2,503 research outputs found
Why We Demolish: Assessing Heritage Loss in Philadelphia as a Catalyst for Policy Innovation in Historic Preservation
Demolition of listed historic resources through policy provisions such as economic hardship and public interest has, in recent years, led to increased controversy and tension in the preservation community. As approvals to demolish such heritage anchors as the Sidney Hillman Medical Center, the Church of the Assumption, the Levy-Leas Mansion, the Episcopal Cathedral\u27s Parish House, and the Boyd Theater interior continue to place the Philadelphia Historical Commission and developers at odds with preservation advocates, it is important to review the policy documents at the core of the issue. This thesis proposes that it is not the Commission but the policies that are complicating the Commission\u27s ability to best protect heritage assets. By examining how and why historically designated properties are demolished in Philadelphia (through a review of policy precedents and local case studies), this work proposes policy recommendations to stimulate innovation in preservation and reduce prolonged demolition cases in the future
Surrogate measures: A proposed alternative in human factors assessment of operational measures of performance
Surrogate measures are proposed as an alternative to direct assessment of operational performance for purposes of screening agents who may have to work under unusual stresses or in exotic environments. Such measures are particularly proposed when the surrogate can be empirically validated against the operational criterion. The focus is on cognitive (or throughput) performances in humans as opposed to sensory (input) or motor (output) measures, but the methods should be applicable for development of batteries which will tap input/output functions. A menu of performance tasks is under development for implementation on a battery-operated portable microcomputer, with 21 tests currently available. The tasks are reliable and become stable in minimum amounts of time; appear sensitive to some agents; comprise constructs related to actual job tasks; and are easily administered in most environments. Implications for human factors engineering studies in environmental stress are discussed
Fragmentation Phase Transition in Atomic Clusters II - Coulomb Explosion of Metal Clusters -
We discuss the role and the treatment of polarization effects in many-body
systems of charged conducting clusters and apply this to the statistical
fragmentation of Na-clusters. We see a first order microcanonical phase
transition in the fragmentation of for Z=0 to 8. We can
distinguish two fragmentation phases, namely evaporation of large particles
from a large residue and a complete decay into small fragments only. Charging
the cluster shifts the transition to lower excitation energies and forces the
transition to disappear for charges higher than Z=8. At very high charges the
fragmentation phase transition no longer occurs because the cluster
Coulomb-explodes into small fragments even at excitation energy .Comment: 19 text pages +18 *.eps figures, my e-mail adress: [email protected]
submitted to Z. Phys.
Effective two-body approach to the hierarchical three-body problem
The motion of three bodies can be solved perturbatively when a tightly bound inner binary is orbited by a distant perturber, giving rise, for example, to the well-known Kozai-Lidov oscillations. We propose to study the relativistic hierarchical three-body orbits by adapting the effective field theory techniques used in the two-body problem. This allows us to conveniently treat the inner binary as an effective point particle, thus reducing the complexity of the three-body problem to a simpler spinning two-body motion. We present in detail the mapping between the inner binary osculating elements and the resulting spin of the effective point particle. Our study builds towards a derivation of three-body analytic waveforms.The motion of three bodies can be solved perturbatively when a tightly bound inner binary is orbited by a distant perturber, giving rise, for example, to the well-known Kozai-Lidov oscillations. We propose to study the relativistic hierarchical three-body orbits by adapting the effective field theory techniques used in the two-body problem. This allows us to conveniently treat the inner binary as an effective point particle, thus reducing the complexity of the three-body problem to a simpler spinning two-body motion. We present in detail the mapping between the inner binary osculating elements and the resulting spin of the effective point particle. Our study builds towards a derivation of three-body analytic waveforms
Washington County Asset Map and Needs Assessment : Building a Network to Serve Youths at Risk for Serious Mental Illness
This study is the first in a series of planned investigations into pathways to care for adolescents and young adults with serious mental illness in Washington County. Resources were identified that may support a network for identifying and accessing services. Over 120 agencies were categorized into one of seven types: education, mental health, health, substance use / recovery, community / library, and law enforcement. Web-based information was collected for 85 of these agencies and representatives of 47 of these agencies were interviewed about challenges, collaborations, and ideas for solutions. We found a great deal of collaboration among agencies within different service sectors. For example, there is regular collaboration among health agencies, among educational agencies, and among agencies serving children and families. We identified networks that support the LGBTQ+ community as well as victims of domestic violence. Three agencies stood out with number and type of collaborations regarding youth and mental illness: Healthy Acadia, the Community Caring Collaborative, and the Aroostook Mental Health Center. We collated information about types of obstacles into these categories by frequency of mention: Lack of Services / Providers, Stigma / Community Culture, Transportation / Distance, Information Shortage, Cost, and Mistrust of Providers. Five areas of ideas from interviewees to address these challenges are provided. We end this report by highlighting some national, state, county, and local efforts to address these challenges as well as next steps for our research team
