Focused Information Criterion for Restricted Mean Survival Times: Non-Parametric or Parametric Estimators

Restricted Mean Survival Time (RMST), the average time without an event of interest until a specific time point, is a model-free, easy to interpret statistic. The heavy reliance on non-parametric or semi-parametric methods in the survival analysis has drawn criticism, due to the loss of efficacy compared to parametric methods. This assumes that the parametric family used is the true one, otherwise the gain in efficacy might be lost to interpretability problems due to bias. The Focused Information Criterion (FIC) considers the trade-off between bias and variance and offers an objective framework for the selection of the optimal non-parametric or parametric estimator for scalar statistics. Herein, we present the FIC framework for the selection of the RMST estimator with the best bias-variance trade-off. The aim is not to identify the true underling distribution that generated the data, but to identify families of distributions that best approximate this process. Through simulation studies and theoretical reasoning, we highlight the effect of censoring on the performance of FIC. Applicability is illustrated with a real life example. Censoring has a non-linear effect on FICs performance that can be traced back to the asymptotic relative efficiency of the estimators. FICs performance is sample size dependent; however, with censoring percentages common in practical applications FIC selects the true model at a nominal probability (0.843) even with small or moderate sample sizes.     

Magnetite (Fe3O4): a new variant of relaxor multiferroic?

The electric polarization, dielectric permittivity, magnetoelectric effect, heat capacity, magnetization and ac susceptibility of magnetite films and polycrystals were investigated. The electric polarization of magnetite films with saturation values between 4 and 8 μC cm(-2) was found to vanish between 32 and 38 K, but in polycrystals no phase transition was detected in this range by heat capacity. Both types of samples showed magnetoelectric effects at low temperatures below a frequency-dependent crossover. This is interpreted as arising from multiferroic relaxor behavior.     

Phosphaalkenyl germylenes and their gold, tungsten and molybdenum complexes

The new bis(phosphaalkenyl) germanium(II) compound (NHC)Ge(CCl=PMes*)(2) reacts with L(2)M(CO)(4) (M = Mo, W) to give bidentate complexes with an unexpected coordinating behaviour involving the Ge(II) centre and one phosphorus atom, and with AuI or Me(2)SAuCl to afford the monodentate complexes coordinated at the germanium(II) atom.     

Unusual surface mass changes in the course of the oxygen reduction reaction on platinum and their explanation by using a kinetic model

An unusual change of the surface mass with time has been observed during the oxygen reduction reaction on Pt using chronopotentiometry and simultaneous electrochemical quartz crystal nanobalance measurements. A simplified kinetic model of Damjanovic and Brusic, which involves two electrochemical and a chemical step, was analyzed using phase plane analysis. The theoretical analysis predicted that bistability might occur in this system at a certain set of parameter values. The mathematical simulation of the different trajectories explained well the strong influence of the starting potential and the current density on the change of the surface mass observed. Evidence was found that the surface coverage can increase at lower potentials, which can lead to the formation of hydrogen peroxide even if it is energetically unfavorable.     

Atomic focusing by quantum fields: Entanglement properties

The coherent manipulation of the atomic matter waves is of great interest both in science and technology. In order to study how an atom optic device alters the coherence of an atomic beam, we consider the quantum lens proposed by Averbukh et al. [1] to show the discrete nature of the electromagnetic field. We extend the analysis of this quantum lens to the study of another essentially quantum property present in the focusing process, i.e., the atom–field entanglement, and show how the initial atomic coherence and purity are affected by the entanglement. The dynamics of this process is obtained in closed form. We calculate the beam quality factor and the trace of the square of the reduced density matrix as a function of the average photon number in order to analyze the coherence and purity of the atomic beam during the focusing process.     

Regularization independent analysis of the origin of two loop contributions to N=1 Super Yang–Mills beta function

We present both an ultraviolet and an infrared regularization independent analysis in a symmetry preserving framework for the N=1 Super Yang–Mills beta function to two loop order. We show explicitly that off-shell infrared divergences as well as the overall two loop ultraviolet divergence cancel out, whilst the beta function receives contributions of infrared modes.     

Variational quantum mechanical and active database approaches to the rotational-vibrational spectroscopy of ketene, H2CCO

A variational quantum mechanical protocol is presented for the computation of rovibrational energy levels of semirigid molecules using discrete variable representation of the Eckart-Watson Hamiltonian, a complete, "exact" inclusion of the potential energy surface, and selection of a vibrational subspace. Molecular symmetry is exploited via a symmetry-adapted Lanczos algorithm. Besides symmetry labels, zeroth-order rigid-rotor and harmonic-oscillator quantum numbers are employed to characterize the computed rovibrational states. Using the computational molecular spectroscopy algorithm presented, a large number of rovibrational states, up to J = 50, of the ground electronic state of the parent isotopologue of ketene, H(2) (12)C=(12)C=(16)O, were computed and characterized. Based on 12 references, altogether 3982 measured and assigned rovibrational transitions of H(2) (12)C=(12)C=(16)O have been collected, from which 3194 were validated. These transitions form two spectroscopic networks (SN). The ortho and the para SNs contain 2489 and 705 validated transitions and 1251 and 471 validated energy levels, respectively. The computed energy levels are compared with energy levels obtained, up to J = 41, via an inversion protocol based on this collection of validated measured rovibrational transitions. The accurate inverted energy levels allow new assignments to be proposed. Some regularities and irregularities in the rovibrational spectrum of ketene are elucidated.     

Structurally original oxathioethers macrocycles containing an exocyclic double-bond: synthesis,characterization, reactivity,and coordination

New oxathioethers macrocycles have been synthesized and characterized. Each macrocycle consists in structurally defined ether and thioether moieties and an exocyclic double-bond (2a–c) or a hydroxymethyl group (3a–c). Macrocycles (2a–c) have been synthesized by reaction of dianions of thioethers diols (1a–c) with 3-chloro-2-chloromethylprop-1-ene. Their hydroboration/oxidation led to corresponding primary alcohols (3a–c). Structures of compounds (2b) and (3a) have been determined by X-ray diffraction. The reactivity of the hydroxyl group allowed the preparation of oxathioethers macrocycles bearing a polyether chain or a benzyl group (4a,b) and the synthesis of new bicyclic sandwich-type compounds (5a,b). The ability of these functionalized macrocycles to coordinate to palladium has been investigated.     

New Halo Compounds of Si,P, As,AND Sb Bearing a Bulky Substituted Fluorenyl Group

New halo compounds of Si, P, As, and Sb, potential precursors of doubly-bonded derivatives of these elements, have been synthesized: dichloro-and difluorosilanes 2–6 bearing a methylfluorenyl group and a second substituent of various size (Me, Ph, Mes, R₂CMe); dichlorophosphines 13 and 14, fluoro- and difluoroarsines 15 and 16 and fluorostibine 17, substituted by the diphenyl (or dimesityl) phosphinofluorenyl group. Phosphine oxide and sulfide 9 and 10 also have been prepared.