First examples of pyran based colorants as sensitizing agents of p-Type Dye-Sensitized solar cells

Three different pyran based dyes were synthesized and tested for the first time as photosensitizers of NiO based p-type dye-sensitized solar cells (p-DSSC). The molecules feature a similar molecular structure and are based on a pyran core that is functionalized with electron acceptor groups of different strength and is symmetrically coupled to phenothiazine donor branches. Optical properties of the dyes are deeply influenced by the nature of the electron-acceptor group, so that the overall absorption of the three dyes covers the most of the visible spectrum. The properties of devices based on the NiO electrodes sensitized with the investigated dyes were evaluated under simulated solar radiation: the larger short circuit current density exceeded 1mA/cm2 and power conversion efficiency as high as 0.04% could be recorded. The performances of the fabricated p-DSSC have been compared to a reference cell sensitized with P1, a high level benchmark, which afforded a photoelectrochemical activity similar to the best example of our pyran sensitized devices (1.19 mA/cm2 and 0.049%)

The Binet-Legendre Metric in Finsler Geometry

For every Finsler metric $F$ we associate a Riemannian metric $g_F$ (called the Binet-Legendre metric). The transformation $F \mapsto g_F$ is $C^0$-stable and has good smoothness properties, in contrast to previous constructions. The Riemannian metric $g_F$ also behaves nicely under conformal or bilipshitz deformation of the Finsler metric $F$. These properties makes it a powerful tool in Finsler geometry and we illustrate that by solving a number of named Finslerian geometric problems. We also generalize and give new and shorter proofs of a number of known results. In particular we answer a question of M. Matsumoto about local conformal mapping between two Minkowski spaces, we describe all possible conformal self maps and all self similarities on a Finsler manifold. We also classify all compact conformally flat Finsler manifolds, solve a conjecture of S. Deng and Z. Hou on the Berwaldian character of locally symmetric Finsler spaces, and extend the classic result of H.C. Wang about the maximal dimension of the isometry groups of Finsler manifolds to manifolds of all dimensions. Most proofs in this paper go along the following scheme: using the correspondence $F \mapsto g_F$we reduce the Finslerian problem to a similar problem for the Binet-Legendre metric, which is easier and is already solved in most cases we consider. The solution of the Riemannian problem provides us with the additional information that helps to solve the initial Finslerian problem. Our methods apply even in the absence of the strong convexity assumption usually assumed in Finsler geometry. The smoothness hypothesis can also be replaced by that of partial smoothness, a notion we introduce in the paper. Our results apply therefore to a vast class of Finsler metrics not usually considered in the Finsler literature.Comment: 33 pages, 5 figures. This version is slightly reduced fron versions 1 and 2. The paper has been published in Geometry & Topolog

A natural Finsler--Laplace operator

We give a new definition of a Laplace operator for Finsler metric as an average with regard to an angle measure of the second directional derivatives. This definition uses a dynamical approach due to Foulon that does not require the use of connections nor local coordinates. We show using 1-parameter families of Katok--Ziller metrics that this Finsler--Laplace operator admits explicit representations and computations of spectral data.Comment: 25 pages, v2: minor modifications, changed the introductio

Stabilization of an elusive tautomer by metal coordination

The solid-state isolation of the different tautomers of a chemical com­pound can be a challenging problem. In many cases, tautomers with an energy very close to the most stable one cannot be isolated (elusive tautomers). In this article, with reference to the 4-methyl-7-(pyrazin-2-yl)-2H-[1,2,4]triazolo[3,2-c][1,2,4]triazole ligand, for which the elusive 3H-tautomer has an energy only 1.4 kcal mol(−1) greater than the most stable 2H form, we show that metal com­plexation is a suc­cessful and reliable way for stabilizing the elusive tauto­mer. We have pre­pared two com­plexes of the neutral ligand with CuBr(2) and ZnBr(2), namely, aqua­bromido­bis­[4-methyl-7-(pyrazin-2-yl)-3H-[1,2,4]triazolo[3,2-c][1,2,4]triazole]copper(II) bromide trihydrate, [CuBr(C(8)H(7)N(7))(2)(H(2)O)]Br·3H(2)O, and di­bro­mido­[4-methyl-7-(pyrazin-2-yl)-2H-[1,2,4]triazolo[3,2-c][1,2,4]triazole][4-methyl-7-(pyrazin-2-yl)-3H-[1,2,4]triazolo[3,2-c][1,2,4]tri­azole]zinc(II) monohydrate, [ZnBr(2)(C(8)H(7)N(7))(2)]·H(2)O. The X-ray analysis shows that, in both cases, the elusive 3H-tautomer is present. The results of the crystallographic analysis of the two com­plexes reflect the different coordination preferences of Cu(II) and Zn(II). The copper(II) com­plex is homotautomeric as it only con­tains the elusive 3H-tautomer of the ligand. The com­plex can be described as octa­hedral with tetra­gonal distortion. Two 3H-triazolotriazole ligands are bis-chelated in the equatorial plane, while a water mol­ecule and a bromide ion in elongated axial positions com­plete the coordination environment. The zinc(II) com­plex, on the other hand, is heterotautomeric and con­tains two bromide ions and two monodentate ligand mol­ecules, one in the 2H-tautomeric form and the other in the 3H-tautomeric form, both coordinated to the metal in tetra­hedral geometry. The observation of mixed-tautomer com­plexes is unprecedented for neutral ligands. The analysis of the X-ray mol­ecular structures of the two com­plexes allows the deduction of possible rules for a rational design of mixed-tautomer com­plexes

The conserved C-terminus of the PcrA/UvrD helicase interacts directly with RNA polymerase

Copyright: © 2013 Gwynn et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by a Wellcome Trust project grant to MD (Reference: 077368), an ERC starting grant to MD (Acronym: SM-DNA-REPAIR) and a BBSRC project grant to PM, NS and MD (Reference: BB/I003142/1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Distance Counseling: Perceived Advantages and Disadvantages among Christian Counselors

Not available

Strong and pH dependent fluorescence in unprecedented anthra[2,3-d]imidazole derivatives

We here report the synthesis and characterization of three new molecules based on an unprecedented anthra [2,3-d]imidazole unit. The new heterocycle was unexpectedly formed while attempting to obtain 2,3-diacetamidoanthracene by reducing the corresponding anthraquinone molecules by sodium borohydride. The same reaction was successfully performed using two further different 2,3-diamidoanthraquinone derivatives, thus confirming its generality. The chemical identity of the novel molecules was also proved by realizing single crystals suitable for XRD diffraction and solving the crystalline structure of one of the prepared systems. All the molecules are strong blue emitters in ethanol, with fluorescence quantum yields around 0.40. Because of the acid-base properties of anthraimidazole ring, the optical response was investigated at different pH values. While slight differences were observed in acidic conditions, in the alkaline pH range we observed a dramatic change of the fluorescence spectra in a narrow pH range (from 11 to 13), with the color of the emission turning from blue to green. This feature makes the new class of derivatives here reported very promising as pH sensors working in strongly alkaline conditions