Controllability of stochastic Volterra integrodifferential systems

In this paper, sufficient conditions for the controllability of stochastic integrodifferential systems in Banach spaces are established. The results are obtained by using a fixed point theorem. An example is provided to illustrate the theory.     

The alkaloids of the mersinine group: a new subclass of the monoterpenoid indole alkaloids from Kopsia

A total of 16 alkaloids, exemplified by mersinine A and its congeners, and constituting a new subclass of the monoterpenoid indoles, were isolated exclusively and for the first time from Kopsia singapurensis. The structures of these alkaloids were established by spectroscopic methods and in some instances confirmed by X-ray diffraction analysis. A possible biogenetic route from an aspidofractinine precursor is proposed. Compounds 1, 2, 3, 9, and 10 were found to reverse multidrug-resistance in drug-resistant KB cells.     

Reconstitution of rhodopsin into polymerizable planar supported lipid bilayers: influence of dienoyl monomer structure on photoactivation

G-protein-coupled receptors (GPCRs) play key roles in cellular signal transduction and many are pharmacologically important targets for drug discovery. GPCRs can be reconstituted in planar supported lipid bilayers (PSLBs) with retention of activity, which has led to development of GPCR-based biosensors and biochips. However, PSLBs composed of natural lipids lack the high stability desired for many technological applications. One strategy is to use synthetic lipid monomers that can be polymerized to form robust bilayers. A key question is how lipid polymerization affects GPCR structure and activity. Here we have investigated the photochemical activity of bovine rhodopsin (Rho), a model GPCR, reconstituted into PSLBs composed of lipids having one or two polymerizable dienoyl moieties located in different regions of the acyl chains. Plasmon waveguide resonance spectroscopy was used to compare the degree of Rho photoactivation in fluid and poly(lipid) PSLBs. The position of the dienoyl moiety was found to have a significant effect: polymerization near the glycerol backbone significantly attenuates Rho activity whereas polymerization near the acyl chain termini does not. Differences in cross-link density near the acyl chain termini also do not affect Rho activity. In unpolymerized PSLBs, an equimolar mixture of phosphatidylethanolamine and phosphatidylcholine (PC) lipids enhances activity relative to pure PC; however after polymerization, the enhancement is eliminated which is attributed to stabilization of the membrane lamellar phase. These results should provide guidance for the design of robust lipid bilayers functionalized with transmembrane proteins for use in membrane-based biochips and biosensors.     

The effect of double-chain surfactants on armored bubbles: a surfactant-controlled route to colloidosomes

We find that the gas phases of air bubbles covered with anionic or cationic polystyrene latex particles dissolve on exposure to cationic and catanionic surfactants. The particles on the bubble interface are released as singlets or aggregates when the surfactant has a single hydrophobic chain, while porous colloidal capsules (colloidosomes) with the same aqueous phase inside as out are obtained when the surfactant has two hydrophobic chains. The formation of colloidosomes from the particle-covered bubbles does not appear to depend significantly on the charge of the particles, which makes it unlikely that bilayers of surfactant are stabilizing the colloidosome. While the exact mechanism of formation remains an open question, our method is a simple one-step process for obtaining colloidosomes from particle-covered bubbles.     

Quantitative treatment of the ortho-effect in reactions of ortho-substituted phenylmercaptoacetic acids

The kinetics of oxidation of ortho-substituted phenylmercaptoacetic acids by bromamine T and metaperiodate ion and also thepk _a values of these acids have been studied. Regression analyses of the rate and equilibrium data indicate that the ortho-substituent effect can be explained by the electrical effects alone, and that in these acids when the reaction site is in close proximity to the ortho-substituent or not, the steric effect is insignificant. The rates of oxidation and the ionization constants of these acids are largely controlled by the inductive effect.     

