Birkhoff for Lovelock Redux

We show succinctly that all metric theories with second order field equations obey Birkhoff's theorem: their spherically symmetric solutions are static.Comment: Submitted to CQ

Lunar Resource Assessment: an Industry Perspective

The goals of the U.S. space program are to return to the Moon, establish a base, and continue onward to Mars. To accomplish this in a relatively short time frame and to avoid the high costs of transporting materials from the Earth, resources on the Moon will need to be mined. Oxygen will be one of the most important resources, to be used as a rocket propellant and for life support. Ilmenite and lunar regolith have both been considered as ores for the production of oxygen. Resource production on the Moon will be a very important part of the U.S. space program. To produce resources we must explore to identify the location of ore or feedback and calculate the surface and underground reserves. Preliminary resource production tests will provide the information that can be used in final plant design. Bechtel Corporation's experience in terrestrial engineering and construction has led to an interest in lunar resource assessment leading to the construction of production facilities on the Moon. There is an intimate link between adequate resource assessment to define feedstock quantity and quality, material processing requirements, and the successful production of lunar oxygen. Although lunar resource assessment is often viewed as a research process, the engineering and production aspects are very important to consider. Resource production often requires the acquisition of different types, scales, or resolutions of data than that needed for research, and it is needed early in the exploration process. An adequate assessment of the grade, areal extent, and depth distribution of the resources is a prerequisite to mining. The need for a satisfactory resource exploration program using remote sensing techniques, field sampling, and chemical and physical analysis is emphasized. These data can be used to define the ore for oxygen production and the mining, processing facilities, and equipment required

A National Dialogue on Health Information Technology and Privacy

Increasingly, government leaders recognize that solving the complex problems facing America today will require more than simply keeping citizens informed. Meeting challenges like rising health care costs, climate change and energy independence requires increased level of collaboration. Traditionally, government agencies have operated in silos -- separated not only from citizens, but from each other, as well. Nevertheless, some have begun to reach across and outside of government to access the collective brainpower of organizations, stakeholders and individuals.The National Dialogue on Health Information Technology and Privacy was one such initiative. It was conceived by leaders in government who sought to demonstrate that it is not only possible, but beneficial and economical, to engage openly and broadly on an issue that is both national in scope and deeply relevant to the everyday lives of citizens. The results of this first-of-its-kind online event are captured in this report, together with important lessons learned along the way.This report served as a call to action. On his first full day in office, President Obama put government on notice that this new, more collaborative model can no longer be confined to the efforts of early adopters. He called upon every executive department and agency to "harness new technology" and make government "transparent, participatory, and collaborative." Government is quickly transitioning to a new generation of managers and leaders, for whom online collaboration is not a new frontier but a fact of everyday life. We owe it to them -- and the citizens we serve -- to recognize and embrace the myriad tools available to fulfill the promise of good government in the 21st Century.Key FindingsThe Panel recommended that the Administration give stakeholders the opportunity to further participate in the discussion of heath IT and privacy through broader outreach and by helping the public to understand the value of a person-centered view of healthcare information technology

Social and Nonsocial Decentration in Hearing-Impaired and Normal Hearing Children

Tweny-three hearing-impaired and 25 normally hearing children between 7 and 14 years of age were administered a social decentration task, a nonsocial decentration task (a set of conservation problems), and a test of nonverbal intelligence. Although the two groups did not differ with respect to nonverbal intelligence, the hearing-impaired children obtained significantlv lower scores than their normally hearing peers on both the social and nonsocial decentration measures. Within both groups, there was a significant positive correlation between social decentration and nonsocial decentration, which is consistent with Piaget\u27s contention that centration-decentration is a cognitive dimension underlying the structuring of both social and nonsocial content. Within the hearing-impaired sample, degree of hearing loss was not associated with either social or nonsocial decentration

Extraordinary sensitivity of the electronic structure and properties of single-walled carbon nanotubes to molecular charge-transfer

Interaction of single-walled carbon nanotubes with electron donor and acceptor molecules causes significant changes in the electronic and Raman spectra, the relative proportion of the metallic species increasing on electron donation through molecular charge transfer, as also verified by electrical resistivity measurements.Comment: 15 pages, 5 figurre

Heterogeneity in susceptibility dictates the order of epidemiological models

The fundamental models of epidemiology describe the progression of an infectious disease through a population using compartmentalized differential equations, but do not incorporate population-level heterogeneity in infection susceptibility. We show that variation strongly influences the rate of infection, while the infection process simultaneously sculpts the susceptibility distribution. These joint dynamics influence the force of infection and are, in turn, influenced by the shape of the initial variability. Intriguingly, we find that certain susceptibility distributions (the exponential and the gamma) are unchanged through the course of the outbreak, and lead naturally to power-law behavior in the force of infection; other distributions often tend towards these "eigen-distributions" through the process of contagion. The power-law behavior fundamentally alters predictions of the long-term infection rate, and suggests that first-order epidemic models that are parameterized in the exponential-like phase may systematically and significantly over-estimate the final severity of the outbreak

From atomic attrition to mild wear at multi-asperity interfaces:The wear of <i>hard</i> Si₃N₄ repeatedly contacted against <i>soft</i> Si

Wear causes surfaces to be irreversibly damaged, thereby incurring significant economic cost, for instance in the semiconductor industry. Much progress has been made in describing wear at single asperity interfaces between silicon based materials (Si, SiOx, Si3N4), translating the fundamental understanding of wear into wear predictions and control over wear. Yet, predicting and controlling wear at industrially relevant multi-asperity interfaces remains a challenge, especially when considering the wear of the harder material subjected to repeated, nanometric scale displacement. We studied pre-sliding Si3N4-on-Si wear using the atomic force microscopy topography difference method and showed that the harder Si3N4 wears through either atomic attrition or ductile removal enhanced by subsurface damage, depending on the magnitude of the local Si3N4-on-Si contact pressure. Our methods and results bridge fundamental insight into wear based on nanoscale studies to industrial applications.</p

Addressing student models of energy loss in quantum tunnelling

We report on a multi-year, multi-institution study to investigate student reasoning about energy in the context of quantum tunnelling. We use ungraded surveys, graded examination questions, individual clinical interviews, and multiple-choice exams to build a picture of the types of responses that students typically give. We find that two descriptions of tunnelling through a square barrier are particularly common. Students often state that tunnelling particles lose energy while tunnelling. When sketching wave functions, students also show a shift in the axis of oscillation, as if the height of the axis of oscillation indicated the energy of the particle. We find inconsistencies between students' conceptual, mathematical, and graphical models of quantum tunnelling. As part of a curriculum in quantum physics, we have developed instructional materials to help students develop a more robust and less inconsistent picture of tunnelling, and present data suggesting that we have succeeded in doing so.Comment: Originally submitted to the European Journal of Physics on 2005 Feb 10. Pages: 14. References: 11. Figures: 9. Tables: 1. Resubmitted May 18 with revisions that include an appendix with the curriculum materials discussed in the paper (4 page small group UW-style tutorial