Hydrogen transport through Pd-Ni alloy electrodeposited on Pd substrate

Hydrogen transport through a Pd-Ni alloy electrodeposited on a Pd substrate (Pd-Ni/Pd bilayer symmetric electrode) has been investigated using cyclic voltammetry and a.c. impedance spectroscopy combined with the electrochemical hydrogen permeation method. The permeation build-up current transients and the measured impedance spectra were analyzed using the time-lag method for the bilayer electrode and a complex non-linear least squares data-fitting method based upon the derived Faradaic admittance for the hydrogen absorption into and diffusion through the bilayer electrode under the permeable boundary condition, respectively. The value of the hydrogen diffusivity in the Pd-Ni layer was lower than that in the Pd layer. Furthermore, the values of the charge transfer resistance and equilibrium absorption constant for the Pd-Ni/Pd bilayer electrode were higher than those for the Pd single layer electrode. From the experimental results, the role of the thin Ni(OH)₂ film formed on the Pd-Ni layer surface in the hydrogen transport through the Pd-Ni/Pd bilayer electrode is discussed in terms of its passivating effect and extremely large hydrogen solubility. Received: 22 January 1997 / Accepted: 15 April 1997     

Iron‐catalyzed living radical polymerization of acrylates: Iodide‐based initiating systems and block and random copolymerizations

A half‐metallocene iron iodide complex [Fe(Cp)I(CO)₂] induced living radical polymerization of methyl acrylate (MA) in conjunction with an iodide initiator [(CH₃)₂C(CO₂Et)I, 1 ] and Al(Oi‐Pr)₃ to give polymers of controlled molecular weights and narrow molecular weight distributions (MWDs) (M_w/M_n < 1.2). With the use of chloride and bromide initiators, the MWDs were broader, whereas the molecular weights were similarly controlled. Other acrylates such as n‐butyl acrylate (nBA) and tert‐butyl acrylate (tBA) can be polymerized with 1 /Fe(Cp)I(CO)₂ in the presence of Ti(Oi‐Pr)₄ and Al(Oi‐Pr)₃, respectively, to give living polymers. The 1 /Fe(Cp)I(CO)₂ initiating system is applicable for the synthesis of block and random copolymers of acrylates (MA, nBA, and tBA) and styrene of controlled molecular weights and narrow MWDs (M_w/M_n = 1.2–1.3). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2033–2043, 2002     

Optimization of Solution Condition for an Effective Electrochemical Reduction of N2O

An effective electrochemical reduction of nitrous oxide (N₂O) is established by controlling solution compositions in this study. N₂O was electrochemically reduced varying solvent composition and supporting electrolytes (K₂SO₄ and Na₂SO₄) concentrations. The differences in reduction current density and solution resistance were analyzed via linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS), respectively, depending on solution conditions. UV‐Vis spectroscopy was adopted to measure the solubility of N₂O. As a result, among the conditions investigated in this study, 300 mM of K₂SO₄ and aqueous based solution were revealed as an optimum condition for the electrochemical N₂O reduction. At 300 mM of K₂SO₄, the highest current density was obtained due to a high conductance of the electrolyte and a moderate solubility of N₂O.     

Novel silicon-based alternating copolymers: synthesis,photophysical properties,and tunable EL colors

We synthesized novel silicon-based alternating copolymers for tunable electroluminescent (EL) colors by Heck synthetic method. Their thermal, photophysical and electroluminescent properties were studied. Most of them exhibited a blue-green EL color at the operating voltage of lower than 12 V. Unusually, we observed the white EL color from a EL device based on SiPhPVK. From photophysical studies and the time-resolved PL spectroscopies, it might be attributed to the formation of stabilized excited state in SiPhPVK. Furthermore, in order to reduce the operating voltage of their LED with increasing the electron affinity of the main chain in silicon-based alternating copolymers, we synthesized the silicon-based copolymers containing electron transporting oxadiazole units in main chain. We also studied their photophysical and electroluminescent properties.     

Structure of the stapled p53 peptide bound to Mdm2

Mdm2 is a major negative regulator of the tumor suppressor p53 protein, a protein that plays a crucial role in maintaining genome integrity. Inactivation of p53 is the most prevalent defect in human cancers. Inhibitors of the Mdm2-p53 interaction that restore the functional p53 constitute potential nongenotoxic anticancer agents with a novel mode of action. We present here a 2.0 ? resolution structure of the Mdm2 protein with a bound stapled p53 peptide. Such peptides, which are conformationally and proteolytically stabilized with all-hydrocarbon staples, are an emerging class of biologics that are capable of disrupting protein-protein interactions and thus have broad therapeutic potential. The structure represents the first crystal structure of an i, i + 7 stapled peptide bound to its target and reveals that rather than acting solely as a passive conformational brace, a staple can intimately interact with the surface of a protein and augment the binding interface.     

Effect of plasma etching on photoluminescence of SnO(x)/Sn nanoparticles deposited on DOPC lipid membrane

The photoluminescence characteristic of the SnO(x)/Sn nanoparticles deposited on a solid supported liquid-crystalline phospholipid (1,2-dioleoyl-sn-glycero-3-phosphocholine) membrane was probed after plasma etching the nanoparticle monolayer. It was shown that the plasma etching of the nanoparticle surface greatly altered the particle morphology and enhanced the PL effect, especially when the particle size was below 10 nm in spite of strong presence of surrounding carbon. The enhancement mainly stemmed from the growth of a new PL peak due to the additional defect states produced on the nanoparticle surface by the plasma etching. It was also shown that hydrating the SnO(x)/Sn nanoparticles similarly improved the PL response of the nanoparticles as the hydration produced an additional oxygen-rich oxide layer on the particle surface.     

Aurones and Flavonols from Coreopsis lanceolata L. Flowers and Their Anti-Oxidant,Pro-Inflammatory Inhibition Effects,and Recovery Effects on Alloxan-Induced Pancreatic Islets in Zebrafish

(1) Background: Many flavonoids have been reported to exhibit pharmacological activity; a preparatory study confirmed that Coreopsis lanceolata flowers (CLFs) contained high flavonoid structure content; (2) Methods: CLFs were extracted in aqueous methanol (MeOH:H₂O = 4:1) and fractionated into acetic ester (EtOAc), normal butanol (n-BuOH), and H₂O fractions. Repeated column chromatographies for two fractions led to the isolation of two aurones and two flavonols; (3) Results: Four flavonoids were identified based on a variety of spectroscopic data analyses to be leptosidin (1), leptosin (2), isoquercetin (3), and astragalin (4), respectively. This is the first report for isolation of 2–4 from CLFs. High-performance liquid chromatography (HPLC) analysis determined the content levels of compounds 1–4 in the MeOH extract to be 2.8 ± 0.3 mg/g (1), 17.9 ± 0.9 mg/g (2), 3.0 ± 0.2 mg/g (3), and 10.9 ± 0.9 mg/g (4), respectively. All isolated compounds showed radical scavenging activities and recovery activities in Caco-2, RAW264.7, PC-12, and HepG2 cells against reactive oxygen species. MeOH extract, EtOAc fraction, and 1–3 suppressed NO formation in LPS-stimulated RAW 264.7 cells and decreased iNOS and COX-2 expression. Furthermore, all compounds recovered the pancreatic islets damaged by alloxan treatment in zebrafish; (4) Conclusions: The outcome proposes 1–4 to serve as components of CLFs in standardizing anti-oxidant, pro-inflammatory inhibition, and potential anti-diabetic agents.