X‐ray absorption measurements on an ultrasonic spray aerosol

Spray deposition of thin films and coatings is a widely used manufacturing process owing to its low cost, versatility and simple implementation. The objective of the presented experiments was to investigate whether X‐ray absorption measurements on solutes carried by aerosols are possible, and what count rates can be achieved depending on solution flow through and the resulting mass density in the interrogation volume. The investigated prototypical spray aerosol was InCl₃ dissolved in water or ethanol dispersed via an ultrasonic nebulizer. InCl₃ spray is essential for the ion layer gas reaction process used for the deposition of In₂S₃ buffer layers for highly efficient chalcopyrite solar cells. The discussed experiments demonstrate that measurements are possible, but that the achievement of good signal‐to‐noise ratios requires extended sampling times and concentrated solutions.     

High transmission 3D printed flex‐PCB‐based ion funnel

In this study a novel fabrication method for a radio frequency (RF) ion funnel is presented. RF ion funnels are important devices for focusing ion clouds at low vacuum conditions for mass spectrometry or deposition‐related applications. Typically, ion funnels are constructed of stainless steel plate ring electrodes with a decreasing diameter where RF and direct current potentials are applied to the electrodes to focus the ion cloud. The presented novel design is based on a flexible circuit board that serves both as the signal distribution circuit and as the electrodes of the ion funnel. The flexible circuit board is rolled into a 3D printed scaffold to create a funnel shape with ring electrodes formed by the copper electrodes of the flexible circuit board. The design is characterized in direct comparison with a conventional steel‐plate electrode design. The discussed results show that the new funnel has similar performance to the conventionally designed funnel despite much lower manufacturing costs. Copyright © 2015 John Wiley & Sons, Ltd.     

Palladium(II)-catalyzed transfer vinylation of protected monosaccharides

A method for the catalytic vinylation of protected monosaccharides bearing a single free hydroxyl function has been developed. Reaction of representative primary, secondary, and anomeric sugar hydroxyl functions with butyl vinyl ether as the reactant and solvent and (phen)Pd(OAc)(2) (phen = 1,10-phenanthroline ligand) as the catalyst gives the corresponding vinylated sugar products in 36-79% yield. The catalyst requires the presence of traces of oxygen in the reaction mixture to prevent decomposition to Pd(0).     

Regioselectively trisilylated hexopyranosides through homogeneously catalyzed silane alcoholysis

The iridium complex [Ir(COD)(PPh3)2]+ SbF6- reacts with tert-butyldimethylsilane in DMA to form [IrH2(Sol)2(PPh3)2]+ SbF6-, which is an active catalyst for the regioselective di- and trisilylation of a series of representative methyl hexopyranosides, beta-1,6-anhydrohexopyranosides and 1,3,5-O-methylidene inositol. The corresponding 2,3,6- and 2,4,6-silylated glycosides are obtained in a separable mixture of 47-89% (2,3,6-isomers) and 9-25% (2,4,6-isomers) yield in a single-pot reaction. The 2,4-disilylated derivatives of mannosan, galactosan, and 1,3,5-O-methylidene inositol as well as persilylated levoglucosan are accessible in >85% yield by this method. The homogeneous nature of the catalysts is a prerequisite for the effective di-/trisilylation, as nanoparticle colloid catalysts generated in situ from Pd2(dba)3 (approximately 1.5 nm average particle size) or Ru2Cl5(MeCN)7 (approximately 0.65 nm average particle size) result in only low yields.     

Uncountable Cofinalities of Permutation Groups

A sufficient criterion is found for certain permutation groupsG to have uncountable strong cofinality, that is, they cannotbe expressed as the union of a countable, ascending chain (H_i)_i     

All Groups are Outer Automorphism Groups of Simple Groups

It is shown that each group is the outer automorphism groupof a simple group. Surprisingly, the proof is mainly based onthe theory of ordered or relational structures and their symmetrygroups. By a recent result of Droste and Shelah, any group isthe outer automorphism group Out (Aut T) of the automorphismgroup Aut T of a doubly homogeneous chain (T, ). However, AutT is never simple. Following recent investigations on automorphismgroups of circles, it is possible to turn (T, ) into a circleC such that Out (Aut T) Out (Aut C). The unavoidable normalsubgroups in Aut T evaporate in Aut C, which is now simple,and the result follows.     

Engineering de novo membrane-mediated protein-protein communication networks

Mechanical properties of biological membranes are known to regulate membrane protein function. Despite this, current models of protein communication typically feature only direct protein-protein or protein-small molecule interactions. Here we show for the first time that, by harnessing nanoscale mechanical energy within biological membranes, it is possible to promote controlled communication between proteins. By coupling lipid-protein modules and matching their response to the mechanical properties of the membrane, we have shown that the action of phospholipase A(2) on acyl-based phospholipids triggers the opening of the mechanosensitive channel, MscL, by generating membrane asymmetry. Our findings confirm that the global physical properties of biological membranes can act as information pathways between proteins, a novel mechanism of membrane-mediated protein-protein communication that has important implications for (i) the underlying structure of signaling pathways, (ii) our understanding of in vivo communication networks, and (iii) the generation of building blocks for artificial protein networks.     

Comparison of ribonucleic acid homopolymer ionization energies and charge injection barriers

Thin films of guanosine and uridine ribonucleic acid (RNA) homopolymers (poly rG, poly rU) were grown in high vacuum in several steps on highly oriented pyrolytic graphite (HOPG) using electrospray deposition. Between deposition steps, the sample surface was characterized with X-ray and ultraviolet photoemission spectroscopy (XPS, UPS). The resulting spectra series allowed the determination of the orbital alignment at the HOPG interface, as well as the ionization energies of the homopolymer thin films. Comparison with earlier results on cytidine and adenosine RNA homopolymers (poly rC, poly rA) indicates significant ionization energy and charge injection barrier differences between purines and pyrimidines.