Acoustic inspection of bond strength of steel-reinforced mortar after exposure to elevated temperatures

In order to evaluate the bond strength between the reinforcement and concrete after fire damage, a combination of acoustic through-transmission and pull-out tests were used. Previous studies have shown a 25% decrease in the ultrasonic pulse velocity at 90% of the maximum load at room temperature. The specimens were kept in the oven at an elevated temperature for 1, 2, or 3 h. They were then removed and cooled to room temperature. Inspection was conducted using a high-power ultrasonic pulse velocity system while a pull-out load was applied. The correlation between preheated temperature, acoustic wave velocity, and the applied load was analyzed. Initial results show that bond strength and pulse velocity decreased substantially as the temperature or the heating time increased.     

Stabilization of plutonium(III) in the Preyssler polyoxometalate

The Na(+) ion encapsulated within the Preyssler heteropolyoxoanion, [NaP5W30O110](14-), was exchanged with Pu(III) under hydrothermal conditions to obtain [Pu(III)P5W30O110](12-) (abbreviated [PuPA](12-)) with hybrid electrochemical properties resulting from the combination of the key redox behaviors of the Pu cation and the P-W-O anion. The electroanalytical chemistry of this two-center, multielectron redox system in a 1 M HCl electrolyte shows that Pu(III) is oxidized to Pu(IV) at the half-wave potential, E(1/2), of +0.960 V versus Ag/AgCl, which is 0.197 V more positive than the corresponding electrode potential for the Pu(III) aqua ion also in 1 M HCl, indicating the stabilization of the trivalent Pu cation by its encapsulation in the Preyssler polyoxometalate (POM). This effect is uncommon in actinide-POM chemistry, wherein electrode potential shifts of the opposite nature (to more negative values), leading to the stabilization of the tetravalent ions by complexation, are renowned. Moreover, in cyclic voltammetry measurements of the Pu(III) aqua ion and [PuPA](12-), the peak currents, i(p), for the one-electron Pu(III)/Pu(IV) processes show different dependencies with the scan rate, nu. The former shows proportionality with nu(1/2), indicating freely diffusing species, whereas the latter shows proportionality with nu, indicating a surface-confined one. The first of the five successive two-electron, W-centered reduction processes in [PuPA](12-) occurs at E(1/2) = -0.117 V versus Ag/AgCl, which is 1.077 V less than the E(1/2) for the Pu(III)/Pu(IV) oxidation, thereby providing an experimental, electrochemical measure of the highest occupied molecular orbital/lowest unoccupied molecular orbital energy gap, which compares well with values previously obtained by density-functional theory, complete active space-self consistent field, and post-Hartree-Fock calculations for a series of M(n+)-exchanged systems, [MPA](n-15) for 1 < or = n < or = 4 (Fernandez, J. A.; Lopez, X.; Bo, C.; de Graff, C.; Baerends, E. J.; Poblet, J. M. J. Am Chem. Soc. 2007, 129, 12244-12253). It was not possible to prepare the Np-exchanged Preyssler anion in the manner of [PuPA](12-), because of the instability of tri- and tetravalent Np to oxidation and the formation of the neptunyl(V) ion, which also could not be exchanged for Na(+).     

Size-restricted proton transfer within toluene-methanol cluster ions

To understand the interaction between toluene and methanol, the chemical reactivity of [(C6H5CH3)(CH3OH) n=1-7](+) cluster ions has been investigated via tandem quadrupole mass spectrometry and through calculations. Collision Induced Dissociation (CID) experiments show that the dissociated intracluster proton transfer reaction from the toluene cation to methanol clusters, forming protonated methanol clusters, only occurs for n = 2-4. For n = 5-7, CID spectra reveal that these larger clusters have to sequentially lose methanol monomers until they reach n = 4 to initiate the deprotonation of the toluene cation. Metastable decay data indicate that for n = 3 and n = 4 (CH3OH)3H(+) is the preferred fragment ion. The calculational results reveal that both the gross proton affinity of the methanol subcluster and the structure of the cluster itself play an important role in driving this proton transfer reaction. When n = 3, the cooperative effect of the methanols in the subcluster provides the most important contribution to allow the intracluster proton transfer reaction to occur with little or no energy barrier. As n >or= 4, the methanol subcluster is able to form ring structures to stabilize the cluster structures so that direct proton transfer is not a favored process. The preferred reaction product, the (CH3OH)3H(+) cluster ion, indicates that this size-restricted reaction is driven by both the proton affinity and the enhanced stability of the resulting product.     

