Isomer separation and gas-phase configurations of organoruthenium anticancer complexes: Ion mobility mass spectrometry and modeling

We have used ion mobility-mass spectrometry combined with molecular modeling for the separation and configurational analysis of three low-molecular-weight isomeric organoruthenium anticancer complexes containing ortho-, meta-, or para-terphenyl arene ligands. The isomers were separated using ion mobility based on traveling-wave technology and the experimentally determined collision cross sections were compared to theoretical calculations. Excellent agreement was observed between the experimentally and theoretically derived measurements.     

Avoided critical behavior in dynamically forced wetting

A solid object can be coated by a nonwetting liquid since a receding contact line cannot exceed a critical speed. In this Letter we study the dynamical wetting transition at which a liquid film gets deposited by withdrawing a vertical plate out of a liquid reservoir. It has recently been predicted that this wetting transition is critical with diverging time scales and coincides with the disappearance of stationary menisci. We demonstrate experimentally and theoretically that the transition is due to the formation of a solitary wave, well below the critical point. As a consequence, relaxation times remain finite at threshold. The structure of the liquid deposited on the plate involves a capillary ridge that does not trivially match the Landau-Levich film.     

Silicon core-hollow carbon shell nanocomposites with tunable buffer voids for high capacity anodes of lithium-ion batteries

Silicon core-hollow carbon shell nanocomposites with controllable voids between silicon nanoparticles and hollow carbon shell were easily synthesized by a two-step coating method and exhibited different charge-discharge cyclability as anodes for lithium-ion batteries. The best capacity retention can be achieved with a void/Si volume ratio of approx. 3 due to its appropriate volume change tolerance and maintenance of good electrical contacts.     

Generalized Harmonic Functions and the Dewetting of Thin Films

This paper describes the solvability of Dirichlet problems for Laplace's equation when the boundary data is not smooth enough for the existence of a weak solution in H¹Ω. Scales of spaces of harmonic functions and of boundary traces are defined and the solutions are characterized as limits of classical harmonic functions in special norms. The generalized harmonic functions, and their norms, are defined using series expansions involving harmonic Steklov eigenfunctions on the domain. It is shown that the usual trace operator has a continuous extension to an isometric isomorphism of specific spaces. This provides a characterization of the generalized solutions of harmonic Dirichlet problems. Numerical simulations of a model problem are described. This problem is related to the dewetting of thin films and the associated phenomenology is described.     

Formal Hypothesis Tests for Additive Structure in Random Forests

While statistical learning methods have proved powerful tools for predictive modeling, the black-box nature of the models they produce can severely limit their interpretability and the ability to conduct formal inference. However, the natural structure of ensemble learners like bagged trees and random forests has been shown to admit desirable asymptotic properties when base learners are built with proper subsamples. In this work, we demonstrate that by defining an appropriate grid structure on the covariate space, we may carry out formal hypothesis tests for both variable importance and underlying additive model structure. To our knowledge, these tests represent the first statistical tools for investigating the underlying regression structure in a context such as random forests. We develop notions of total and partial additivity and further demonstrate that testing can be carried out at no additional computational cost by estimating the variance within the process of constructing the ensemble. Furthermore, we propose a novel extension of these testing procedures using random projections to allow for computationally efficient testing procedures that retain high power even when the grid size is much larger than that of the training set.     

Nucleation, growth and retrogrowth of oxidation induced stacking faults in thin silicon-on-insulator

The nucleation, growth, and retrogrowth of stacking faults were investigated for thermally oxidized silicon-on-insulator substrates formed by the separation by implanted oxygen (SIMOX) method. It has been observed that for high oxidation temperatures (T >1150°C) oxidation induced stacking faults (OISFs) undergo a retrogrowth (shrinkage) process at noticeably lower temperatures than in bulk silicon. The retrogrowth process in thin film SIMOX substrates starts at approximately 1190°C for the 2 h thermal oxidations. In this paper, a model for the retrogrowth process is proposed based on the assumption that at high oxidation temperatures vacancies may be injected from the thermal oxide/top silicon interface. We suggest that the vacancy injection reduces the self-interstitial supersaturation and as a direct consequence, attenuates the OISF growth. We also propose that the self-interstitial supersaturation is reduced through point defect recombination inside the silicon overlayer and at the top-silicon/buried-oxide interface where a high density of steps and kink sites are found.     

Reconstructing trees from two point deleted subtrees

The main theorem of this paper states that any tree having at least five vertices can be recovered up to isomorphism from its two point deleted subtrees. The proof makes use of partially labelled trees.