Coordinative and electrostatic forces in action: from the design of differential chromogenic anion sensors to selective carboxylate recognition

A new family of differential chromogenic anion chemosensors is described based on anilinopyridine-metal cation coordinative signalling ensembles.     

Particle connectedness and cluster formation in sequential depositions of particles: integral-equation theory

We applied the integral-equation theory to the connectedness problem. The method originally applied to the study of continuum percolation in various equilibrium systems was modified for our sequential quenching model, a particular limit of an irreversible adsorption. The development of the theory based on the (quenched-annealed) binary-mixture approximation includes the Ornstein-Zernike equation, the Percus-Yevick closure, and an additional term involving the three-body connectedness function. This function is simplified by introducing a Kirkwood-like superposition approximation. We studied the three-dimensional (3D) system of randomly placed spheres and 2D systems of square-well particles, both with a narrow and with a wide well. The results from our integral-equation theory are in good accordance with simulation results within a certain range of densities.     

An improved algorithm for selecting <Emphasis Type="Italic">p</Emphasis> items with uncertain returns according to the minmax-regret criterion

We consider the problem of selecting a subset of p investments of maximum total return out of a set of n available investments with uncertain returns, where uncertainty is represented by interval estimates for the returns, and the minmax regret objective is used. We develop an algorithm that solves this problem in O(min{p,n–p}n) time. This improves the previously known complexity O(min{p,n–p}²n).This research has been supported by the Spanish Science and Technology Ministry and FEDER Grant No. BFM2002-04525-C02-02.Received: October 2002 / Accepted: September 2003     

Reconstruction of protein structures from a vectorial representation

We show that the contact map of the native structure of globular proteins can be reconstructed starting from the sole knowledge of the contact map's principal eigenvector, and present an exact algorithm for this purpose. Our algorithm yields a unique contact map for all 221 globular structures of PDBselect25 of length N相似文献   

Construction of hydrolytically-degradable thin films via layer-by-layer deposition of degradable polyelectrolytes

Hydrolytically degradable, multilayered films ranging from 10 to 100 nm have been constructed by the layer-by-layer deposition of degradable polycations and oppositely charged polyanions. Polycations play dual roles in these systems, serving as structural components of the film as well as transient elements designed to trigger release; polyanions serve as structural components and as entities to be released or delivered. The films erode in a controlled manner under physiological conditions and are suitable for the incorporation and subsequent controlled release of functional polyanions such as DNA.     

Perimeter, Diameter and Area of Convex Sets in the Hyperbolic Plane

The paper studies the relation between the asymptotic valuesof the ratios area/length (F/L) and diameter/length (D/L) ofa sequence of convex sets expanding over the whole hyperbolicplane. It is known that F/L goes to a value between 0 and 1depending on the shape of the contour. In the paper, it is firstof all seen that D/L has limit value between 0 and 1/2 in strongcontrast with the euclidean situation in which the lower boundis 1/ (D/L = 1/ if and only if the convex set has constant width).Moreover, it is shown that, as the limit of D/L approaches 1/2,the possible limit values of F/L reduce. Examples of all possiblelimits F/L and D/L are given.     

Development of a Kinetic Model for Thermal Crosslinking of Rubbery Polymers

Summary: A kinetic model for the thermal crosslinking of rubbery polymers is presented. The reaction mechanism used to develop the model includes thermal radical generation producing a polymeric radical and a primary radical, crosslinking from attack of a polymer radical to any inactive polymer molecule, bimolecular radical termination among chains of any degree of branching, and radical termination between a polymer radical and a primary radical from the thermal radical generation. The overall polymer population is divided into “generations”, which are defined in terms of the number of primary (linear) chains of original rubbery polymer attached to the polymer molecule. Mass balances for each generation are written down, and expressions to calculate fraction of branched molecules, gel fraction, and number and weight average chain lengths are derived. Model simulations, parameter sensitivity analyses and preliminary parameter estimation studies are presented, taking the thermal crosslinking of linear polybutadiene as a case study.

Development of a kinetic model for thermal crosslinking of rubbery polymers: reaction mechanism, model equations and parameter sensitivity analyses.     

The Toda System and Clustering Interfaces in the Allen–Cahn equation

We consider the Allen–Cahn equation in a bounded, smooth domain Ω in , under zero Neumann boundary conditions, where is a small parameter. Let Γ₀ be a segment contained in Ω, connecting orthogonally the boundary. Under certain nondegeneracy and nonminimality assumptions for Γ₀, satisfied for instance by the short axis in an ellipse, we construct, for any given N ≥ 1, a solution exhibiting N transition layers whose mutual distances are and which collapse onto Γ₀ as . Asymptotic location of these interfaces is governed by a Toda-type system and yields in the limit broken lines with an angle at a common height and at main order cutting orthogonally the boundary.     

[1‐Me‐1‐closo‐SnB11H11]− as a potential weakly coordinating anion: Synthesis of Rh(PPh3)2(1‐Me‐closo‐SnB11H11) and comparisons with Rh(PR3)2 (1‐H‐closo‐CB11 H11)

The closo‐stannaborane salt [Rh(PPh₃)₂‐(nbd)][1‐Me‐1‐closo‐SnB₁₁H₁₁] reacts with H₂ in CH₂ Cl₂ solution to afford the contact ion‐pair Rh(PPh₃)₂(1‐Me‐closo‐SnB₁₁H₁₁), which has been characterized in solution and the solid state by X‐ray diffraction. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:174–180, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20218     

Discrete mechanics and control on Lie groupoids

The first order optimality conditions for discrete-time optimal control problems defined on Lie groupoids are found, and they are expressed in terms of composability in a groupoid. Some examples are shown. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)