Chirooptical and photooptical properties of a novel side-chain azobenzene-containing LC polymer

Abstract  A novel chiral–photochromic side-chain polyacrylate with azobenzene fragments in the side groups has been synthesised. It was shown that the polymer forms a smectic phase and a cholesteric supramolecular helical structure with selective light reflection in IR spectral range. Thin spin-coated films of the polymer were prepared and their photooptical and chirooptical properties were studied in detail. It was found that UV irradiation of the films led to E–Z isomerization of the azobenzene moieties with high conversion, which is dependent on thermal prehistory of the films. Subsequent action of visible light results in partial recovery of the E-isomer content, whereas annealing leads to the full back conversion. Circular dichroism (CD) measurements revealed formation of the helical supramolecular structure even in the initial spin-coated polymer films. The E–Z isomerization induces complete disruption of helical order in non-annealed films of the polymer, whereas in the smectic phase of the annealed film only a significant decrease in CD values was found. In addition, the photoorientation phenomena induced by polarized light were studied. It was shown that polarized light induces linear dichroism in the films provided by azobenzene group orientation and the dichroism is stable at room temperature for a prolonged time. These combined chirooptical and photooptical features of this novel polymer enable one to consider this multifunctional compound as a promising material for photonics and for optical applications. Graphical abstract  

Redetermination of bis[μ3‐1,3,5‐triamino‐1,3,5‐trideoxy‐cis‐inositolato(3–)]tribismuth(III) trichloride hexahydrate

The crystal structure of the title compound, [Bi₃(C₆H₁₂N₃O₃)₂]Cl₃·6H₂O, which was described in the space group R3 [Hegetschweiler, Ghisletta & Gramlich (1993). Inorg. Chem. 32 , 2699–2704], has been redetermined in the revised space group R32 as suggested by Marsh [Acta Cryst. (2002), B 58 , 893–899]. Accordingly, the significant difference in the Bi—N bond distances of 2.43 (2) and 2.71 (1) Å, as noted in the previous study, proved to be an artifact. As a consequence, the [Bi₃(H₋₃taci)₂]Cl_6/3 entity (taci is 1,3,5‐triamino‐1,3,5‐trideoxy‐cis‐inositol) adopts D₃ symmetry and the three Bi atoms lie on C₂ axes with equal Bi—N bond distances of 2.636 (3) Å.     

A simple GUI for modeling the optical properties of single metal nanoparticles

We present a graphical user interface, based on the modified long-wavelength approximation, to compute the optical properties of single metal nanoparticles of ellipsoidal geometry (spheres, rods, and disks). The user-friendly interface allows one to readily gauge the accuracy of results obtained using the modified long-wavelength approximation. For spherical particles, up to 10-nm diameter, we confirm that our approach yields an exact correspondence with Mie theory, and gives an approximation error of less than 15% for gold (silver) particles with diameters approaching 40 nm (26 nm). Results are shown to be sensitive to the source data for the optical constants for a given material. The modular nature of the simulation platform provides a quick and intuitive guide for optical characterization experiments.     

A new high precision measurement of the muonium hyperfine structure interval Δv1

At LAMPF we have observed muonium resonance curves in low pressure argon and krypton at very weak magnetic field using two line narrowing techniques, and have obtained Δv = 4 463 302.2 (1.4) kHz (0.3 ppm). This is the most precise value of Δν yet quoted, and from it we obtain improved values for the muon magnetic moment and mass: $\text{μ}{}_{\mathrm{\mu }}{}_{\mathrm{<mtext>p</mtext>}}\text{= 3.183 329 9 (25) (0.8}\text{ppm}\text{);}\text{m}{}_{\mathrm{\mu }}\text{m}{}_{\mathrm{<mtext>e</mtext>}}\text{= 206.769 27 (17) (0.8}\text{ppm}\text{)}$.     

Reactivation of aged model Pd/Ce0.68Zr0.32O2 three-way catalyst by high temperature oxidising treatment

A deactivated (aged under redox-cycled model TWC feed-stream) Pd/Ce(0.68)Zr(0.32)O(2) catalyst is remarkably reactivated when subjected to a high temperature oxidising treatment whereas this effect is only marginal for Pd/Al(2)O(3), which indicates the key role of such treatment in restoring the Pd-Ce(0.68)Zr(0.32)O(2) interactions leading to highly active catalysts.     

Effect of side-chain disorder on the electronic structure of proteins

The influence of side-chain disorder on the electronic structure of proteins has been investigated in the case of polypeptides containing two or three different amino acid residues. It has been found that due to the different potentials of different side-chain groups, the original valence and conduction bands of the homopolypeptides are split into narrow bands. The comparison of the densities of electronic states in simple homopolypeptides and in composite polymers shows that new forbidden regions in the energy spectrum of proteins may develop. The consequences of these effects for the semiconductive properties of proteins are discussed.     

Search for lepton flavor violation in K+ decays into a charged pion and two leptons

A search for lepton flavor violating decays, K+ --> mu+ mu+ pi-, K+ --> e+ e+ pi-, K+ --> pi+ e+ mu-, K+ --> mu+ e+ pi-, and pi0 --> e+ mu-, was performed using the data collected in Experiment E865 at the Brookhaven Alternating Gradient Synchrotron. No signal was found in any of the decay modes. At the 90% confidence level, the branching ratios are less than 3.0x10(-9), 6.4x10(-10), 5. 2x10(-10), 5.0x10(-10), and 3.4x10(-9), respectively.