Radical polymerization of radical-labeled monomers: The triarylmethyl-based radical monomer as an example

Recent development of spin-labeled nitroxide-mediated polymerization (NMP) involving successful polymer preparation with high livingness and narrow dispersity in the presence of persistent trityl-based stable radicals attached to the initiators (90% recovery of a trityl radical signal after the polymerization) led us to the preparation of stable organic radical polymers based on trityl radical-substituted monomers using NMP as the method of polymerization despite the claims in the literature about its expected failure. Here, we present successful radical polymerization and NMP of a trityl radical-based tri- and mono-monomer yielding more than 90% recovery of the trityl radical signal. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2656–2664     

Quadrupole Mass Filter: Design and Performance for Operation in Stability Zone 3

The predicted performance of a quadrupole mass filter (QMF) operating in Mathieu stability zone 3 is described in detail using computer simulations. The investigation considers the factors that limit the ultimate maximum resolution (R_max) and percentage transmission (%Tx), which can be obtained for a given QMF for a particular scan line of operation. The performance curve (i.e., the resolution (R) versus number (N) of radio frequency (rf) cycles experienced by the ions in the mass filter) has been modeled for the upper and lower tip of stability zone 3. The saturation behavior of the performance curve observed in practice for zone 3 is explained. Furthermore, new design equations are presented by examining the intersection of the scan line with stability zone 3. Resolution versus transmission characteristics of stability zones 1 and 3 are compared and the dependence of performance for zones 1 and 3 is related to particular instrument operating parameters.

On the full and block-decoupling of nonlinear functions

We review a method that decouples multivariate functions into linear combinations of a set of univariate (or simpler multivariate) functions of transformed variables. In this way the given nonlinear multiple-input-multiple-output function is decoupled into a structure having simpler parallel internal branches that are linked by linear transformations to the original inputs and outputs. The procedure collects first-order information by evaluating the Jacobian matrix of the given function in a set of points. These matrices are stacked into a three-way tensor, whose decomposition reveals the decoupled representation. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Photoconductivity of poly-<Emphasis Type="Italic">p</Emphasis>-xylylene + CdS nanocomposite films over a wide temperature range

For poly-p-xylylene + CdS (PPX + CdS) nanocomposite films, the dependences of the photo-conductivity σ _ph (T) on the concentration C of CdS nanoparticles, intensity and wavelength of exciting light, and temperature T within 15–300 K are examined. An appreciable photocurrent appears at C ≥ 10 vol %, when a large percolation cluster of CdS nanoparticles is formed. The photocurrent spectrum is compared to the absorption spectrum of the film. The photocurrent I _ph (P) increases with the intensity of light flux P in a wavelength range near 435 nm according to the I _ph (P) ∼ P ⁿ power law, where n < 1. At 15 K, the photoconductivity of films with C ≈ 11.5 and 13.5 vol % is higher than that of a pure CdS film (C = 100 vol %) by factors of ≈100 and ≈30, respectively. For films with C > 11.5 vol %, the σ _ph (T) dependence at low T exhibits a metal-like character (σ _ph (T) decreases with increasing temperature). Atomic force microscopy is used to examine the surface topography of PPX + CdS films, which is found to be strongly dependent on the concentration of nanoparticles. The dark conductivity and photoconductivity of nanocomposite films arise due to the thermo- and photoexcitation transfer of electrons from the CdS nanoparticles to the PPX matrix with the formation of an electronic double layer at the PPX matrix-large percolation CdS cluster interface, a process that populates the phenyl rings of the adjacent PPX layer with excess electrons. As a result, various mechanisms of electron transfer in the polymer matrix can be realized: Mott’s hopping conduction mechanism with variable-range hopping in the matrix between CdS clusters and the metal-like behavior of the conductivity in the polymer shell of the large cluster at low temperatures. The polymer shell contains excess electrons on the phenyl rings -C₆H₄- in the composition of anion-resonances -C₆H₄⁻-.     

Loaded complex equations in the jet collision problem

The evolution of small perturbations developing on the free surface of the flow in a 270° corner is studied. Linear equations of motion are derived, which are solved numerically. The flow is shown to be stable in Eulerian coordinates and unstable in Lagrangian coordinates.     

