative bacteria that can cause chronic pulmonary infections in patients with cystic fibrosis. These bacteria demonstrate a high-level of intrinsic antibiotic resistance to most clinically useful antibiotics complicating treatment. We previously identified 14 genes encoding putative Resistance-Nodulation-Cell Division (RND) efflux pumps in the genome of <it>B. cenocepacia </it>J2315, but the contribution of these pumps to the intrinsic drug resistance of this bacterium remains unclear.</p> <p>Results</p> <p>To investigate the contribution of efflux pumps to intrinsic drug resistance of <it>B. cenocepacia </it>J2315, we deleted 3 operons encoding the putative RND transporters RND-1, RND-3, and RND-4 containing the genes <it>BCAS0591</it>-<it>BCAS0593</it>, <it>BCAL1674</it>-<it>BCAL1676</it>, and <it>BCAL2822</it>-<it>BCAL2820</it>. Each deletion included the genes encoding the RND transporter itself and those encoding predicted periplasmic proteins and outer membrane pores. In addition, the deletion of <it>rnd-3 </it>also included <it>BCAL1672</it>, encoding a putative TetR regulator. The <it>B. cenocepacia rnd-3 </it>and <it>rnd-4 </it>mutants demonstrated increased sensitivity to inhibitory compounds, suggesting an involvement of these proteins in drug resistance. Moreover, the <it>rnd-3 </it>and <it>rnd-4 </it>mutants demonstrated reduced accumulation of N-acyl homoserine lactones in the growth medium. In contrast, deletion of the <it>rnd-1 </it>operon had no detectable phenotypes under the conditions assayed.</p> <p>Conclusion</p> <p>Two of the three inactivated RND efflux pumps in <it>B. cenocepacia </it>J2315 contribute to the high level of intrinsic resistance of this strain to some antibiotics and other inhibitory compounds. Furthermore, these efflux systems also mediate accumulation in the growth medium of quorum sensing molecules that have been shown to contribute to infection. A systematic study of RND efflux systems in <it>B. cenocepacia </it>is required to provide a full picture of intrinsic antibiotic resistance in this opportunistic bacterium.</p