Adsorption and photocatalysed destruction of cationic and anionic dyes on mesoporous titania films: Reactions at the air-solid interface

Cationic dyes, such as methylene blue (MB), Thionine (TH) and Basic Fuschin (BF), but not anionic dyes, such as Acid Orange 7 (AO7), Acid Blue 9 (AB9) and Acid Fuschin (AF), are readily adsorbed onto mesoporous titania films at high pH (pH 11), i.e. well above the pzc of titania (pH 6.5), due to electrostatic forces of attraction and repulsion, respectively. The same anionic dyes, but not the cationic dyes, are readily adsorbed on the same titania films at low pH (pH 3), i.e. well below titania's pzc. MB appears to adsorb on mesoporous titania films at pH 11 as the trimer (lambda(max) = 570 nm) but, upon drying, although the trimer still dominates, there is an absorption peak at 665 nm, especially notable at low [MB], which may be due to the monomer, but more likely MB J-aggregates. In contrast, the absorption spectrum of AO7 adsorbed onto the mesoporous titania film at low pH is very similar to the dye monomer. For both MB and AO7 the kinetics of adsorption are first order and yield high rate constants (3.71 and 1.481 g(-1) min(-1)), indicative of a strong adsorption process. Indeed, both MB and AO7 stained films retained much of their colour when left overnight in dye-free pH 11 and 3 solutions, respectively, indicating the strong nature of the adsorption. The kinetics of the photocatalytic bleaching of the MB-titania films at high pH are complex and not well-described by the Julson-Ollis kinetic model [A.J. Julson, D.F. Ollis, Appl. Catal. B. 65 (2006) 315]. Instead, there appears to be an initial fast but not simple demethylation step, followed by a zero-order bleaching and further demethylation steps. In contrast, the kinetics of photocatalytic bleaching of the AO7-titania film give a good fit to the Julson-Ollis kinetic model, yielding values for the various fitting parameters not too dissimilar to those reported for AO7 adsorbed on P25 titania powder. (C) 2008 Elsevier B.V. All rights reserved.

A New Stereocontrolled Synthetic Route to (-)-Echinosporin from D-Glucose via Padwa Allenylsulfone [3+2]-Anionic Cycloadditive Elimination

A new formal total synthesis of (-)-echinosporin has been developed based upon the Padwa [3 + 2]-cycloadditive elimination reaction of allenylsulfone 4 with the D-glucose-derived enone 14 which provides cycloadduct 12.

Metasurfaces with interwoven conductor patterns on dielectric substrates

The properties of metasurfaces comprised of interwoven conductor patterns on dielectric substrates have been examined. The significant reduction of the fundamental resonance frequency fr and expanded fractional bandwidths (FBWs) offered by the intertwined spirals and Brigid’s crosses extended beyond a single unit cell has been achieved with the aid of thin dielectric substrates. A qualitative model has been proposed and proved to adequately predict the main properties of entwined spiral arrays on dielectric substrates.

Loading Artificial Magnetic Conductor and Artificial Magnetic Conductor Absorber with Negative Impedance Convertor Elements

The general properties of a frequency selective surface loaded with negative impedance converter (NIC)-based active loads are discussed from a theoretical perspective.The stability problem associated with NIC circuits embedded in artificial magnetic conductor (AMC) and AMC absorber applications is studied using pole-zero analysis. The requirements and constraints for achieving stable operation with enhanced bandwidth using negative capacitance as realized by a floating NIC network are derived. Furthermore, it is shown that it is nearly impossible to simultaneously implement a negative capacitor and a negative inductor to such structures. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2111–2114, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27019

Tailoring ionic liquid catalysts: structure, acidity and catalytic activity of protonic ionic liquids based on anionic clusters, [(HSO4)(H2SO4)x]− (x = 0, 1, or 2)

