Novel Copolymers of Styrene. 17. Ring-Trisubstituted Methyl 2-Cyano-3-Phenyl-2-Propenoates

Electrophilic trisubstituted ethylenes, ring-trisubstituted methyl 2-cyano-3-phenyl-2-propenoates, RPhCH = C(CN)CO₂CH₃ (where R is 2,4,6-trimethyl, 3,5-dimethoxy-4-hydroxy, 3,5-dimethyl-4-hydoxy, 3,4,5-trimethoxy, 2-bromo-3-hydroxy-4-methoxy, 5-bromo-2,3-dimethoxy, 5-bromo-2,4-dimethoxy, 6-bromo-3,4-dimethoxy were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-trisubstituted benzaldehydes and methyl cyanoacetate, and characterized by CHN analysis, IR, ¹H and ¹³C-NMR. All the ethylenes were copolymerized with styrene (M₁) in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, ¹H and ¹³C-NMR. The order of relative reactivity (1/r₁) for the monomers is 5-bromo-2,3-dimethoxy (2.69) > 3,4,5-trimethoxy (1.86) > 6-bromo-3,4-dimethoxy (0.84) > 5-bromo-2,4-dimethoxy (0.39) > 4-hydoxy-3,5-dimethyl (0.31) = 2-bromo-3-hydroxy-4-methoxy (0.31) > 3,5-dimethoxy-4-hydroxy (0.24) > 2,4,6-trimethyl (0.22). Relatively high T_g of the copolymers in comparison with that of polystyrene indicates a decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500ºC range with residue (1–6% wt), which then decomposed in the 500–800ºC range.     

Composition operators acting on Besov spaces on the real line

We study the composition operator \(T_f(g):= f\circ g\) on Besov spaces \(B_{{p},{q}}^{s}(\mathbb{R })\) . In case \(1 < p< +\infty ,\, 0< q \le +\infty \) and \(s>1+ (1/p)\) , we will prove that the operator \(T_f\) maps \(B_{{p},{q}}^{s}(\mathbb{R })\) to itself if, and only if, \(f(0)=0\) and \(f\) belongs locally to \(B_{{p},{q}}^{s}(\mathbb{R })\) . For the case \(p=q\) , i.e., in case of Slobodeckij spaces, we can extend our results from the real line to \(\mathbb{R }^n\) .     

CO(III)–NI(II) double substituted bismuth vanadate: synthesis,phase stabilization,and structural and electrical characterization

Samples of Co–Ni double substituted bismuth vanadate, BICO_0.20?x NI _x VOX (Bi₄Co_0.20???x ^(III)Ni _x ^(II)V_1.8O_{10.8???(x/2)???δ} ;0?≤?x?≤?0.20) were synthesized by standard solid state reactions. The influence of Ni substitution for Co on phase stabilization and oxide-ion performance have been investigated using X-ray powder diffraction, differential thermal analysis, and AC impedance spectroscopy. The high conducting γ′-phase was effectively stabilized at room temperature for compositions with x?≥?0.13 whose thermal stability increases with Ni content. The complex plane plots of impedance were typically represented at temperatures below 380 °C, suggesting a major contribution of polycrystalline grains to the overall electrical conductivity. The dielectric permittivity measurements revealed the fact that suppression of the ferroelectric transition is compositionally dependent. Interestingly, the maximum ionic conductivity at lower temperatures (～2.56?×?10^?4 S cm^?1 at 300 °C) was observed for the composition with x?=?0.13. However, a good agreement was generally found between the values of electrical conductivity and corresponding activation energies of conduction.     

Le problème de Yamabe avec singularités

Let (Mn,g) be a compact riemannian manifold of dimension n?3. Under some assumptions, we prove that there exists a positive function φ solution of the Yamabe equation

     

SMM-chemokines: a class of unnatural synthetic molecules as chemical probes of chemokine receptor biology and leads for therapeutic development

Chemokines and their receptors play important roles in numerous physiological and pathological processes. To develop natural chemokines into receptor probes and inhibitors of pathological processes, the lack of chemokine-receptor selectivity must be overcome. Here, we apply chemical synthesis and the concept of modular modifications to generate unnatural synthetically and modularly modified (SMM)-chemokines that have high receptor selectivity and affinity, and reduced toxicity. A proof of the concept was shown by transforming the nonselective viral macrophage inflammatory protein-II into new analogs with enhanced selectivity and potency for CXCR4 or CCR5, two principal coreceptors for human immunodeficiency virus (HIV)-1 entry. These new analogs provided insights into receptor binding and signaling mechanisms and acted as potent HIV-1 inhibitors. These results support the concept of SMM-chemokines for studying and controlling the function of other chemokine receptors.