Online monitoring of nanoparticle suspensions using dynamic light scattering, ultrasound spectroscopy and process tomography

Dynamic light scattering, ultrasound spectroscopy and electrical resistance tomography were investigated for online monitoring of nanoparticle suspensions. This integrated system provides real time information about particle size distribution, zeta potential and particle concentration and visualises the mixing quality between particles and liquids. As particle size distribution is an indicator of the quality of particulate products, zeta potential measures the stability of colloidal particles and tomography shows particle concentration and the mixing quality between particles and liquids, this integrated multiple sensor system can be applied to nanoparticle manufacturing processes for online process and product quality control

Egr2 overexpression in Schwann cells increases myelination frequency in vitro

Schwann cells are key players in peripheral nerve regeneration, and are uniquely capable of remyelinating axons in this context. Schwann cells orchestrate this process via a set of transcription factors. While it has been shown that overexpression of specific genes, e.g. Egr2, upregulates myelin-related transcripts, it remains unknown if such manipulation can functionalize the cells and enhance their myelination frequency. The ability to do so could have implications in the use of human stem cell-derived Schwann cells, where myelination is hard to achieve. After screening four candidate transcription factors (Sox10, Oct6, Brn2 and Egr2), we found that overexpression of Egr2 in rat Schwann cells co-cultured with sensory neurons enhanced myelination frequency and reduced cell proliferation. However, in a mouse model of sciatic nerve repair with cells engrafted within a nerve guide, myelination frequency in the engrafted cells was reduced upon Egr2 overexpression. Our results show that while overexpression of Egr2 can enhance the myelination frequency in vitro, it is context-dependent, potentially influenced by the microenvironment, timing of association with axons, expression level, species differences, or other factors

Iron Complexes of Square Planar Tetradentate Polypyridyl-Type Ligands as Catalysts for Water Oxidation

The tetradentate ligand, 2-(pyrid-2′-yl)-8-(1″,10″-phenanthrolin-2″-yl)-quinoline (ppq) embodies a quaterpyridine backbone but with the quinoline C8 providing an additional sp² center separating the two bipyridine-like subunits. Thus, the four pyridine rings of ppq present a neutral, square planar host that is well suited to first-row transition metals. When reacted with FeCl₃, a μ-oxo-bridged dimer is formed having a water bound to an axial metal site. A similar metal-binding environment is presented by a bis-phenanthroline amine (dpa) which forms a 1:1 complex with FeCl₃. Both structures are verified by X-ray analysis. While the Fe^III(dpa) complex shows two reversible one-electron oxidation waves, the Fe^III(ppq) complex shows a clear two-electron oxidation associated with the process H₂O–Fe^IIIFe^III → H₂O–Fe^IVFe^IV → OFe^VFe^III. Subsequent disproportionation to an FeO species is suggested. When the Fe^III(ppq) complex is exposed to a large excess of the sacrificial electron-acceptor ceric ammonium nitrate at pH 1, copious amounts of oxygen are evolved immediately with a turnover frequency (TOF) = 7920 h^–1. Under the same conditions the mononuclear Fe^III(dpa) complex also evolves oxygen with TOF = 842 h⁻¹

ARE Update Volume 9, Number 1

Co-editors’ Introduction: Special Issue: China’s Agricultural Boom, with Implications for California.Genetically Modified Rice in China: Effects on Farmers–in China and California.China’s Strawberry Industry: An Emerging Competitor for California?New Horizons for Rural Reform in China: Resources, Property Rights and Consumerism

Light-Driven Proton Reduction in Aqueous Medium Catalyzed by a Family of Cobalt Complexes with Tetradentate Polypyridine-Type Ligands

A series of tetradentate 2,2′:6′,2″:6″,2‴-quaterpyridine-type ligands related to ppq (ppq = 8-(1″,10″-phenanthrol-2″-yl)-2-(pyrid-2′-yl)­quinoline) have been synthesized. One ligand replaces the 1,10-phenanthroline (phen) moiety of ppq with 2,2′-bipyridine and the other two ligands have a 3,3′-polymethylene subunit bridging the quinoline and pyridine. The structural result is that both the planarity and flexibility of the ligand are modified. Co­(II) complexes are prepared and characterized by ultraviolet–visible light (UV-vis) and mass spectroscopy, cyclic voltammetry, and X-ray analysis. The light-driven H₂-evolving activity of these Co complexes was evaluated under homogeneous aqueous conditions using [Ru­(bpy)₃]²⁺ as the photosensitizer, ascorbic acid as a sacrificial electron donor, and a blue light-emitting diode (LED) as the light source. At pH 4.5, all three complexes plus [Co­(ppq)­Cl₂] showed the fastest rate, with the dimethylene-bridged system giving the highest turnover frequency (2125 h^–1). Cyclic voltammograms showed a significant catalytic current for H₂ production in both aqueous buffer and H₂O/DMF medium. Combined experimental and theoretical study suggest a formal Co­(II)-hydride species as a key intermediate that triggers H₂ generation. Spin density analysis shows involvement of the tetradentate ligand in the redox sequence from the initial Co­(II) state to the Co­(II)-hydride intermediate. How the ligand scaffold influences the catalytic activity and stability of catalysts is discussed, in terms of the rigidity and differences in conjugation for this series of ligands