Potentiometric and Voltammetric Study of 6‐Benzylaminopurine and Its Derivatives

The protonation‐deprotonation equilibrium of 6‐benzylaminopurine (6‐BAP) and its derivatives was studied by potentiometry and voltammetry. The effect of Cl‐ or OCH₃‐group in position 2′, 3′ and 4′ of the benzene ring of 6‐BAP on both pK_a values was investigated. To determine the enthalpy and entropy, the temperature dependence of pK_a was employed. It was found that with increasing temperature the pK_a decreased. In comparison with 6‐BAP the chloro‐ or methoxy‐ group resulted in pK_a increase. The first pK_a values were also determined by linear sweep (LSV) and elimination voltammetry with linear scan (EVLS). New approaches were shown not only for the determination of pK_a from voltammetric titration curves but also for the evaluation of the reduction processes of benzylaminopurines.     

The influence of sintering conditions on the phase purity of bulk EuTiO3 and Eu0.5Ba0.5TiO3 ceramics

EuTiO₃ and Eu_0.5Ba_0.5TiO₃ ceramics were synthesized using mechanochemical activation of oxide precursors and then calcined. The uniaxially as well as isostatically pressed samples were sintered in different kinds of reducing atmospheres, namely Ar?+?(7–10)%H₂, respectively, 99.99%H₂ in the case of pressureless sintering or in vacuum (enriched by CO vapors) in the case of pressure-assisted spark plasma sintering (SPS). The samples prepared by SPS contained the pyrochlore phase as the second phase. In contrast with SPS, pressureless sintered samples were phase pure, although thermodynamics calculations showed that CO atmosphere in SPS is more reducing than pure hydrogen. This is explained by short sintering times in SPS that do not allow establishment of the thermodynamic equilibrium. The proper choice of sintering temperature, time, and atmosphere enabled preparation of dense and phase pure samples of Eu _x Ba_{1? x} TiO₃ ceramics suitable for the evaluation of “true” physical properties (e.g., infrared reflectivity), or for experimental confirmation of specific functionalities proposed from theory.     

The harmonic moment tail index estimator: asymptotic distribution and robustness

Asymptotic properties of the harmonic moment tail index Estimator are derived for distributions with regularly varying tails. The estimator shows good robustness properties and stands out for its simplicity. A tuning parameter allows for regulating the trade-off between robustness and efficiency. Small sample properties are illustrated by a simulation study.     

Tuning of PEDOT:PSS Properties Through Covalent Surface Modification

Conductive polymer (poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS) is an attractive platform for the design of flexible electronic, optoelectronic, and (bio)sensor devices. Practical application of PEDOT:PSS often requires an incorporation of specific molecules or moieties for tailoring of its physical–chemical properties. In this article, a method for covalent modification of PEDOT:PSS using arenediazonium tosylates was proposed. The procedure includes two steps: chemisorption of diazo‐cations on the PEDOT:PSS surface followed by thermal decomposition of the diazonium salt and the covalent bond formation. Structural and surface properties of the samples were evaluated by XPS, SEM‐EDX, AFM, goniometry, and a range of electric and optical measurements. The developed modification procedure enables tuning of the PEDOT:PSS surface properties such as conductivity and optical absorption. The possibility to introduce various organic functional groups (from hydrophilic to hydrophobic) and to create new groups for further functionalization makes the developed procedure multipurpose. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 378–387     

On the nature of unrestricted orbitals in variational active space wave functions

Active space coupled cluster methods exhibit unusual, nonsmooth spin symmetry-breaking behavior where the unrestricted minimum lies higher in energy at short bond distances and crosses below the restricted solution at longer distances. The restricted solution is also observed to be a stable minimum slightly beyond the symmetry-breaking point. This behavior arises due to differences in the optimal active spaces defining the restricted and unrestricted wave functions and results in unrestricted wave functions that are not strictly size consistent. We suggest a new, size-consistent model that allows the orbitals to break spin symmetry only within the active space.