Imperfect identity

Questions of identity over time are often hard to answer. A long tradition has it that such questions are somehow soft: they have no unique, determinate answer, and disagreements about them are merely verbal. I argue that this claim is not the truism it is taken to be. Depending on how it is understood, it turns out either to be false or to presuppose a highly contentious metaphysical claim

Radiation hardness of Ga0.5In0.5 P/GaAs tandem solar cells

The radiation hardness of a two-junction monolithic Ga sub 0.5 In sub 0.5 P/GaAs cell with tunnel junction interconnect was investigated. Related single junction cells were also studied to identify the origins of the radiation losses. The optimal design of the cell is discussed. The air mass efficiency of an optimized tandem cell after irradiation with 10(exp 15) cm (-2) 1 MeV electrons is estimated to be 20 percent using currently available technology

Structural Analysis of Test Flight Vehicles with Multifunctional Energy Storage

Under the NASA Aeronautics Research Mission Directorate (ARMD) Convergent Aeronautical Solutions (CAS) project, NASA Glenn Research Center has been leading Multifunctional Structures for High Energy Lightweight Load-bearing Storage (M-SHELLS) research efforts. The technology of integrating load-carrying structures with electrical energy storage capacity has the potential to reduce the overall weight of future electric aircraft. The proposed project goals were to develop M-SHELLS in the form of honeycomb coupons and subcomponents, integrate them into the structure, and conduct low-risk flight tests onboard a remotely piloted small aircraft. Experimental M-SHELLS energy-storing coupons were fabricated and tested in the laboratory for their electrical and mechanical properties. In this paper, finite element model development and structural analyses of two small test aircraft candidates are presented. The finite element analysis of the initial two-spar wing is described for strain, deflection, and weight estimation. After a test aircraft Tempest was acquired, a load- deflection test of the wing was conducted. A finite element model of the Tempest was then developed based on the test aircraft dimensions and construction detail. The component weight analysis from the finite element model and test measurements were correlated. Structural analysis results with multifunctional energy storage panels in the fuselage of the test vehicle are presented. Although the flight test was cancelled because of programmatic reasons and time constraints, the structural analysis results indicate that the mid-fuselage floor composite panel could provide structural integrity with minimal weight penalty while supplying electrical energy. To explore potential future applications of the multifunctional structure, analyses of the NASA X-57 Maxwell electric aircraft and a NASA N+3 Technology Conventional Configuration (N3CC) fuselage are presented. Secondary aluminum structure in the fuselage sub-floor and cargo area were partially replaced with reinforced five-layer composite panels with M-SHELLS honeycomb core. The N3CC fuselage weight reduction associated with each design without risking structural integrity are described. The structural analysis and weight estimation with the application of composite M-SHELLS panels to the N3CC fuselage indicate a 3.2% reduction in the fuselage structural weight, prior to accounting for the additional weight of core material required to complete the energy storage functionality

Information Asymmetry and the Cost of Going Public for Equity Carve Outs

We examine the relationship between asymmetric information and the cost of going public for equity carve-outs (ECOs) as compared to ordinary initial public offerings (IPOs). We decompose underpricing into the opportunity cost of issuance (OCI) and a measure of share retention. Compared to an average IPO, we find that ECOs have lower OCI and price revisions, but higher share retention and long-term returns. Compared to a matched sample of IPOs, however, we observe similar OCI and long-term returns, but still find ECOs have higher share retention. Our analysis suggests that documented pricing differences between ECOs and IPOs likely are attributable to the characteristics of ECO firms and not necessarily to status as a carve-out

Pretransplant varicella vaccination is cost-effective in pediatric renal transplantation

