NiO Exchange Bias Layers Grown by Direct Ion Beam Sputtering of a Nickel Oxide Target

A new process for fabricating NiO exchange bias layers has been developed. The process involves the direct ion beam sputtering (IBS) of a NiO target. The process is simpler than other deposition techniques for producing NiO buffer layers, and facilitates the deposition of an entire spin-valve layered structure using IBS without breaking vacuum. The layer thickness and temperature dependence of the exchange field for NiO/NiFe films produced using IBS are presented and are similar to those reported for similar films deposited using reactive magnetron sputtering. The magnetic properties of highly textured exchange couples deposited on single crystal substrates are compared to those of simultaneously deposited polycrystalline films, and both show comparable exchange fields. These results are compared to current theories describing the exchange coupling at the NiO/NiFe interface.Comment: 9 pages, Latex 2.09, 3 postscript figures. You can also this manuscript at http://www.wsrcc.com/alison/fixed-nio/manuscript.html To be published in _IEEE Trans. Magn._, Nov. 199

Bayesian photon counting with electron-multiplying charge coupled devices (EMCCDs)

The EMCCD is a CCD type that delivers fast readout and negligible detector noise, making it an ideal detector for high frame rate applications. Because of the very low detector noise, this detector can potentially count single photons. Considering that an EMCCD has a limited dynamical range and negligible detector noise, one would typically apply an EMCCD in such a way that multiple images of the same object are available, for instance, in so called lucky imaging. The problem of counting photons can then conveniently be viewed as statistical inference of flux or photon rates, based on a stack of images. A simple probabilistic model for the output of an EMCCD is developed. Based on this model and the prior knowledge that photons are Poisson distributed, we derive two methods for estimating the most probable flux per pixel, one based on thresholding, and another based on full Bayesian inference. We find that it is indeed possible to derive such expressions, and tests of these methods show that estimating fluxes with only shot noise is possible, up to fluxes of about one photon per pixel per readout.Comment: Fixed a few typos compared to the published versio

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Impact of health insurance expansions on nonelderly adults with hypertension.

Introduction Hypertension is a risk factor for cardiovascular disease (CVD), the leading cause of death in the United States. The treatment and control of hypertension is inadequate, especially among patients without health insurance coverage. The Affordable Care Act offered an opportunity to improve hypertension management by increasing the number of people covered by insurance. This study predicts the long-term effects of improved hypertension treatment rates due to insurance expansions on the prevalence and mortality rates of CVD of nonelderly Americans with hypertension. Methods We developed a state-transition model to simulate the lifetime health events of the population aged 25 to 64 years. We modeled the effects of insurance coverage expansions on the basis of published findings on the relationship between insurance coverage, use of antihypertensive medications, and CVD-related events and deaths. Results The model projected that currently anticipated health insurance expansions would lead to a 5.1% increase in treatment rate among hypertensive patients. Such an increase in treatment rate is estimated to lead to 111,000 fewer new coronary heart disease events, 63,000 fewer stroke events, and 95,000 fewer CVD-related deaths by 2050. The estimated benefits were slightly greater for men than for women and were greater among nonwhite populations. Conclusion Federal and state efforts to expand insurance coverage among nonelderly adults could yield significant health benefits in terms of CVD prevalence and mortality rates and narrow the racial/ethnic disparities in health outcomes for patients with hypertension

A comparative evaluation of different models and brands of direct ophthalmoscopes and retinoscopes

The purpose of this study was to compare the various ophthalmoscopes and streak retinoscopes currently available on the U.S. market. Subjective and objective tests were utilized to assess overall performance. Each instrument tested received a sub score based on performance in each of several subjective categories which were then combined to arrive at a total score. The instruments were then ranked from highest overall score to the lowest. The Keeler Vista 20 was the highest rated ophthalmoscope largely due to excellent optical clarity. The Vista was followed by the Keeler Specialist, Propper MMI, Neitz BX alpha, Welch Allyn 11730, Visuscope, Ri-Scope and Heine Autofoc 2. Of the pocket ophthalmoscopes tested the Keeler rated first again, followed by Neitz, Welch Allyn, Propper and Maylite. Streak retinoscopes evaluation placed the Neitz on top with the Welch Allyn prototype, Propper and Keeler units placing second, third and fourth

Ion counting efficiencies at the IGISOL facility

At the IGISOL-JYFLTRAP facility, fission mass yields can be studied at high precision. Fission fragments from a U target are passing through a Ni foil and entering a gas filled chamber. The collected fragments are guided through a mass separator to a Penning trap where their masses are identified. This simulation work focuses on how different fission fragment properties (mass, charge and energy) affect the stopping efficiency in the gas cell. In addition, different experimental parameters are varied (e. g. U and Ni thickness and He gas pressure) to study their impact on the stopping efficiency. The simulations were performed using the Geant4 package and the SRIM code. The main results suggest a small variation in the stopping efficiency as a function of mass, charge and kinetic energy. It is predicted that heavy fragments are stopped about 9% less efficiently than the light fragments. However it was found that the properties of the U, Ni and the He gas influences this behavior. Hence it could be possible to optimize the efficiency.Comment: 52 pages, 44 figure

Surface effects on the Mott-Hubbard transition in archetypal V2_2O3_3

We present an experimental and theoretical study exploring surface effects on the evolution of the metal-insulator transition in the model Mott-Hubbard compound Cr-doped V$_2$O$_3$. We find a microscopic domain formation that is clearly affected by the surface crystallographic orientation. Using scanning photoelectron microscopy and X-ray diffraction, we find that surface defects act as nucleation centers for the formation of domains at the temperature-induced isostructural transition and favor the formation of microscopic metallic regions. A density functional theory plus dynamical mean field theory study of different surface terminations shows that the surface reconstruction with excess vanadyl cations leads to doped, and hence more metallic surface states, explaining our experimental observations.Comment: 5 pages, 4 figure

Domain size effects on the dynamics of a charge density wave in 1T-TaS2

Recent experiments have shown that the high temperature incommensurate (I) charge density wave (CDW) phase of 1T-TaS2 can be photoinduced from the lower temperature, nearly commensurate (NC) CDW state. Here we report a time-resolved x-ray diffraction study of the growth process of the photoinduced I-CDW domains. The layered nature of the material results in a marked anisotropy in the size of the photoinduced domains of the I-phase. These are found to grow self-similarly, their shape remaining unchanged throughout the growth process. The photoinduced dynamics of the newly formed I-CDW phase was probed at various stages of the growth process using a double pump scheme, where a first pump creates I-CDW domains and a second pump excites the newly formed I-CDW state. We observe larger magnitudes of the coherently excited I-CDW amplitude mode in smaller domains, which suggests that the incommensurate lattice distortion is less stable for smaller domain sizes.Comment: 8 pages, 8 figure