Fixing Social Security: is the surplus the solution?

It may seem an attractive proposal-the Administration's plan of using projected budget surpluses to restore Social Security's finances-but it obscures the real trade-off we face in tackling this problem. The proposal is essentially a change in the accounting treatment of surpluses, deficits, and debt held by the public and in the Social Security Trust Fund. It would in no way alter the fundamental imbalance that afflicts the nation's most basic pension program.Social security

The role of freestream turbulence scale in subsonic flow separation

The clarification of the role of freestream turbulence scale in determining the location of boundary layer separation is discussed. Modifications to the test facility were completed. Wind tunnel flow characteristics, including turbulence parameters, were determined with two turbulence generating grids, as well as no grid. These results are summarized. Initial results on the role of scale on turbulent boundary layer separation on the upper surface of an airfoil model are also discussed

Magnetotransport properties of individual InAs nanowires

We probe the magnetotransport properties of individual InAs nanowires in a field effect transistor geometry. In the low magnetic field regime we observe magnetoresistance that is well described by the weak localization (WL) description in diffusive conductors. The weak localization correction is modified to weak anti-localization (WAL) as the gate voltage is increased. We show that the gate voltage can be used to tune the phase coherence length ($l_\phi$) and spin-orbit length ($l_{so}$) by a factor of $\sim$ 2. In the high field and low temperature regime we observe the mobility of devices can be modified significantly as a function of magnetic field. We argue that the role of skipping orbits and the nature of surface scattering is essential in understanding high field magnetotransport in nanowires

Constructing Synchronously Rotating Double White Dwarf Binaries

We have developed a self-consistent-field technique similar to the one described by Hachisu, Eriguchi, & Nomoto (1986b) that can be used to construct detailed force-balanced models of synchronously rotating, double white dwarf (DWD) binaries that have a wide range of total masses, mass ratios, and separations. In addition to providing a computational tool that can be used to provide quiet initial starts for dynamical studies of the onset of mass transfer in DWD systems, we show that this SCF technique can be used to construct model sequences that mimic the last portion of the detached inspiral phase of DWD binary evolutions, and semi-detached model sequences that mimic a phase of conservative mass transfer.Comment: 51 pages, 10 figures, submitted for publication in Astrophysical Journal Supplement Serie

Long Term Outcomes of Pediatric Idiopathic Intermediate Uveitis

Purpose: To describe the course of childhood-onset intermediate uveitis without associated systemic disease, and investigate determinants of outcomes. / Design: A retrospective clinical cohort study. / Setting: Institutional. / Patients: 125 children (221 eyes) (aged 16 years and under). / Main Outcomes and Measures: Outcomes of interest were visual acuity, severity of inflammation, and the occurrence of sight-threatening complications. Variables examined included age and clinical findings at presentation, treatment, and duration of follow-up. Multivariable analysis was undertaken to investigate potential predictors of outcomes. / Results: Median follow-up duration was 57 months. At presentation, best-corrected visual acuity worse than 20/160 was recorded in 11 (4.4%) eyes, and significant vitreous haze (≥2+SUN) in 35 (14%) eyes. Corticosteroid-sparing agents were used in 41 children (33%), with methotrexate most commonly used (27 children, 21.6%). The most frequent complications were raised intraocular pressure n=65 (29.4%), cataract n=41 (18.5%), and cystoid macular edema n=29 (13.1%). At the last visit, 116 (92.8%) patients achieved best-corrected vision of 20/40 or better with quiescent uveitis. The absence of the use of a steroid-sparing immunomodulatory agent was the strongest predictive factor for the development of new macular edema (OR 6.3, 95% CI 2.3 – 16.9, p<0.001) or glaucoma (OR, 6.6, 95% CI 2.5 – 17.9, p<0.001) over the period of observation. / Conclusions: The visual outcomes of childhood-onset idiopathic intermediate uveitis are favorable. The frequency of sight-threatening sequelae of inflammation, which confer a life-long risk of further visual loss, is high. The use of immunomodulatory therapy is associated with a lower risk of developing macular edema and ocular hypertension

Microwave Spectroscopy

Contains reports on five research projects

Microwave Spectroscopy

Contains reports on three research projects

QED radiative corrections to the decay pi^0 to e^+e^-

We reconsider QED radiative corrections (RC) to the $\pi^{0}\to e^{+}e^{-}$ decay width. One kind of RC investigated earlier has a renormalization group origin and can be associated with the final state interaction of electron and positron. It determines the distribution of lepton pair invariant masses in the whole kinematic region. The other type of RC has a double-logarithmic character and is related to almost on-mass-shell behavior of the lepton form factors. The total effect of RC for the $\pi^{0}\to e^{+}e^{-}$ decay is estimated to be 3.2% and for the decay $\eta \to e^{+}e^{-}$ is 4.3%.Comment: 12 pages, 3 figure

Fabrication of Sawfish photonic crystal cavities in bulk diamond

Color centers in diamond are quantum systems with optically active spin-states that show long coherence times and are therefore a promising candidate for the development of efficient spin-photon interfaces. However, only a small portion of the emitted photons is generated by the coherent optical transition of the zero-phonon line (ZPL), which limits the overall performance of the system. Embedding these emitters in photonic crystal cavities improves the coupling to the ZPL photons and increases their emission rate. Here, we demonstrate the fabrication process of "Sawfish" cavities, a design recently proposed that has the experimentally-realistic potential to simultaneously enhance the emission rate by a factor of 46 and couple photons into a single-mode fiber with an efficiency of 88%. The presented process allows for the fabrication of fully suspended devices with a total length of 20.5 $\mu$m and features size as small as 40 nm. The optical characterization shows fundamental mode resonances that follow the behavior expected from the corresponding design parameters and quality (Q) factors as high as 3825. Finally, we investigate the effects of nanofabrication on the devices and show that, despite a noticeable erosion of the fine features, the measured cavity resonances deviate by only 0.9 (1.2)% from the corresponding simulated values. This proves that the Sawfish design is robust against fabrication imperfections, which makes it an attractive choice for the development of quantum photonic networks.Comment: 7 pages, 9 figure

On the interpretation of spin-polarized electron energy loss spectra

We study the origin of the structure in the spin-polarized electron energy loss spectroscopy (SPEELS) spectra of ferromagnetic crystals. Our study is based on a 3d tight-binding Fe model, with constant onsite Coulomb repulsion U between electrons of opposite spin. We find it is not the total density of Stoner states as a function of energy loss which determines the response of the system in the Stoner region, as usually thought, but the densities of Stoner states for only a few interband transitions. Which transitions are important depends ultimately on how strongly umklapp processes couple the corresponding bands. This allows us to show, in particular, that the Stoner peak in SPEELS spectra does not necessarily indicate the value of the exchange splitting energy. Thus, the common assumption that this peak allows us to estimate the magnetic moment through its correlation with exchange splitting should be reconsidered, both in bulk and surface studies. Furthermore, we are able to show that the above mechanism is one of the main causes for the typical broadness of experimental spectra. Finally, our model predicts that optical spin waves should be excited in SPEELS experiments.Comment: 11 pages, 7 eps figures, REVTeX fil