A comparison of two methods of estimating propensity scores after multiple imputation

In many observational studies, analysts estimate treatment effects using propensity scores, e.g. by matching or sub-classifying on the scores. When some values of the covariates are missing, analysts can use multiple imputation to fill in the missing data, estimate propensity scores based on the m completed datasets, and use the propensity scores to estimate treatment effects. We compare two approaches to implement this process. In the first, the analyst estimates the treatment effect using propensity score matching within each completed data set, and averages the m treatment effect estimates. In the second approach, the analyst averages the m propensity scores for each record across the completed datasets, and performs propensity score matching with these averaged scores to estimate the treatment effect. We compare properties of both methods via simulation studies using artificial and real data. The simulations suggest that the second method has greater potential to produce substantial bias reductions than the first, particularly when the missing values are predictive of treatment assignment

Can we identify patients with high risk of osteoarthritis progression who will respond to treatment? A focus on epidemiology and phenotype of osteoarthritis

Osteoarthritis is a syndrome affecting a variety of patient profiles. A European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis and the European Union Geriatric Medicine Society working meeting explored the possibility of identifying different patient profiles in osteoarthritis. The risk factors for the development of osteoarthritis include systemic factors (e.g., age, sex, obesity, genetics, race, and bone density) and local biomechanical factors (e.g., obesity, sport, joint injury, and muscle weakness); most also predict disease progression, particularly joint injury, malalignment, and synovitis/effusion. The characterization of patient profiles should help to better orientate research, facilitate trial design, and define which patients are the most likely to benefit from treatment. There are a number of profile candidates. Generalized, polyarticular osteoarthritis and local, monoarticular osteoarthritis appear to be two different profiles; the former is a feature of osteoarthritis co-morbid with inflammation or the metabolic syndrome, while the latter is more typical of post-trauma osteoarthritis, especially in cases with severe malalignment. Other biomechanical factors may also define profiles, such as joint malalignment, loss of meniscal function, and ligament injury. Early- and late-stage osteoarthritis appear as separate profiles, notably in terms of treatment response. Finally, there is evidence that there are two separate profiles related to lesions in the subchondral bone, which may determine benefit from bone-active treatments. Decisions on appropriate therapy should be made considering clinical presentation, underlying pathophysiology, and stage of disease. Identification of patient profiles may lead to more personalized healthcare, with more targeted treatment for osteoarthritis

Dealing Automatically with Exceptions by Introducing Specificity in ASP

Answer Set Programming (ASP), via normal logic programs, is known as a suitable framework for default reasoning since it offers both a valid formal model and operational systems. However, in front of a real world knowledge representation problem, it is not easy to represent information in this framework. That is why the present article proposed to deal with this issue by generating in an automatic way the suitable normal logic program from a compact representation of the information. This is done by using a method, based on specificity, that has been developed for default logic and which is adapted here to ASP both in theoretical and practical points of view

Magnetic polarons in weakly doped high-Tc superconductors

We consider a spin Hamiltonian describing $d$-$d$ exchange interactions between localized spins $d$ of a finite antiferromagnet as well as $p$-$d$ interactions between a conducting hole ($p$) and localized spins. The spin Hamiltonian is solved numerically with use of Lanczos method of diagonalization. We conclude that $p$-$d$ exchange interaction leads to localization of magnetic polarons. Quantum fluctuations of the antiferromagnet strengthen this effect and make the formation of polarons localized in one site possible even for weak $p$-$d$ coupling. Total energy calculations, including the kinetic energy, do not change essentially the phase diagram of magnetic polarons formation. For parameters reasonable for high-$T_c$ superconductors either a polaron localized on one lattice cell or a small ferron can form. For reasonable values of the dielectric function and $p$-$d$ coupling, the contributions of magnetic and phonon terms in the formation of a polaron in weakly doped high-$T_c$ materials are comparable.Comment: revised, revtex-4, 12 pages 8 eps figure

Energy levels in 25198Cf populated in the α decay of 255100Fm

Gamma-ray spectra of a 20-h 255Fm source containing ∼1 mCi activity were measured with a 25% Ge detector and a low-energy photon spectrometer (LEPS). Gamma lines with intensities as low as 1.0 × 10-6% per 255Fm α decay were observed. Gamma-gamma coincidence spectra of a 255Fm sample were measured with the GAMMASPHERE array. A comparison of the γ-ray spectrum gated by the Cf Kα x-ray peak with the γ-singles spectrum provided spins of the excited states in 251Cf. The γ-ray data, in conjunction with previously measured 250Cf(d,p) reaction data, allowed us to characterize several single-particle and vibrational states above the N=152 subshell gap

Experimental study of the Ni56(He3,d)Cu57 reaction in inverse kinematics

Measurements of (He3,d) reactions can provide information on the proton widths of states that play a role in astrophysically important (p,γ) reactions. We report on the first study of the (He3,d) reaction in inverse kinematics with a Ni56(T1/2=6.1 d) ion beam. The Q-value resolution of ~keV achieved in this experiment was sufficient to separate the transitions populating the ground state and the 1/2 - 5/2- doublet at Ex~1.1 MeV in Cu57. Prospects for similar (He3,d) experiments with improved energy resolution are also discussed

High-spin properties of octupole bands in 240Pu and 248Cm

The properties of superdeformed bands in 191,192Hg and 192,193Tl have been studied using the cranked Hartree-Fock-Bogoliubov method with the Lipkin-Nogami prescription, the Skm* interaction, and a surface-delta, density-dependent pairing force. In particular, quasiparticle excitations involving intruder orbitals are analyzed in detail. Comparisons between data and calculations are performed for J (2) moments, quadrupole moments, spins, transition energies, and alignments

Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set

We report a measurement of the bottom-strange meson mixing phase \beta_s using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays in which the quark-flavor content of the bottom-strange meson is identified at production. This measurement uses the full data set of proton-antiproton collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity. We report confidence regions in the two-dimensional space of \beta_s and the B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2, -1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in agreement with the standard model expectation. Assuming the standard model value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +- 0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +- 0.009 (syst) ps, which are consistent and competitive with determinations by other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012

Octupole correlations in the pu isotopes: From vibration to static deformation?

In a series of measurements with Gammasphere, striking differences were found between the yrast and negative parity bands in 238-240Pu and those in 241-244Pu. These differences can be linked to variations with mass of the strength of octupole correlations. At the highest spins, 238-240Pu are found to exhibit properties associated with stable octupole deformation, suggesting that a transition with spin from a vibration to stable deformation may have occurred

Direct decay from the superdeformed band to the yrast line in 66152Dy86

A number of single step linking transitions were observed in 152Dy. The first superdeformed (SD) band was linked to the normal yrats states and its spin, parity and excitation energy was established. An angular distribution analysis of the 4011 keV transition was performed to determine the spin of the 11893 keV SD level. The excitation energy of the lowest SD band member was 10644 keV and its spin and parity was determined to be 24+