Evidence for Triplet Sensitization in the Visible‐Light‐Induced [2+2] Photocycloaddition of Eniminium Ions

Εniminium ions were prepared from the corresponding α,β‐unsaturated carbonyl compounds (enones and enals), and were found to be promoted to their respective triplet states by energy transfer. The photoexcited intermediates underwent intra‐ or intermolecular [2+2] photocycloaddition in good yields (50–78 %) upon irradiation at λ=433 nm or λ=457 nm. Iridium or ruthenium complexes with a sufficiently high triplet energy were identified as efficient catalysts (2.5 mol % catalyst loading) for the reaction. The intermolecular [2+2] photocycloaddition of an eniminium ion derived from a chiral secondary amine proceeded with high enantioselectivity (88 % ee).     

Sensing Picomolar Concentrations of RNA Using Switchable Plasmonic Chirality

Detecting small sequences of RNA in biological samples such as microRNA or viral RNA demands highly sensitive and specific methods. Here, a reconfigurable DNA origami template has been used where a chiral arrangement of gold nanorods on the structure can lead to the generation of strong circular dichroism (CD). Switching of the cross‐like DNA structure is achieved by the addition of nucleic acid sequences, which arrests the structure in one of the possible chiral states by specific molecular recognition. A specific sequence can thus be detected through the resulting changes in the plasmonic CD spectrum. We show the sensitive and selective detection of a target RNA sequence from the hepatitis C virus genome. The RNA binds to a complementary sequence that is part of the lock mechanism, which leads to the formation of a defined state of the plasmonic system with a distinct optical response. With this approach, we were able to detect this specific RNA sequence at concentrations as low as 100 pm .     

Rough asymptotics for tandem non-homogeneous $$M/G/\infty$$ queues via Poissonized empirical processes

We obtain a large deviations principle and moderate deviations principle for the joint distribution of the queue length processes and departure process for tandem queues. The results are obtained by applying a result providing necessary and sufficient conditions on a class of functions for a large deviations principle and moderate deviations principle to hold for a Poissonized empirical process over the class of functions. As an application, we examine how large queue lengths and numbers of departures are built up. This revised version was published online in June 2006 with corrections to the Cover Date.     

Additivity of quasi-measures

We prove that quasi-measures on compact Hausdorff spaces are countably additive. Contained in this result is a proof that every quasi-measure decomposes uniquely into a measure and a quasi-measure that has no smaller measure beneath it. We also show that it is consistent with the usual axioms of set-theory that quasi-measures on compact Hausdorff spaces are -additive. Finally, we construct an example that places strong restrictions on other forms of additivity.

     

AGANTG: a Microsoft EXCEL 5.0-visual basic routine for the analysis of dose-response data

A Microsoft EXCEL 5.0 program was developed to evaluate data from biochemical and functional bioassays, an important step in drug discovery. The program accommodates both agonist and antagonist data. The program, written entirely in Visual Basic, is compatible with both Macintosh and PC platforms. Data are conveniently entered into a worksheet following only a few simple rules. The program performs complex data analysis and outputs calculated and graphic results to EXCEL worksheets. A set-up routine with a convenient dialog box offers the user controls regarding data analysis and results formats. After determining if the data are from an agonist or antagonist assay, the program automatically performs the analysis and outputs results in the proper format. Calculations support Schild analysis for antagonists. An agonist and antagonist were analyzed to illustrate program usage and results generated by the analysis. EXCEL-Visual Basic is a useful and convenient tool for evaluating bioassay data. Data entry is greatly simplified and custom reports can be generated with relative ease. Data are stored in a format that allows for easy editing re-analysis.     

From Groundwork to Efficient Solar Cells: On the Importance of the Substrate Material in Co-Evaporated Perovskite Solar Cells

Vacuum-based deposition of optoelectronic thin films has a long-standing history. However, in the field of perovskite-based photovoltaics, these techniques are still not as advanced as their solution-based counterparts. Although high-efficiency vacuum-based perovskite solar cells reaching power conversion efficiencies (PCEs) above 20% are reported, the number of studies on the underlying physical and chemical mechanism of the co-evaporation of lead iodide and methylammonium iodide is low. In this study, the impact of one of the most crucial process parameters in vacuum processes—the substrate material—is studied. It is shown that not only the morphology of the co-evaporated perovskite thin films is significantly influenced by the surface polarity of the substrate material, but also the incorporation of the organic compound into the perovskite framework. Based on these studies, a selection guide for suitable substrate materials for efficient co-evaporated perovskite thin films is derived. This selection guide points out that the organic vacuum-processable hole transport material 2,2″,7,7″-tetra(N,N-di-p-tolyl)amino-9,9-spirobifluorene is an ideal candidate for the fabrication of efficient all-evaporated perovskite solar cells, demonstrating PCEs above 19%. Furthermore, building on the insights into the formation of the perovskite thin films on different substrate materials, a basic crystallization model for co-evaporated perovskite thin films is suggested.     

Sparse dimension reduction based on energy and ball statistics

Advances in Data Analysis and Classification - Two new methods for sparse dimension reduction are introduced, based on martingale difference divergence and ball covariance, respectively. These...     

Crystal structure and solid-state31P CP-MAS NMR spectrum of the bis(trifluoroacetato) (triphenylphosphine)mercury(II) dimer [Hg(CF3CO2)2PPh3]2

The title compound belongs to the monoclinic space groupP2₁/c,a=20.29(1),b=12.644(8),c=18.25(1), Å,=95.76(5)°. The unit cell contains two dimeric [Hg(CF₃CO₂)₂PPh₃]₂ molecules in which each Hg atom forms strong primary bonds to a PPh₃ molecule and an oxygen of a monodentate trifluoroacetate ligand. These two Hg atoms are bridged by two extra trifluoroacetate ligands, one providing a single oxygen to a Hg-O-Hg bridge, the other including both carboxylate oxygens in a Hg-O-C-O-Hg bridging moiety. This unusual type of bridging makes the two halves of the molecule symmetry independent, leading to distinct signals at 31.5 and 29.9 ppm for the phosphines in the³¹P CP-MAS NMR spectrum of the solid complex.