X-ray absorption branching ratio in actinides: LDA+DMFT approach

To investigate the x-ray absorption (XAS) branching ratio from the core 4d to valence 5f states, we set up a theoretical framework by using a combination of density functional theory in the local density approximation and Dynamical Mean Field Theory (LDA+DMFT), and apply it to several actinides. The results of the LDA+DMFT reduces to the band limit for itinerant systems and to the atomic limit for localized f electrons, meaning a spectrum of 5f itinerancy can be investigated. Our results provides a consistent and unified view of the XAS branching ratio for all elemental actinides, and is in good overall agreement with experiments.Comment: 6 pages, 4 figure

Consistent use of a combination product versus a single product in a safety trial of the diaphragm and microbicide in Harare, Zimbabwe.

BACKGROUND: We examined the use and acceptability of a combination product (diaphragm and gel) compared to a single product (gel) during a 6-month safety trial in Zimbabwe. STUDY DESIGN: Women were randomized to the use of a diaphragm with gel or the use of gel alone, in addition to male condoms. Ever use and use of study product on the last act of sexual intercourse were assessed monthly by Audio Computer-Assisted Self-Interviewing. Acceptability, correct use and consistent use (use at every sexual act during the previous 3 months) were measured on the last visit by face-to-face interview. Predictors of consistent use were examined using multivariate logistic regression analyses. RESULTS: In this sample of 117 sexually active, monogamous, contracepting women, rates of consistent use were similar in both groups (59.7% for combination method vs. 56.4% for gel alone). Product acceptability was high, but was not independently associated with consistent use. Independent predictors of consistent use included age [adjusted odds ratio (AOR)=1.08; 95% confidence interval (95% CI)=1.01-1.16], consistent condom use (AOR=3.85; 95% CI=1.54-9.63) and having a partner who approves of product use (AOR=2.66; 95% CI=1.10-6.39). CONCLUSIONS: Despite high reported acceptability and few problems with the products, the participants reported only moderate product adherence levels. Consistent use of condoms and consistent use of products were strongly associated. If observed in other studies, this may bias the estimation of product effectiveness in future trials of female-controlled methods

Dynamical model of the dielectric screening of conjugated polymers

A dynamical model of the dielectric screening of conjugated polymers is introduced and solved using the density matrix renormalization group method. The model consists of a line of quantized dipoles interacting with a polymer chain. The polymer is modelled by the Pariser-Parr-Pople (P-P-P) model. It is found that: (1) Compared to isolated, unscreened single chains, the screened 1Bu- exciton binding energy is typically reduced by ca. 1 eV to just over 1 eV; (2) Covalent (magnon and bi-magnon) states are very weakly screened compared to ionic (exciton) states; (3) Screening of the 1Bu- exciton is closer to the dispersion than solvation limit.Comment: 12 pages, 2 figure

Four-loop logarithms in 3d gauge + Higgs theory

We discuss the logarithmic contributions to the vacuum energy density of the three-dimensional SU(3) + adjoint Higgs theory in its symmetric phase, and relate them to numerical Monte Carlo simulations. We also comment on the implications of these results for perturbative and non-perturbative determinations of the pressure of finite-temperature QCD.Comment: 3 pages, Lattice2002(nonzerot

Application of Time-to-Event Methods in the Assessment of Safety in Clinical Trials

Since randomized controlled trials (RCT) are typically designed and powered for efficacy rather than safety, power is an important concern in the analysis of the effect of treatment on the occurrence of adverse events (AE). These outcomes are often time-to-event outcomes which will naturally be subject to right-censoring due to early patient withdrawals. In the analysis of the treatment effect on such an outcome, gains in efficiency, and thus power, can be achieved by exploiting covariate information. We apply the targeted maximum likelihood methodology to the estimation of treatment specific survival at a fixed end point for right-censored survival outcomes. This approach provides a method for covariate adjustment, that under no or uninformative censoring, does not require any additional parametric modeling assumptions, and, under informative censoring, is consistent under consistent estimation of the censoring mechanism or the conditional hazard for survival. Thus, the targeted maximum likelihood estimator has two important advantages over the Kaplan-Meier estimator: 1) It exploits covariates to improve efficiency, and 2) It is consistent in the presence of informative censoring. These properties are demonstrated through simulation studies. Extensions to the methodology are provided for non randomized post-market safety studies and also for the inclusion of time-dependent covariates

Covariate Adjustment in Randomized Trials with Binary Outcomes: Targeted Maximum Likelihood Estimation