Synthesis and structural characterization of high spin M/Cu (M = Mn, Fe) heterobimetallic and Fe/Cu2 trimetallic phosphinoamides

The heterobimetallic complexes [Mn((i)PrNPPh(2))(3)Cu((i)PrNHPPh(2))] (1) and [Fe((i)PrNPPh(2))(3)Cu((i)PrNHPPh(2))] (2) have been synthesized by the one pot reaction of LiN(i)PrPPh(2), MCl(2) (M = Mn, Fe), and CuI in high yield. Addition of excess CuI into 2 or directly to the reaction mixture led to the formation of a heterotrimetallic [Fe((i)PrNPPh(2))(3)Cu(2)((i)PrNPPh(2))] (3) in good yield. Complexes 1-3 have been characterized by means of elemental analysis, paramagnetic (1)H NMR, UV-vis spectroscopy, cyclic voltammetry, and single crystal X-ray analysis. In all three complexes, Mn or Fe are in the +2 oxidation state and have a high spin electron configuration, as evidenced by solution Evans' method. In addition, the oxidation state of Fe in complex 3 is confirmed by zero-field (57)Fe M?ssbauer spectroscopy. X-ray crystallography reveals that the three coordinate Mn/Fe centers in the zwitterionic complexes 1-3 adopt an unusual trigonal planar geometry.     

Synthesis of first ever 4-quinolone-3-carboxylic acid-appended spirooxindole-pyrrolidine derivatives and their biological applications

A series of 4-quinolone-3-carboxylic acid-containing spirooxindole-pyrrolidine derivatives was synthesized via multicomponent 1,3-dipolar cycloaddition reactions of azomethine ylides with new (E)-4-oxo-6-(3-phenyl-acryloyl)-1,4-dihydroquinoline-3-carboxylic acids in good yields with high regioselectivity. The cycloadducts were characterized by analytical and spectral data including \(^{1}\hbox {H}\), \(^{13}\hbox {C}\), 2D NMR and mass spectroscopy. The structure of one of the compounds (8a) was investigated theoretically by computational techniques. DFT studies support the proposed mechanism for this cycloaddition reaction. Furthermore, antibacterial activities of the new compounds were evaluated against Gram-positive and Gram-negative bacterial strains. Compounds 8f, 8m and 8p showed potent inhibition activities against selected bacteria. The in vitro cytotoxicity of spirooxindole derivatives (8a–r) was evaluated against MCF-7 breast cancer cell line. Among the various compounds tested, compound 8f \((\hbox {IC}_{50} = 18.35~\upmu \hbox {M})\) showed significant cytotoxic activity compared to the standard drug doxorubicin \((\hbox {IC}_{50 }= 15.00~\upmu \hbox {M})\).     

Effect of Particle Clusters on Carrier Flow Turbulence: A Direct Numerical Simulation Study

Experiments indicate that particle clusters that form in fluidized–bed risers can enhance gas-phase velocity fluctuations. Direct numerical simulations (DNS) of turbulent flow past uniform and clustered configurations of fixed particle assemblies at the same solid volume fraction are performed to gain insight into particle clustering effects on gas-phase turbulence, and to guide model development. The DNS approach is based on a discrete-time, direct-forcing immersed boundary method (IBM) that imposes no-slip and no-penetration boundary conditions on each particle’s surface. Results are reported for mean flow Reynolds number Re _p ?=?50 and the ratio of the particle diameter d _p to Kolmogorov scale is 5.5. The DNS confirm experimental observations that the clustered configurations enhance the level of fluid-phase turbulent kinetic energy (TKE) more than the uniform configurations, and this increase is found to arise from a lower dissipation rate in the clustered particle configuration. The simulations also reveal that the particle-fluid interaction results in significantly anisotropic fluid-phase turbulence, the source of which is traced to the anisotropic nature of the interphase TKE transfer and dissipation tensors. This study indicates that when particles are larger than the Kolmogorov scale (d _p ?>?η), modeling the fluid-phase TKE alone may not be adequate to capture the underlying physics in multiphase turbulence because the Reynolds stress is anisotropic. It also shows that multiphase turbulence models should consider the effect of particle clustering in the dissipation model.