323 research outputs found
Mind the Gap - Issues in Overcoming the Information, Income, Wealth, and Supply Gaps Facing Potential Buyers of Affordable Homes
While the overall homeownership rate in the United States is at an all-time high, the gap between the ownership rates of low-income and higher-income households remains wide. In addition, homeownership rates in urban, low-income and minority communities lag behind. Lower-income families are constrained a lack of information about how to buy a home, by their inability to provide sufficient, stable income streams for debt service, by their lack of initial equity, and by their inability to find an home of adequate quality in a desirable location. This paper explores each of these constraints, or gaps, and potential solutions for each. We find addressing each of these gaps involves trade-offs, yet targeting the appropriate strategy for particular markets and populations may be able to help families become home owners. Information gaps are best addressed by programs that provide home buyer counseling and education. Federal funding and incentives for such programs have been declining throughout the last decade, however. Unless new homebuyers are well-prepared and supported, none of the sophisticated development and financial strategies will be successful. Income and wealth gaps are closely linked; bridging a wealth gap for a buyer, for example, may increase the buyer's income gap. While there are several strategies that seek to bridge these twin barriers, the most promising among them is the second mortgage. The supply gap is most pressing in faster-growing coastal cities, but is becoming a more significant constraint to homeownership nationally. Unfortunately, reliance on filtering and other traditional mechanisms for creating affordable homeownership opportunities has not proven effective in recent years. Serious consideration should be paid to new production programs and policies that can enhance the supply of affordable owner-occupied units in targeted areas. Overall, a menu of strategies exists, each being appropriate for targeted households in a given housing market context. More attention needs to be focused on this menu, rather than a one-size fits all strategy
The Role of Consistency and Diversity in Building Knowledge in Family Preservation
Family preservation has been criticized for implementing programs that are not theoretically founded. One result of this circumstance is a lack of information regarding processes and outcomes of family preservation services. The knowledge base of family preservation is thus rather limited at present and will remain limited unless theory is consistently integrated within individual programs. A model for conceptualizing how theoretical consistency may be implemented within programs is presented and applied to family preservation. It is also necessary for programs to establish theoretical consistency before theoretical diversity, both within individual and across multiple programs, in order to advance the field in meaningful ways. A developmental cycle of knowledge generation is presented and applied to family preservation
Molecular Beams
Contains reports on three research projects.Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DA 28-043-AMC-02536(E
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A high-average-power FEL for industrial applications
CEBAF has developed a comprehensive conceptual design of an industrial user facility based on a kilowatt UV (150-1000 nm) and IR (2-25 micron) FEL driven by a recirculating, energy-recovering 200 MeV superconducting radio-frequency (SRF) accelerator. FEL users{endash}CEBAF`s partners in the Laser Processing Consortium, including AT&T, DuPont, IBM, Northrop-Grumman, 3M, and Xerox{endash}plan to develop applications such as polymer surface processing, metals and ceramics micromachining, and metal surface processing, with the overall effort leading to later scale-up to industrial systems at 50-100 kW. Representative applications are described. The proposed high-average-power FEL overcomes limitations of conventional laser sources in available power, cost-effectiveness, tunability and pulse structure. 4 refs., 3 figs., 2 tabs
Electric charge quantization without anomalies?
In gauge theories like the standard model, the electric charges of the
fermions can be heavily constrained from the classical structure of the theory
and from the cancellation of anomalies. We argue that the anomaly conditions
are not quite as well motivated as the classical constraints, since it is
possible that new fermions could exist which cancel potential anomalies. For
this reason we examine the classically allowed electric charges of the known
fermions and we point out that the electric charge of the tau neutrino is
classically allowed to be non-zero. The experimental bound on the electric
charge of the tau neutrino is many orders of magnitude weaker than for any
other known neutrino. We discuss possible modifications of the minimal standard
model such that electric charge is quantized classically.Comment: 10 McGill/93-3
Vacuum Polarization and the Electric Charge of the Positron
We show that higher-order vacuum polarization would contribute a measureable
net charge to atoms, if the charges of electrons and positrons do not balance
precisely. We obtain the limit for the sum of
the charges of electron and positron. This also constitutes a new bound on
certain violations of PCT invariance.Comment: 9 pages, 1 figure attached as PostScript file, DUKE-TH-92-38. Revised
versio
Comparison of the tetrahedron method to smearing methods for the electronic density of states
The electronic density of states (DOS) highlights fundamental properties of materials that oftentimes dictate their properties, such as the band gap and Van Hove singularities. In this short note, we discuss how sharp features of the density of states can be obscured by smearing methods (such as the Gaussian and Fermi smearing methods) when calculating the DOS. While the common approach to reach a "converged" density of states of a material is to increase the discrete k-point mesh density, we show that the DOS calculated by smearing methods can appear to converge but not to the correct DOS. Employing the tetrahedron method for Brillouin zone integration resolves key features of the density of states far better than smearing methods
Tractable Fragments of Temporal Sequences of Topological Information
In this paper, we focus on qualitative temporal sequences of topological
information. We firstly consider the context of topological temporal sequences
of length greater than 3 describing the evolution of regions at consecutive
time points. We show that there is no Cartesian subclass containing all the
basic relations and the universal relation for which the algebraic closure
decides satisfiability. However, we identify some tractable subclasses, by
giving up the relations containing the non-tangential proper part relation and
not containing the tangential proper part relation. We then formalize an
alternative semantics for temporal sequences. We place ourselves in the context
of the topological temporal sequences describing the evolution of regions on a
partition of time (i.e. an alternation of instants and intervals). In this
context, we identify large tractable fragments
Dental and physical therapy faculty collaborate in assessing and educating dental students on musculoskeletal disorders
Introduction: Research shows 54% to 93% of practicing dentists suffer from musculoskeletal disorders (MSDs), with many developing afflictions early in their careers. Studies also show that dental students are developing MSDs early in their professional education. Objective: The research goal was to quantify the prevalence, anatomical location and initial onset of MSDs among first-year dental students. The study also assessed the students’ self-reported opinion as to whether there were enough educational touchpoints to improve their ergonomics in daily activities. Methods: At the conclusion of a 9-month preclinical restorative course, that included 2 lectures on MSDs, ergonomics, and postural cueing sessions, a dental and physical therapy faculty member administered a survey to 143 first-year dental students. This survey included questions about the history and presentation of the students’ MSD symptoms and their opinion on the relative value of the educational interventions. Results: There was a 96.5% response rate to the survey with 87.8% of students reporting mild to moderate pain. The cervical spine (41.7%) and hands (42.4%) were the most common areas afflicted. 55.4% reported pain commencing 1 month after starting in the simulation clinic. Over 60.9% of students “agreed” or “somewhat agreed” that the 2 sessions of hands-on ergonomic educational interventions resulted in improved biomechanics and students requested additional educational resources. Conclusion: Dental students are developing MSDs as soon as 1 month after commencing dental school. Dental education should include ongoing ergonomic training throughout the curriculum to help students prevent MSDs
Constraints on the Electrical Charge Asymmetry of the Universe
We use the isotropy of the Cosmic Microwave Background to place stringent
constraints on a possible electrical charge asymmetry of the universe. We find
the excess charge per baryon to be in the case of a uniform
distribution of charge, where is the charge of the electron. If the charge
asymmetry is inhomogeneous, the constraints will depend on the spectral index,
, of the induced magnetic field and range from
() to (). If one could further
assume that the charge asymmetries of individual particle species are not
anti-correlated so as to cancel, this would imply, for photons, ; for neutrinos, ; and for heavy (light) dark
matter particles ().Comment: New version to appear in JCA
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