Inelastic proton scattering from Ba and Sm at 30 MeV

Measurements of the inelastic scattering of 30 MeV protons from ¹³⁸Ba and ¹⁴⁴Sm have been carried out with 7–10 keV energy resolution. Differential cross sections were measured for levels up through 3.4 MeV excitation energy. For most of these states J^π assignments are suggested on the basis of angular distributions distinctly characteristic of angular momentum transfer L = 2, 3, 4,or 6.     

Structural investigation of (CuI)0.45–(Ag2WO4)0.55 solid electrolyte using X-ray photoelectron and laser Raman spectroscopies

X-ray photoelectron spectroscopy (XPS) and laser Raman scattering (LRS) techniques have been employed to investigate the structure of amorphous (CuI)_0.45–(Ag₂WO₄)_0.55 solid electrolyte sample. XPS results reveal the presence of both Cu⁺ and Cu²⁺ ions whereas tungsten is found to exist only in the oxidation state of +6. The deconvolution of the O 1s spectrum into non-bridging and bridging oxygen atoms in conjunction with the laser Raman analysis tend to show that the amorphous (CuI)_0.45–(Ag₂WO₄)_0.55 solid electrolyte sample is composed mostly of octahedral WO₆ units that probably form [W₄O₁₆]⁸⁻ tetramer clusters, the existence of which is unique in the case of oxyhalide glasses.     

An electric bottle for colloids

Particle concentration is a dominant control parameter for colloids and other soft matter systems. We demonstrate a simple technique, "dielectrophoretic equilibrium," implemented as an "electric bottle," a planar capacitor in a larger volume. The uniform field in the capacitor traps particles in this force-free region at a higher density than in the zero field regions outside. We show how the technique measures the equation of state and we initiate and grow colloidal crystals. "Dielectrophoretic equilibria" enable the study of a complete concentration-dependent phase diagram from a single microscopic sample, obviating the previous need for preparing a large number of samples.     

Advances in methods and algorithms in a modern quantum chemistry program package

Advances in theory and algorithms for electronic structure calculations must be incorporated into program packages to enable them to become routinely used by the broader chemical community. This work reviews advances made over the past five years or so that constitute the major improvements contained in a new release of the Q-Chem quantum chemistry package, together with illustrative timings and applications. Specific developments discussed include fast methods for density functional theory calculations, linear scaling evaluation of energies, NMR chemical shifts and electric properties, fast auxiliary basis function methods for correlated energies and gradients, equation-of-motion coupled cluster methods for ground and excited states, geminal wavefunctions, embedding methods and techniques for exploring potential energy surfaces.     

Critical particle size for fractionation by deterministic lateral displacement

The fractionation of small particles in a liquid based on their size in a micropost array by deterministic lateral displacement was recently demonstrated with unprecedented resolution (L. R. Huang, E. C. Cox, R. H. Austin and J. C. Sturm, Science, 2004, 304, 987-990, ). In this paper, we present a model of how the critical particle size for fractionation depends on the micropost geometry, depending specifically on the gap between posts, the offset of posts in one row with respect to another, and whether the fluid is driven by hydrodynamics or by electroosmosis. In general the critical particle diameter is much smaller than the gap, which prevents clogging. The model is supported by data with particles from 2.3 to 22 microm.     

Analysis and prediction of combinatorial chemistry synthesis and screening data

The goal of combinatorial chemistry is to simultaneously synthesize sets of compounds possessing properties that are then distinguished through screening. As the size of a compound set increases, data analysis becomes more challenging. Analysis of Variance (ANOVA) is an accepted statistical method that offers a straightforward solution to this problem. Two steps encountered by combinatorial scientists appear well suited to ANOVA: the prediction of synthetic outcomes (purity and yield) of set members and the analysis of screening data to identify combinations of reagent inputs that result in molecules with a desired property. To illustrate, a subset of a combinatorial array, referred to as a reaction rehearsal set, is evaluated to create a model predictive of the individual synthetic outcomes of the full matrix. In a second exercise, the biochemical screening data obtained from a combinatorial library is analyzed to identify reagent interactions that result in molecules possessing the sought activity.     

Cluster Consensus of Nonlinearly Coupled Multi-Agent Systems in Directed Graphs

We investigate the cluster consensus problem in directed networks of nonlinearly coupled multi-agent systems by using pinning control. Depending on the community structure generated by the group partition of the underlying digraph, various clusters can be made coherently independent by applying feedback injections to a fraction of the agents. Sufficient conditions for cluster consensus are obtained using algebraic graph theory and matrix theory and some simulations results are included to illustrate the method.     

Deducing the multidimensional Szemerédi theorem from an infinitary removal lemma

We offer a new proof of the Furstenberg-Katznelson multiple recurrence theorem for several commuting probability-preserving transformations T ₁, T ₂, …, T _d : ℤ ↷ (X, ∑, μ) ([6]), and so, via the Furstenberg correspondence principle introduced in [5], a new proof of the multi-dimensional Szemerédi Theorem. We bypass the careful manipulation of certain towers of factors of a probability-preserving system that underlies the Furstenberg-Katznelson analysis, instead modifying an approach recently developed in [1] to pass to a large extension of our original system in which this analysis greatly simplifies. The proof is then completed using an adaptation of arguments developed by Tao in [13] for his study of an infinitary analog of the hypergraph removal lemma. In a sense, this addresses the difficulty, highlighted by Tao, of establishing a direct connection between his infinitary, probabilistic approach to the hypergraph removal lemma and the infinitary, ergodic-theoretic approach to Szemerédi’s Theorem set in motion by Furstenberg [5].