Local deformations of polymers with nonplanar rigid main‐chain internal coordinates

A procedure for local deformation of a polymer by concerted rotation of several main‐chain dihedral angles has been adapted recently to be an elementary move in Monte Carlo simulations. We expand the applicability of the move by generalizing the formalism to allow fixed dihedral angles that sequentially interrupt the rotatable bonds to be nonplanar. The method is applied to the simulation of a small protein in which the dihedral angles of the peptide bonds are allowed to deviate from their ideal values and to the simulation of an RNA hairpin loop in which the main chain (C3′ C4′) bonds that are constrained by the sugar rings are rigid but nonplanar. The move is found to increase the rate at which the systems explore their accessible configuration spaces. The relation of the results to previous studies and possible enhancements of the method are discussed. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 1132–1144, 2000     

Zur schnellen Bestimmung der Kohlens?ure in Rauchgasen

Ohne Zusammenfassung     

Nuclear dimension, $$mathcal{ }$$-stability,and algebraic simplicity for stably projectionless $$C^*$$C∗-algebras

Procesi bundles are certain vector bundles on symplectic resolutions of quotient singularities for wreath-products of the symmetric groups with the Kleinian groups. Roughly speaking, we can define Procesi bundles as bundles on resolutions that provide derived McKay equivalence. In this paper we classify Procesi bundles on resolutions obtained by Hamiltonian reduction and relate the Procesi bundles to the tautological bundles on the resolutions. Our proofs are based on deformation arguments and a connection of Procesi bundles with symplectic reflection algebras.     

Diastereoselective Control of Tetraphenylethene Reactivity by Metal Template Self-Assembly

The reaction of 4,4′,4′′,4′′′-(ethene-1,1,2,2-tetrayl)tetraaniline with 2-pyridinecarboxaldehyde and iron(II) chloride resulted, after aqueous workup, in the diastereoselective formation of an [Fe₂L₃]⁴⁺ triple-stranded helicate structure, irrespective of the stoichiometry employed. The helicate structure was characterized in solution by multinuclear NMR spectroscopy, and in the solid state by single-crystal X-ray crystallography. The reaction of iron(II) tetrafluoroborate or iron(II) bistriflimide with the tetraaniline and 2-pyridinecarboxaldehyde allowed the formation of an [Fe₈L₆]¹⁶⁺ cube when the appropriate stoichiometry was used, but these structures were unstable with respect to hydrolysis. The pendant amine groups on the helicate can be functionalized by reaction with acid chlorides or anhydrides, and the resulting functionalized tetraphenylethene (TPE) units were isolated by the reaction of the helicate with tris(2-aminoethyl)amine. The emission properties of the TPE units were studied in THF/water mixtures, and they were found by dynamic light scattering to self-assemble into large (av. diameter 250 nm) structures.     

Augmenting the immersed boundary method with Radial Basis Functions (RBFs) for the modeling of platelets in hemodynamic flows

We present a new computational method by extending the immersed boundary (IB) method with a geometric model based on parametric radial basis function (RBF) interpolation of the Lagrangian structures. Our specific motivation is the modeling of platelets in hemodynamic flows, although we anticipate that our method will be useful in other applications involving surface elasticity. The efficacy of our new RBF‐IB method is shown through a series of numerical experiments. Specifically, we test the convergence of our method and compare our method with the traditional IB method in terms of computational cost, maximum stable time‐step size, and volume loss. We conclude that the RBF‐IB method has advantages over the traditional IB method and is well‐suited for modeling of platelets in hemodynamic flows. Copyright © 2015 John Wiley & Sons, Ltd.     

Partially Fluorinated Copolymers as Oxygen Sensitive 19F MRI Agents

Effective diagnosis of disease and its progression can be aided by ¹⁹F magnetic resonance imaging (MRI) techniques. Specifically, the inherent sensitivity of the spin–lattice relaxation time (T₁) of ¹⁹F nuclei to oxygen partial pressure makes ¹⁹F MRI an attractive non-invasive approach to quantify tissue oxygenation in a spatiotemporal manner. However, there are only few materials with the adequate sensitivity to be used as oxygen-sensitive ¹⁹F MRI agents at clinically relevant field strengths. Motivated by the limitations in current technologies, we report highly fluorinated monomers that provide a platform approach to realize water-soluble, partially fluorinated copolymers as ¹⁹F MRI agents with the required sensitivity to quantify solution oxygenation at clinically relevant magnetic field strengths. The synthesis of a systematic library of partially fluorinated copolymers enabled a comprehensive evaluation of copolymer structure–property relationships relevant to ¹⁹F MRI. The highest-performing material composition demonstrated a signal-to-noise ratio that corresponded to an apparent ¹⁹F density of 220 mm , which surpasses the threshold of 126 mm ¹⁹F required for visualization on a three Tesla clinical MRI. Furthermore, the T₁ of these high performing materials demonstrated a linear relationship with solution oxygenation, with oxygen sensitivity reaching 240×10⁻⁵ mmHg⁻¹s⁻¹. The relationships between material composition and ¹⁹F MRI performance identified herein suggest general structure–property criteria for the further improvement of modular, water-soluble ¹⁹F MRI agents for quantifying oxygenation in environments relevant to medical imaging.     

Perspectives of cross-sectional scanning tunneling microscopy and spectroscopy for complex oxide physics

Complex oxide heterostructure interfaces have shown novel physical phenomena which do not exist in bulk materials. These heterostructures can be used in the potential applications in the next generation devices and served as the playgrounds for the fundamental physics research. The direct measurements of the interfaces with excellent spatial resolution and physical property information is rather difficult to achieve with the existing tools. Recently developed cross-sectional scanning tunneling microscopy and spectroscopy (XSTM/S) for complex oxide interfaces have proven to be capable of providing local electronic density of states (LDOS) information at the interface with spatial resolution down to nanometer scale. In this perspective, we will briefly introduce the basic idea and some recent achievements in using XSTM/S to study complex oxide interfaces. We will also discuss the future of this technique and the field of the interfacial physics.