Covariate adjustment using linear models for continuous outcomes in randomized trials has been shown to increase efficiency and power over the unadjusted method in estimating the marginal effect of treatment. However, for binary outcomes, investigators generally rely on the unadjusted estimate as the literature indicates that covariate-adjusted estimates based on logistic regression models are less efficient. The crucial step that has been missing when adjusting for covariates is that one must integrate/average the adjusted estimate over those covariates in order to obtain the marginal effect. We apply the method of targeted maximum likelihood estimation (MLE), as presented in van der Laan and Rubin (2006), to obtain estimators for the marginal effect using covariate adjustment for binary outcomes. We show that the covariate adjustment in randomized trials using logistic regression models can be mapped, by averaging over the covariate(s), to obtain a fully robust and efficient estimator of the marginal effect, which equals the targeted maximum likelihood estimator (MLE). We present simulation studies that show the targeted MLE increases efficiency and power over the unadjusted method, particularly for smaller sample sizes, even when the regression model is mis-specified

Velocity and spatial biases in CDM subhalo distributions

We present a statistical study of substructure within a sample of LCDM clusters and galaxies simulated with up to 25 million particles. With thousands of subhalos per object we can accurately measure their spatial clustering and velocity distribution functions and compare these with observational data. The substructure properties of galactic halos closely resembles those of galaxy clusters with a small scatter in the mass and circular velocity functions. The velocity distribution function is non-Maxwellian and flat topped with a negative kurtosis of about -0.7. Within the virial radius the velocity bias $b=\sigma_{\rm sub}/\sigma_{\rm DM}\sim 1.12 \pm 0.04$, increasing to b > 1.3 within the halo centers. Slow subhalos are much less common, due to physical disruption by gravitational tides early in the merging history. This leads to a spatially anti-biased subhalo distribution that is well fitted by a cored isothermal. Observations of cluster galaxies do not show such biases which we interpret as a limitation of pure dark matter simulations - we estimate that we are missing half of the halo population which has been destroyed by physical overmerging. High resolution hydrodynamical simulations are required to study these issues further. If CDM is correct then the cluster galaxies must survive the tidal field, perhaps due to baryonic inflow during elliptical galaxy formation. Spirals can never exist near the cluster centers and the elliptical galaxies there will have little remaining dark matter. This implies that the morphology-density relation is set {\it before} the cluster forms, rather than a subsequent transformation of disks to S0's by virtue of the cluster environment.Comment: MNRAS accepted version. Due to an error in the initial conditions these simulations have a lower sigma_8 than the published value, 0.7 instead of 0.9. We thank Mike Kuhlen who helped us finding this mistake. See the erratum at http://www-theorie.physik.unizh.ch/~diemand/suberr.pdf . Images and movies available at http://www-theorie.physik.unizh.ch/~diemand/clusters

Multiparametric MR imaging for detection of clinically significant prostate cancer: a validation cohort study with transperineal template prostate mapping as the reference standard.

PURPOSE: To evaluate the diagnostic performance of multiparametric (MP) magnetic resonance (MR) imaging for prostate cancer detection by using transperineal template prostate mapping (TTPM) biopsies as the reference standard and to determine the potential ability of MP MR imaging to identify clinically significant prostate cancer. MATERIALS AND METHODS: Institutional review board exemption was granted by the local research ethics committee for this retrospective study. Included were 64 men (mean age, 62 years [range, 40-76]; mean prostate-specific antigen, 8.2 ng/mL [8.2 μg/L] [range, 2.1-43 ng/mL]), 51 with biopsy-proved cancer and 13 suspected of having clinically significant cancer that was biopsy negative or without prior biopsy. MP MR imaging included T2-weighted, dynamic contrast-enhanced and diffusion-weighted imaging (1.5 T, pelvic phased-array coil). Three radiologists independently reviewed images and were blinded to results of biopsy. Two-by-two tables were derived by using sectors of analysis of four quadrants, two lobes, and one whole prostate. Primary target definition for clinically significant disease necessary to be present within a sector of analysis on TTPM for that sector to be deemed positive was set at Gleason score of 3+4 or more and/or cancer core length involvement of 4 mm or more. Sensitivity, negative predictive value, and negative likelihood ratio were calculated to determine ability of MP MR imaging to rule out cancer. Specificity, positive predictive value, positive likelihood ratio, accuracy (overall fraction correct), and area under receiver operating characteristic curves were also calculated. RESULTS: Twenty-eight percent (71 of 256) of sectors had clinically significant cancer by primary endpoint definition. For primary endpoint definition (≥ 4 mm and/or Gleason score ≥ 3+4), sensitivity, negative predictive value, and negative likelihood ratios were 58%-73%, 84%-89%, and 0.3-0.5, respectively. Specificity, positive predictive value, and positive likelihood ratios were 71%-84%, 49%-63%, and 2.-3.44, respectively. Area under the curve values were 0.73-0.84. CONCLUSION: Results of this study indicate that MP MR imaging has a high negative predictive value to rule out clinically significant prostate cancer and may potentially have clinical use in diagnostic pathways of men at risk