Influence of surface roughness on the reflective properties of snow

In this paper the influence of 3D effect on snow reflection function (SRF) and albedo is studied in the framework of the stochastic radiative transfer theory. In particular, the corresponding equations for the averaged intensity of reflected light are solved for the ensemble of realizations of the stochastic field κ(r), describing the distribution of 3D elements on the flat semi-infinite snow layer (SISL). The reflection from the underlying SISL is modeled using the solution of the 1D radiative transfer equation. The corresponding look-up tables were compiled beforehand and used in the simulation process. In accordance with the previous studies, it was found that the albedo of snow layer is reduced (in particular, in the infrared region), if 3D effects are taken into account. There is no such a reduction, if light absorption in snow is absent. The 3D effects may increase or decrease SRF depending on the sastrugi fraction and illumination/observation conditions.     

Complex formation of MnII with tetra(p-tert-butyl)thiacalix[4]arene acid in aqueous solutions of surfactants and polymers

The formation of manganese(II) complexes with different stereoisomers of tetraacid based on p-tert-butylthiacalix[4]arene in water, in micellar solutions of nonionogenic surfactants, and in polymer solutions was studied. The formation of complexes with different degrees of ligand protonation was revealed by pH-metric titration and nuclear magnetic relaxation. On the basis of experimental data, the composition and stability constants of the solubilized complexes of stereoisomers of thiacalixarene acid with manganese(II) ions were determined using mathematical simulation methods. The manganese thiacalixarene complexes are unstable in solutions, especially upon the addition of calcium cations and in the presence of nitrilotriacetic acid.     

Structure and Properties of Heterometallics Based on Lanthanides and Transition Metals with Methoxy-β-Diketonates

The possibility of obtaining volatile polynuclear heterometallic complexes containing lanthanides and transition metals bound by methoxy-β-diketonates was studied. New compounds were prepared by cocrystallization of monometallic complexes from organic solvents. Ln(tmhd)₃ were used as initial monometallic complexes (Ln = La, Pr, Sm, Gd, Tb, Dy, Lu; tmhd = 2,2,6,6-tetramethylheptane-3,5-dionate) in combination with TML₂ in various ratios (TM = Cu, Co, Ni, Mn; L: L¹ = 1,1,1-trifluoro-5,5-dimethoxypentane-2,4-dionate, L² = 1,1,1-trifluoro-5,5-dimethoxy-hexane-2,4-dionate, L³ = 1,1,1-trifluoro-5-methoxy-5-methylhexane-2,4-dionate). Heterometallic complexes of the composition [(LnL₂tmhd)₂TM(tmhd)₂] were isolated for light lanthanides Ln= La, Pr, Sm, Gd, and L= L¹ or L². By single crystal XRD, it has been established that heterometallic compounds containing La, Pr, Cu, Co, and Ni are isostructural linear coordination polymers of alternating mononuclear transition metal complexes and binuclear heteroleptic lanthanide complexes, connected by donor–acceptor interactions between oxygen atoms of the methoxy groups and transition metal atoms. A comparison of powder XRD patterns has shown that all heterometallic complexes obtained are isostructural. Havier lanthanides Ln = Tb, Dy, Lu did not form heterometallics. Instead, homometallic complexes Ln(L³)₃ were identified for Ln = Dy, Lu as well as for Ln = La. The thermal properties of the complexes were investigated by TG-DTA and vacuum sublimation tests. The heterometallic complexes were found to be not volatile and decomposed under heating to produce inorganic composites of TM oxides and Ln fluorides. In contrast, Ln(L³)₃ is volatile and may be sublimed in a vacuum. Results of magnetic measurements are discussed for several heterometallic and homometallic complexes.     

The Study of Hypoglycemic Activity of 7-Terpenylcoumarins

Natural and synthetic coumarins are often considered privileged scaffolds for obtaining pharmacological agents with hypoglycemic activity. Chemical modification of coumarins often leads to antidiabetic agents with greater efficacy. In the present work, twenty monoterpene-substituted 7-hydroxycoumarins were synthesized. A new approach using the Mitsunobu reaction was shown to be effective for the synthesis of target compounds. All of the synthesized compounds were evaluated in an oral glucose tolerance test, and two of them containing geranyl and (-)-myrtenyl substituents showed in vivo hypoglycemic action. A possible mechanism of action of these compounds may include inhibition of DPP IV, which was proved in an in vitro test.