A multiswitchable poly(terthiophene) bearing a spiropyran functionality: understanding photo- and electrochemical control

An electroactive nitrospiropyran-substituted polyterthiophene, poly(2-(3,3'-dimethylindoline-6'-nitrobenzospiropyranyl)ethyl 4,4'-didecyloxy-2,2':5',2'-terthiophene-3'-acetate), has been synthesized for the first time. The spiropyran, incorporated into the polymer backbone by covalent attachment to the alkoxyterthiophene monomer units, leads to multiple colored states as a result of both photochemical and electrochemical isomerization of the spiropyran moiety to merocyanine forms as well as electrochemical oxidation of the polyterthiophene backbone and the merocyanine substituents. While electrochemical polymerization of the terthiophene monomer can take place without oxidation of the spiropyran, increasing the oxidation potential leads to complex electrochemistry that clearly involves this substituent. To understand this complex behavior, the first detailed electrochemical study of the oxidation of the precursor spiropyran, 1-(2-hydroxyethyl)-3,3-dimethylindoline-6'-nitrobenzospiropyran, was undertaken, showing that, in solution, an irreversible electrochemical oxidation of the spiropyran occurs leading to reversible redox behavior of at least two merocyanine isomers. With these insights, an extensive electrochemical and spectroelectrochemical study of the nitrospiropyran-substituted polyterthiophene films reveals an initial irreversible electrochemical oxidative ring-opening of the spiropyran to oxidized merocyanine. Subsequent reduction and cyclic voltammetry of the resulting nitromerocyanine-substituted polyterthiophene film gives rise to the formation of both merocyanine π-dimers or oligomers and π-radical cation dimers, between polymer chains. Although merocyanine formation is not electrochemically reversible, the spiropyran can be photochemically regenerated, through irradiation with visible light. Subsequent electrochemical oxidation of the nitrospiropyran-substituted polymer reduces the efficiency of the spiropyran to merocyanine isomerization, providing electrochemical control over the polymer properties. SEM and AFM images support the conclusion that the bulky spiropyran substituent is electrochemically isomerized to the planar merocyanine moiety, affording a smoother polymer film. The conductivity of the freestanding polymer film was found to be 0.4 S cm(-1).     

THE SINGULARLY PERTURBED NONLOCAL REACTION DIFFUSION SYSTEM

In this paper the singularly perturbed initial boundary value problems for the nonlocal reaction diffusion system are considered. Unsing the iteration method and the comparison theorem, the existence, uniqueness and its asymptotic behavior of solution for the problem are studied.     

Relativistic mean field and some recent applications

The essentials of the Relativistic Mean Field (RMF) theory and some of its recent applications are presented. The explicit calculations are carried out for a few selected isotopic, isotonic and isobaric chains of nuclei covering the entire periodic table. The calculated ground state properties are found to be in good agreement with the corresponding experiment: the binding energies are reproduced within 0.25%, on average, and the charge radii differ only in the second decimal place of fermi. The relativistic origin of the pseudo-spin symmetry is briefly discussed. The density distributions obtained, are found to be in good agreement with the experiment (where available). The peripheral factor, the ratio of neutron and proton densities on the nuclear periphery, extracted in the anti-proton annihilation experiments are well reproduced. The RMF densities are used to calculate the reaction (σ_R) and charge changing (σ_cc) cross sections in the Glauber model, as well as the α (cluster)-daughter interaction energy. The latter is then employed to estimate the decay half lives of Super-Heavy (trans-actinide) nuclei in the WKB approximation. The calculations are found to agree well with the experiment. This success of the RMF in accurately describing the nuclear properties with only a few fixed parameters is indeed remarkable. The text was submitted by the authors in English.     

Quasi-cycles and sensitive dependence on seed values in edge of chaos behaviour in a class of self-evolving maps

In a recent paper [Melby P, Kaidel J, Weber N, Hubler A. Adaptation to the edge of chaos in the self-adjusting logistic map. Phys Rev Lett 2000;84:5991–3], Melby et al. attempted to understand edge of chaos behaviour through a very simple model. Based on our exhaustive numerical experiments, here we show that the model, with the definition of the edge of chaos given in the paper, cannot unequivocally support the idea of adaptation to the edge of chaos, let alone allow a conjecture of its generic presence in systems having the same characteristic features.     

Protein‐Functionalized Synthetic Antiferromagnetic Nanoparticles for Biomolecule Detection and Magnetic Manipulation

Direct protein functionalization provides synthetic antiferromagnetic nanoparticles with high chemical specificity and multifunctionality. These nanoparticle–protein conjugates function as improved magnetic labels for biological detection experiments, and exhibit tunable responses to a small external magnetic field gradient, thus allowing the observation of distinctive single nanoparticle motion.

     

A self-consistent particle spectrum for Brueckner calculations

The energies of low-lying intermediate states used in Brueckner calculations on ¹⁶O are calculated self-consistently. When the spectrum for higher intermediate states is chosen to join smoothly to the self-consistent results, the binding energy per nucleon for ¹⁶O is found to be about 7 MeV.     

RPA in wavefunction representation

The RPA is formulated in subspaces of coordinate-like and momentum-like 1 ph operators. This allows to embed a large class of approximative schemes into a generalized RPA treatment. We give a detailed formulation in terms of wavefunctions in coordinate space which is ideally suited to practical programming. In particular, we work out the reduction to spherical tensors in the case of spherical symmetry which is most often the starting point in finite Fermion systems.     

Effective operators and the truncation of shell model configuration space

An alternative derivation of the projection method for constructing effective operators in the truncated shell model space is presented. The results of explicit numerical calculations in three different nuclear regions are discussed. Non-hermiticity of the effective Hamiltonian and various hermitisation procedures are investigated in detail.     

High spin spectroscopy of 139Pr

The high spin states in N=80 ¹³⁹Pr have been investigated by in-beam γ-spectroscopic techniques following the reaction ¹³⁰Te (¹⁴N, 5n) reaction at E=75 MeV, using a gamma detector array, consisting of seven 23% compton-suppressed high purity germanium detectors and a multiplicity ball of fourteen bismuth germanate elements. Based on γ-γ coincidence data, the level scheme of ¹³⁹Pr has been considerably extended up to 7.2 MeV excitation. Tentative spin-parity assignments are done for the newly proposed levels on the basis of the DCO ratios corresponding to strong gates and the available information from the earlier light ion experiments.