Nondestructive compositional depth profiling using variable‐kinetic energy hard X‐ray photoelectron spectroscopy and maximum entropy regularization

We discuss the calculation of nondestructive compositional depth profiles from regularization of variable kinetic energy hard X‐ray photoelectron spectroscopy (VKE‐XPS) data, adapting techniques developed for angle‐resolved XPS. Simulated TiO₂/Si film structures are analyzed to demonstrate the applicability of regularization techniques to the VKE‐XPS data and to determine the optimum choice of regularization function and the number of data points. We find that using a maximum entropy‐like method, when the initial model/prior thickness is similar to the simulated film thickness, provides the best results for cases where prior knowledge of the sample exists. For the simple structures analyzed, we find that only five kinetic energy spectra are necessary to provide a good fit to the data, although in general, the number of spectra will depend on the sample structure and noisiness of the data. The maximum entropy‐like algorithm is then applied to two physical films of TiO₂ deposited on Si. Results suggest interfacial intermixing. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.     

GUIDED WAVES IN MULTILAYERED PLATES: AN IMPROVED ORTHOGONAL POLYNOMIAL APPROACH

Conventional orthogonal polynomial approach can solve the multilayered plate only when the material properties of two adjacent layers do not change significantly. This paper de- veloped an improved orthogonal polynomial approach to solve wave propagation in multilayered plates with very dissimilar material properties. Through numerical comparisons among the exact solution, the results from the conventional polynomial approach and from the improved poly- nomial approach, the validity of the improved polynomial approach is illustrated. Finally, it is shown that the conventional polynomial approach can not yield correct continuous normal stress profiles. The improved orthogonul polynomial approach has overcome this drawback.     

Energy,fluence and temperature dependence of MeV nitrogen implantation profiles in steel

Abstract

1 to 2 MeV nitrogen (N⁺ and N₂ ⁺) ions were implanted at high fluences in stainless steel, and their depth distributions were measured subsequently by Rutherford backscattering and thermal neutron depth profiling. The range profiles were broader than theoretically expected. With increasing fluence, deviations from ballistic computer codes increase. These deviations can well be described by the assumption of radiation enhanced diffusion for which a simple analytical model is presented. The thermal mobility shows a different behavior for low, and for high implanted fluences.     

Vibrational Dynamics and Heat Capacity of Trans‐1,4‐Polyisoprene (α‐Form)

Vibrational dynamics of the α‐polymorphic form of trans‐1‐4‐polyisoprene is described using Higg's method and the Urey‐Bradley force field. Characteristic features of dispersion profiles such as repulsion and bunching are reported. A comparison with the β‐form is presented and possible reasons for variation in heat capacity are discussed.     

Fabrication techniques for high-quality optical fibers

Various vapor deposition processes are being used to manufacture optical fibers in different parts of the world. This paper provides an introduction to the common vapor deposition technology, reviews the different processes, and compares them in terms of performance and cost potential.     

Influence of polymer conformation on the entrance length in capillary flow

An analysis of the flow of polymer solutions through capillaries by means of pressure profiles was performed in this work. The experiments were carried out with aqueous solutions of flexible and semirigid macromolecules, Polyox and Xanthan respectively. The influence of the macromolecules' conformation on the flow field development is reflected on the different magnitudes of the entry length, being of the order of 60 diameters for the solutions of rigid macromolecules, and of the order of 10 diameters for flexible ones. In addition, the calculated end effects were larger for the rigid macromolecules than for the flexible ones. From these results, it is found that an increase in the entrance length is observed when the pseudoplastic behavior of the polymer solutions is increased.Dedicated to Prof. Dr. J. Meissner on the occasion of his retirement from the chair of Polymer Physics at the Eidgenössische Technische Hochschule (ETH) Zürich, Switzerland     

Electron momentum distributions and compton profiles of some molecules with FSGO model

The electron momentum distributions and the Compton profiles (within the impulse approximation) of H₂, LiH, methane, water, acetylene, ethylene, ethane cyclopropane and cyclobutane have been calculated using the floating spherical Gaussian orbital (FSGO) wavefunctions. The agreement of the single-FSGO Compton profiles with the corresponding experimental or the Hartree-Fock (HF-SCF) theoretical ones is fairly good in most of the cases examined. The advantages and drawbacks of using the FSGO model for the calculation of Compton profiles are discussed.     

Searching Inhibitors of Adenosine Kinase by Simulation Methods

Searching new inhibitors of adenosine kinase （AK） is still drawing attention of experimental scientists. A better and solid model is here proposed by means of simulation methods from different ways, the direct analysis of receptor itself, the conventional 3D-QSAR methods and the integration of docking method and the conventional QSAR analysis.     

Gaussian mapping of chemical fragments in ligand binding sites

We present a new approach to automatically define a quasi-optimal minimal set of pharmacophoric points mapping the interaction properties of a user-defined ligand binding site. The method is based on a fitting algorithm where a grid of sampled interaction energies of the target protein with small chemical fragments in the binding site is approximated by a linear expansion of Gaussian functions. A heuristic approximation selects from this expansion the smallest possible set of Gaussians required to describe the interaction properties of the binding site within a prespecified accuracy. We have evaluated the performance of the approach by comparing the computed Gaussians with the positions of aromatic sites found in experimental protein-ligand complexes. For a set of 53 complexes, good correspondence is found in general. At a 95% significance level, approximately 65% of the predicted interaction points have an aromatic binding site within 1.5 A. We then studied the utility of these points in docking using the program DOCK. Short docking times, with an average of approximately 0.18 s per conformer, are obtained, while retaining, both for rigid and flexible docking, the ability to sample native-like binding modes for the ligand. An average 4-5-fold speed-up in docking times and a similar success rate is estimated with respect to the standard DOCK protocol.