The Space of Measurement Outcomes as a Spectral Invariant for Non-Commutative Algebras

The recently developed technique of Bohrification associates to a (unital) C*-algebra A

Hexagonal YMnO3

The crystal structure of hexagonal yttrium trioxomanganate has been determined at room temperature and at 180 K. It is isomorphous with LuMnO₃. The Mn displacement vector has a frustrated component in the ab plane and a ferroelectric part along the c axis. The net ferroelectricity is zero due to inversion twinning, with 1:1 twin fractions.     

Anchoring Supramolecular Polymers to Human Red Blood Cells by Combining Dynamic Covalent and Non-Covalent Chemistries

Understanding cell/material interactions is essential to design functional cell-responsive materials. While the scientific literature abounds with formulations of biomimetic materials, only a fraction of them focused on mechanisms of the molecular interactions between cells and material. To provide new knowledge on the strategies for materials/cell recognition and binding, supramolecular benzene-1,3,5-tricarboxamide copolymers bearing benzoxaborole moieties are anchored on the surface of human erythrocytes via benzoxaborole/sialic-acid binding. This interaction based on both dynamic covalent and non-covalent chemistries is visualized in real time by means of total internal reflection fluorescence microscopy. Exploiting this imaging method, we observe that the functional copolymers specifically interact with the cell surface. An optimal fiber affinity towards the cells as a function of benzoxaborole concentration demonstrates the crucial role of multivalency in these cell/material interactions.     

Note on integer-valued bilinear time series models

This note reconsiders the nonnegative integer-valued bilinear processes introduced by Doukhan et al. [Doukhan, P., Latour, A., Oraichi, D., 2006. A simple integer-valued bilinear time series model. Adv. Appl. Prob. 38, 559–578]. Using a hidden Markov argument, we extend their result of the existence of a stationary solution for the INBL(1, 0, 1, 1) process to the class of superdiagonal models. Our approach also yields improved parameter restrictions for several moment conditions compared to the ones in [Doukhan, P., Latour, A., Oraichi, D., 2006. A simple integer-valued bilinear time series model. Adv. Appl. Prob. 38, 559–578].     

Expanding the supramolecular polymer LEGO system: Nitroxide‐mediated living free‐radical polymerization as a tool for mono‐ and telechelic polystyrenes

Nitroxide‐mediated, controlled living radical polymerization was employed to introduce terpyridine ligands at one or two chain ends of polystyrene. For this purpose, a unimolecular initiator bearing both a terpyridine ligand as well as a mediating nitroxide was synthesized and used for the controlled polymerization of styrene. Moreover, a maleimide‐functionalized terpyridine was prepared in order to synthesize telechelic polymers, utilizing nitroxide substitution reactions. Kinetic studies of the polymerization of styrene were carried out. In all polymerizations, special attention was focused on the retention of end‐group functionality, in light of the effects of autoinitiation and autopolymerization. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4016–4027, 2004     

Low energy structures of gold nanoclusters in the size range 3–38 atoms

Using a combination of first principles calculations and empirical potentials we have undertaken a systematic study of the low energy structures of gold nanoclusters containing from 3 to 38 atoms. A Lennard-Jones and many-body potential have been used in the empirical calculations, while the first principles calculations employ an atomic orbital, density functional technique. For the smaller clusters (n=3–5) the potential energy surface has been mapped at the ab initio level and for larger clusters an empirical potential was first used to identify low energy candidates which were then optimised with full ab initio calculations. At the DFT-LDA level, planar structures persist up to six atoms and are considerably more stable than the cage structures by more than 0.1 eV/atom. The difference in ab initio energy between the most stable planar and cage structures for seven atoms is only 0.04 eV/atom. For larger clusters there are generally a number of minima in the potential energy surface lying very close in energy. Furthermore our calculations do not predict ordered structures for the magic numbers n=13 and 38. They do predict the ordered tetrahedral structure for n=20. The results of the calculations show that gold nanoclusters in this size range are mainly disordered and will likely exist in a range of structures at room temperature.     

Cylindrical micelles from the aqueous self-assembly of an amphiphilic poly(ethylene oxide)-b-poly(ferrocenylsilane) (PEO-b-PFS) block copolymer with a metallo-supramolecular linker at the block junction

A supramolecular AB diblock copolymer has been prepared by the sequential self-assembly of terpyridine end-functionalized polymer blocks by using Ru(III)/Ru(II) chemistry. By this synthetic strategy a hydrophobic poly(ferrocenylsilane) (PFS) was attached to a hydrophilic poly(ethylene oxide) (PEO) block to give an amphiphilic metallo-supramolecular diblock copolymer (PEO/PFS block ratio 6:1). This compound was used to form micelles in water that were characterized by a combination of dynamic and static light scattering, transmission electron microscopy, and atomic force microscopy. These complementary techniques showed that the copolymers investigated form rod-like micelles in water; the micelles have a constant diameter but are rather polydisperse in length, and light scattering measurements indicate that they are flexible. Crystallization of the PFS in these micelles was observed by differential scanning calorimetry, and is thought to be the key behind the formation of rod-like structures. The cylindrical micelles can be cleaved into smaller rods whenever the temperature of the solution is increased or they are exposed to ultrasound.     

Characterization of Carotenoid Triplet States in the Light-Harvesting Complex B800–850from the Purple Bacterium Rubrivivax gelationsus

The carotenoid triplet states in the light-harvesting complex B800–850from purple bacterium Rubrivivax gelatinosus were characterized by absorption-detected magnetic resonance in zero magnetic field (ADMR) spectroscopy. Detailed HPLC analysis of carotenoids from B800–850demonstrated the presence of several carotenoids bound to the complex: the major ones are hydroxyspheroidene and spheroidene (together 80%), followed by neurosporene and hydroxyneurosporene (7%), spheroidenone and hydroxyspheroidenone (7.5%) and two other minor carotenoids that could be 3,4-dihydrospheroidenone and 3,4-dihydrohydroxyspheroidenone (5.5%). Three triplet states originating from carotenoids present in the B800–850were observed. The identical T-S spectra recorded at selectively chosen 2|E| transitions of carotenoids indicated that all these triplet states can be attributed to three different populations of one carotenoid family, probably to spheroidene and to hydroxyspheroidene, with different out-of-plane distortions of their polyene chain due to a different protein environment. Triplet states of the neurosporene and the spheroidenone families are probably not observed because of the low signal amplitude.     

Playing LEGO with macromolecules: Design,synthesis, and self‐organization with metal complexes

Several synthetic strategies for the incorporation of supramolecular binding units into polymers are described. Specifically, terpyridine ligands have been introduced into polymers in such a way that they are distributed either randomly throughout the polymer backbone or at the chain end(s). Two terpyridine ligands form octahedral complexes with a variety of transition‐metal ions, each having different properties. Some general statements regarding metal complex stability are presented as well as a special case representing the selective construction of heteroleptic terpyridine complexes. This leads to a kind of LEGO system for connecting and disconnecting the polymer blocks via metal complexes. Metallo‐supramolecular block copolymers, graft copolymers, and chain‐extended polymers can be designed and prepared with the principles described. Once the design parameters have been derived, thorough control over the final material and its properties can be gained. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1413–1427, 2003