Neighborhood Crime and Travel Behavior: An Investigation of the Influence of Neighborhood Crime Rates on Mode Choice, MTI Report 07-02

While much attention has been given to the influence of urban form on travel behavior in recent years, little work has been done on how neighborhood crimes affect this dynamic. This research project studied seven San Francisco Bay Area cities, and found substantiation for the proposition that neighborhood crime rates have an influence on the propensity to choose non-automotive modes of transportation for home-based trips. Specifically, high vice and vagrancy crime rates were associated with a lowered probability of choosing transit in suburban cities for both work and non-work trips, high property crime rates were associated with a lower probability of walking for work trips in urban cities and inner-ring suburban cities, high violent crime rates with a lower probability of walking for work trips in suburban study cities, while higher property crime rates in San Francisco were associated with an increased probability of walking for non-work trips. While the signs of these significant relationships generally conformed to the author’s expectations—i.e., that high crime rates reduce the probability of choosing non-automotive modes of travel—the authors did not find statistically significant relationships for all city/trip model runs, suggesting that these relationships differ depending on the urban form and trip type contexts

Adaptive-wall wind-tunnel research at NASA-Ames Research Center

Adaptive wall wind tunnel research is summarized. Small scale two and three dimensional wind tunnel experiments and numerical experiments with a three dimensional adaptive wall simulator are included. A NACA 0012 airfoil was tested in a 25 by 13 cm slotted wall test section. Airflow through the test section walls was controlled by adjusting the pressures in segmented plenums. Interference free conditions were successfully attained in subsonic and transonic flows. For the three dimensional experiment, the 25 by 13 cm wind tunnel was modified to permit cross stream wall adjustments. The test model was a semispan wing mounted to one sidewall. Wall interference was substantially reduced at several angles of attack at Mach 0.60. A wing on wall configuration was also modeled in the numerical experiments. These flow simulations showed that free air conditions can be approximated by adjusting boundary conditions at only the floor and ceiling of the test section. No sidewall control was necessary. Typical results from these experiments are discussed

Diatom communities of travertine-precipitating springs on a gradient of anthropogenic disturbance in the Sandia Mountains, New Mexico

Carbonate-rich waters of travertine-precipitating springs facilitate unique physiochemical environments that support distinct diatom species assemblages adapted to the environmental stress of constant carbonate precipitation. Diatom communities in spring systems may be further limited by the impacts of historical and ongoing anthropogenic disturbance, which includes recreational activity and hydrologic modification of springs using spring boxes and wells. This study focused on impacts of water chemistry and anthropogenic disturbance on diatom assemblages found in travertine-precipitating springs. Data were collected in the fall of 2016 and spring of 2017 at eight spring sites, including six known to precipitate travertine, in the Sandia Mountains of central New Mexico. Water chemistry, benthic diatoms, sediment composition, percent organic matter, and categorical disturbance variables were analyzed. Hydrochemical analysis showed five of six springs known to precipitate travertine were actively forming travertine (saturation index of calcite near or greater than 1.00) during the fall sampling period. Diatom taxa observed in springs were indicative of active travertine precipitation (e.g., Diatoma mesodon, Halamphora montana), higher conductivities (e.g., Diploneis oblongella, Pinnularia spp.), and degree of hydrologic modifications to springs (e.g., Eucocconeis flexella, Gomphonema truncatum). Species richness was greater in non-travertine precipitating springs and diatom density varied among the springs, but was greater in springs during the spring sampling season. Diatom assemblage analysis, disturbance characterization, and other biological assessments can be used to prioritize restoration of springs with unique habitats, such as travertine-precipitating springs

OH Maser sources in W49N: probing differential anisotropic scattering with Zeeman pairs

Our analysis of a VLBA 12-hour synthesis observations of the OH masers in W49N has provided detailed high angular-resolution images of the maser sources, at 1612, 1665 and 1667 MHz. The images, of several dozens of spots, reveal anisotropic scatter broadening; with typical sizes of a few tens of milli-arc-seconds and axial ratios between 1.5 to 3. The image position angles oriented perpendicular to the galactic plane are interpreted in terms of elongation of electron-density irregularities parallel to the galactic plane, due to a similarly aligned local magnetic field. However, we find the apparent angular sizes on the average a factor of 2.5 less than those reported by Desai et al., indicating significantly less scattering than inferred earlier. The average position angle of the scattered broadened images is also seen to deviate significantly (by about 10 degrees) from that implied by the magnetic field in the Galactic plane. More intriguingly, for a few Zeeman pairs in our set, we find significant differences in the scatter broadened images for the two hands of polarization, even when apparent velocity separation is less than 0.1 km/s. Here we present the details of our observations and analysis, and discuss the interesting implications of our results for the intervening anisotropic magneto-ionic medium, as well as a comparison with the expectations based on earlier work.Comment: 5 pages, 3 figures, submitted to the Proceedings of the IAU Symposium 287: "Cosmic masers - from OH to H0

Positive equilibria of weakly reversible power law kinetic systems with linear independent interactions

In this paper, we extend our study of power law kinetic systems whose kinetic order vectors (which we call interactions) are reactant-determined (i.e. reactions with the same reactant complex have identical vectors) and are linear independent per linkage class. In particular, we consider PL-TLK systems, i.e. such whose T-matrix (the matrix with the interactions as columns indexed by the reactant complexes), when augmented with the rows of characteristic vectors of the linkage classes, has maximal column rank. Our main result states that any weakly reversible PL-TLK system has a complex balanced equilibrium. On the one hand, we consider this result as a Higher Deficiency Theorem for such systems since in our previous work, we derived analogues of the Deficiency Zero and the Deficiency One Theorems for mass action kinetics (MAK) systems for them, thus covering the Low Deficiency case. On the other hand, our result can also be viewed as a Weak Reversibility Theorem (WRT) in the sense that the statement any weakly reversible system with a kinetics from the given set has a positive equilibrium holds. According to the work of Deng et al. and more recently of Boros, such a WRT holds for MAK systems. However, we show that a WRT does not hold for two proper MAK supersets: the set PL-NIK of non-inhibitory power law kinetics (i.e. all kinetic orders are non-negative) and the set PL-FSK of factor span surjective power law kinetics (i.e. different reactants imply different interactions)