Because of the severe complications that may result from varicella zoster virus (VZV) infection following renal transplantation (Tx), transplanted varicella-susceptible children exposed to varicella are typically given varicella zoster immunoglobulin (VZIG) as prophylaxis or are admitted and treated with parenteral acyclovir if VZIG prophylaxis fails. As both VZIG and hospitalization are costly, prevention of varicella infection by vaccination could potentially result in significant cost savings in addition to decreasing morbidity and mortality. To test this hypothesis, we developed a decision-analysis model to evaluate the cost-effectiveness of vaccinating patients with chronic renal failure (CRF) against varicella prior to renal transplant. Under baseline assumptions, vaccination for varicella pretransplant was a cost-effective strategy, with a cost of $211 per patient vaccinated compared with$1,828 per patient not vaccinated. The magnitude of cost savings from vaccination was sensitive to variations in the cost of varicella vaccine, the percentage of patients hospitalized for treatment with acyclovir, and the percentage of patients exposed to varicella infection. One- and two-way sensitivity analyses confirmed that vaccination was the dominant cost-effective strategy under all conditions examined. We conclude that vaccination for varicella pretransplant is cost-effective for patients with CRF, and that the magnitude of cost savings is sensitive to the cost of hospitalization, the percentage of patients exposed to varicella, and the cost of varicella vaccination. Pending results of ongoing studies of the safety and efficacy of VZV vaccine in children with CRF, we recommend that VZV vaccine be given to all children with CRF.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73184/1/j.1399-3046.2001.00032.x.pd

Recoiling from a kick in the head-on collision of spinning black holes

Recoil ``kicks'' induced by gravitational radiation are expected in the inspiral and merger of black holes. Recently the numerical relativity community has begun to measure the significant kicks found when both unequal masses and spins are considered. Because understanding the cause and magnitude of each component of this kick may be complicated in inspiral simulations, we consider these effects in the context of a simple test problem. We study recoils from collisions of binaries with initially head-on trajectories, starting with the simplest case of equal masses with no spin and then adding spin and varying the mass ratio, both separately and jointly. We find spin-induced recoils to be significant relative to unequal-mass recoils even in head-on configurations. Additionally, it appears that the scaling of transverse kicks with spins is consistent with post-Newtonian theory, even though the kick is generated in the nonlinear merger interaction, where post-Newtonian theory should not apply. This suggests that a simple heuristic description might be effective in the estimation of spin-kicks.Comment: 12 pages, 10 figures. Replaced with published version, including more discussion of convergence and properties of final hol

Comparing the health and social protection effects of measles vaccination strategies in Ethiopia: An extended cost-effectiveness analysis

AbstractVaccination coverage rates often mask wide variation in access, uptake, and cost of providing vaccination. Financial incentives have been effective at creating demand for social services in a variety of settings. Using methods of extended cost-effectiveness analysis, we compare the health and economic implications of three different vaccine delivery strategies for measles vaccination in Ethiopia: i) routine immunization, ii) routine immunization with financial incentives, and iii) mass campaigns, known as supplemental immunization activities (SIAs). We examine annual birth cohorts of almost 3,000,000 births over a ten year period, exploring variation in these outcomes based on economic status to understand how various options may improve equity. SIAs naturally achieve higher levels of vaccine coverage, but at higher costs. Routine immunization combined with financial incentives bolsters demand among more economically vulnerable households. The relative appeal of routine immunization with financial incentives and SIAs will depend on the policy environment, including short-term financial limitations, time horizons, and the types of outcomes that are desired. While the impact of financial incentives has been more thoroughly studied in other policy arenas, such as education, consideration of this approach alongside standard vaccination models such as SIAs is timely given the dialog around measles eradication

Sub-barrier fusion of the oxygen isotopes: A more complete picture

We have measured the sub-barrier fusion cross sections for 16,17,18O on 16O and we present the data and the experimental method in detail. The data were analyzed with a one-dimensional potential barrier inversion model, a two-dimensional incoming wave boundary condition model, and a two-dimensional Wentzel-Kramers-Brillouin model. We find that a multidimensional model is necessary to describe the enhanced fusion cross sections in oxygen and the two-dimensional incoming wave boundary condition model suggests that a complete description of the fusion, inelastic, and elastic cross sections is possible