The Local Leo Cold Cloud and New Limits on a Local Hot Bubble
We present a multi-wavelength study of the local Leo cold cloud (LLCC), a
very nearby, very cold cloud in the interstellar medium. Through stellar
absorption studies we find that the LLCC is between 11.3 pc and 24.3 pc away,
making it the closest known cold neutral medium cloud and well within the
boundaries of the local cavity. Observations of the cloud in the 21-cm HI line
reveal that the LLCC is very cold, with temperatures ranging from 15 K to 30 K,
and is best fit with a model composed of two colliding components. The cloud
has associated 100 micron thermal dust emission, pointing to a somewhat low
dust-to-gas ratio of 48 x 10^-22 MJy sr^-1 cm^2. We find that the LLCC is too
far away to be generated by the collision among the nearby complex of local
interstellar clouds, but that the small relative velocities indicate that the
LLCC is somehow related to these clouds. We use the LLCC to conduct a shadowing
experiment in 1/4 keV X-rays, allowing us to differentiate between different
possible origins for the observed soft X-ray background. We find that a local
hot bubble model alone cannot account for the low-latitude soft X-ray
background, but that isotropic emission from solar wind charge exchange does
reproduce our data. In a combined local hot bubble and solar wind charge
exchange scenario, we rule out emission from a local hot bubble with an 1/4 keV
emissivity greater than 1.1 Snowdens / pc at 3 sigma, 4 times lower than
previous estimates. This result dramatically changes our perspective on our
local interstellar medium.Comment: 13 pages, 12 figures. Accepted for publication in the Astrophysical
Journal. Vector figure version available at
http://www.astro.columbia.edu/~jpeek
Crackling Noise, Power Spectra and Disorder Induced Critical Scaling
Crackling noise is observed in many disordered non-equilibrium systems in
response to slowly changing external conditions. Examples range from Barkhausen
noise in magnets to acoustic emission in martensites to earthquakes. Using the
non-equilibrium random field Ising model, we derive universal scaling
predictions for the dependence of the associated power spectra on the disorder
and field sweep rate, near an underlying disorder-induced non-equilibrium
critical point. Our theory applies to certain systems in which the crackling
noise results from avalanche-like response to a (slowly) increasing external
driving force, and is characterized by a broad power law scaling regime of the
power spectra. We compute the critical exponents and discuss the relevance of
the results to experiments.Comment: 27 Latex Pages, 14 eps figure
Spatial and temporal characterization of a Bessel beam produced using a conical mirror
We experimentally analyze a Bessel beam produced with a conical mirror,
paying particular attention to its superluminal and diffraction-free
properties. We spatially characterized the beam in the radial and on-axis
dimensions, and verified that the central peak does not spread over a
propagation distance of 73 cm. In addition, we measured the superluminal phase
and group velocities of the beam in free space. Both spatial and temporal
measurements show good agreement with the theoretical predictions.Comment: 5 pages, 6 figure
Surrogates, substudies, and real clinical end points in trials of drug-eluting stents**Editorials published in the Journal of the American College of Cardiologyreflect the views of the authors and do not necessarily represent the views of JACCor the American College of Cardiology.
Coupling of Liquid and Surface Chemistry in Urea SCR Systems
Close-coupled selective catalytic reduction (SCR) systems are one method to deal with tightening emission legislation for NO in internal combustion engines. Due to smaller mixing sections and at unfavourable boundary conditions, however, urea-water solution (UWS) droplets can impact on the SCR catalyst itself. To investigate this phenomenon further, this work develops a modeling capability of this process. Established mechanism for NH-SCR and HNCO hydrolysis from literature is integrated into DETCHEM and a 2D COMSOL model to simulate the influence in the SCR Channel. Simulations are validated against end-of-pipe experiments from literature and spatially resolved concentration profiles from a hot gas test rig with very good agreement. Finally, a channel simulation is coupled with a model to describe the catalytic decomposition of an urea droplet. The coupled simulation is able to simulate the influence of UWS droplet impact onto a catalyst channel. Fast droplet decomposition causes a peak in NH and HNCO in the single channel and thus increases NO conversion. However, the overall uniformity and efficiency are decreased, which is why droplet impact on the catalyst should be strictly avoided
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