Aiming at inexpensive Brønsted-acidic ionic liquids, suitable for industrial-scale catalysis, a family of protonic ionic liquids based on nitrogen bases and sulfuric acid has been developed. Variation of the molar ratio of sulfuric acid, χH2SO4, was used to tune acidity. The liquid structure was studied using 1H NMR and IR spectroscopies, revealing the existence of hydrogen-bonded clusters, [(HSO4)(H2SO4)]−, for χH2SO4 > 0.50. Acidity, quantified by Gutmann Acceptor Number (AN), was found to be closely related to the liquid structure. The ionic liquids were employed as acid catalysts in a model reaction; Fischer esterification of acetic acid with 1-butanol. The reaction rate depended on two factors; for χH2SO4 > 0.50, the key parameter was acidity (expressed as AN value), while for χH2SO4 > 0.50 it was the mass transport (solubility of starting materials in the ionic liquid phase). Building on this insight, the ionic liquid catalyst and reaction conditions have been chosen. Conversion values of over 95% were achieved under exceptionally mild conditions, and using an inexpensive ionic liquid, which could be recycled up to eight times without diminution in conversion or selectivity. It has been demonstrated how structural studies can underpin rational design and development of an ionic liquid catalyst, and in turn lead to a both greener and economically viable process.

High-impedance metasurfaces with interwoven conductor patterns

High impedance metasurfaces (HIMSs) formed by interwoven conductor arrays are proposed. Bandwidth comparable with that of the basic square patches is achieved at an order of magnitude smaller unit cells. The presented structures are apt for small mobile terminals and low frequency applications.

Rules and Stereoelectronic Guidelines for the Anionic Nucleophilic Displacement of Furanoside and Furanose O-sulfonates

Rules for predicting anionic S_N2 displacement viability in furanose and furanoside sulfonates are presented

BRCA1--conductor of the breast stem cell orchestra:the role of BRCA1 in mammary gland development and identification of cell of origin of BRCA1 mutant breast cancer

Breast cancer treatment has been increasingly successful over the last 20 years due in large part to targeted therapies directed against different subtypes. However, basal-like breast cancers still represent a considerable challenge to clinicians and scientists alike since the pathogenesis underlying the disease and the target cell for transformation of this subtype is still undetermined. The considerable similarities between basal-like and BRCA1 mutant breast cancers led to the hypothesis that these cancers arise from transformation of a basal cell within the normal breast epithelium through BRCA1 dysfunction. Recently, however, a number of studies have called this hypothesis into question. This review summarises the initial findings which implicated the basal cell as the cell of origin of BRCA1 related basal-like breast cancers, as well as the more recent data which identifies the luminal progenitor cells as the likely target of transformation. We compare a number of key studies in this area and identify the differences that could explain some of the contradictory findings. In addition, we highlight the role of BRCA1 in breast cell differentiation and lineage determination by reviewing recent findings in the field and our own observations suggesting a role for BRCA1 in stem cell regulation through activation of the p63 and Notch pathways. We hope that through an increased understanding of the BRCA1 role in breast differentiation and the identification of the cell(s) of origin we can improve treatment options for both BRCA1 mutant and basal-like breast cancer subgroups.

Electrochemical promotion of a platinum catalyst supported on the high-temperature proton conductor La0.99Sr0.01NbO4-δ

The recently discovered, high-temperature proton conductor, La_0.99Sr_0.01NbO_4-δ, was used as a support for the electrochemical promotion of a platinum catalyst. Ethylene oxidation was used as a probe reaction in the temperature range 350-450 °C. Moderate non-Faradaic rate modification, attributable to a protonic promoting species, occurred under negative polarisation; some permanent promotion was also observed. In oxidative atmospheres, both the p_O2 of the reaction mixture and the temperature influenced the type and magnitude of the observed rate modification. Rate-enhancement values of up to ρ = 1.4 and Faradaic-efficiency values approaching Λ = -100 were obtained. Promotion was observed under positive polarisation and relatively dry, oxygen-rich atmospheres suggesting that some oxygen ion conductivity may occur under these conditions. Impedance spectroscopy performed in atmospheres of 4 kPa O₂/N₂ and of 5 kPa H₂/N₂ under dry and slightly humidified (0.3 kPa H₂O) conditions indicated that the electrical resistivity is heavily dominated by the grain-boundary response in the temperature range of the EPOC studies; much lower grain-boundary impedances in the wetter conditions are likely to be attributable to proton transport. © 2009 Elsevier B.V. All rights reserved.