Solid-state highly fluorescent diphenylaminospirobifluorenylfumaronitrile red emitters for non-doped organic light-emitting diodes

Bright (maximum 11,000 cd m(-2) and 500 cd m(-2) at 20 mA cm(-2)) and efficient (maximum external quantum efficiency of 3.1% at 1 mA cm(-2)) red (CIE, x = 0.66, y = 0.34) organic light-emitting diodes (OLEDs) employ arylaminospirobifluorene-substituted fumaronitriles as the novel non-dopant red emitter.     

Cationic bis-cyclometallated iridium(III) phenanthroline complexes with pendant fluorenyl substituents: synthesis, redox, photophysical properties and light-emitting cells

We report the synthesis, characterisation, photophysical and electrochemical properties of a series of cationic cyclometallated Ir(III) complexes of general formula [Ir(ppy)(2)(phen)]PF(6) (ppy=2-phenylpyridine, phen=a substituted phenanthroline). A feature of these complexes is that the phen ligands are substituted with one or two 9,9-dihexylfluorenyl substituents to provide extended pi conjugation, for example, the 3-[2-(9,9-dihexylfluorenyl)]phenanthroline and 3,8-bis[2-(9,9-dihexylfluorenyl)]phenanthroline ligands afford complexes 6 and 9, respectively. A single-crystal X-ray diffraction study of a related complex 18 containing the 3,8-bis(4-iodophenyl)phenanthroline ligand, revealed an octahedral coordination of the Ir atom, in which the metallated C atoms of the ppy ligands occupy cis positions. The complexes 6 and 9 displayed reversible oxidation waves in cyclic voltammetric studies (E(ox)(1/2)=+1.18 and +1.20 V, respectively, versus Ag/Ag(+) in CH(2)Cl(2)) assigned to the metal-centred Ir(III)/Ir(IV) couple. The complexes exhibit strong absorption in the UV region in solution spectra, due to spin-allowed ligand-centred (LC) (1)pi-pi* transitions; moderately intense bands occur at approximately 360-390 nm which are red-shifted with increased ligand length. The photoluminescence spectra of all the complexes were characterised by a broad band at lambda(max) approximately 595 nm assigned to a combination of (3)MLCT and (3)pi-->pi* states. The long emission lifetimes (in the microsecond time-scale) are indicative of phosphorescence: the increased ligand conjugation length in complexes 9 and 17 leads to increased lifetimes for the complexes (tau=2.56 and 2.57 micros in MeCN, respectively) compared to monofluorenyl analogues 6 and 15 (tau=1.43 and 1.39 micros, respectively). DFT calculations of the geometries and electronic structures of complexes 6', 9' (for both singlet ground state (S(0)) and triplet first excited (T(1)) states) and 18 have been performed. In the singlet ground state (S(0)) HOMO orbitals in the complexes are spread between the Ir atom and benzene rings of the phenylpyridine ligand, whereas the LUMO is mainly located on the phenanthroline ligand. Analysis of orbital localisations for the first excited (T(1)) state have been performed and compared with spectroscopic data. Spin-coated light-emitting cells (LECs) have been fabricated with the device structures ITO/PEDOT:PSS/Ir complex/Al, or Ba capped with Al (ITO=indium tin oxide, PEDOT=poly(3,4-ethylenedioxythiophene), PSS=poly(styrene) sulfonate). A maximum brightness efficiency of 9 cd A(-1) has been attained at a bias of 9 V for 17 with a Ba/Al cathode. The devices operated in air with no reduction in efficiency after storage for one week in air.     

Molecular genetic mining of the Aspergillus secondary metabolome: discovery of the emericellamide biosynthetic pathway

The recently sequenced genomes of several Aspergillus species have revealed that these organisms have the potential to produce a surprisingly large range of natural products, many of which are currently unknown. We have found that A. nidulans produces emericellamide A, an antibiotic compound of mixed origins with polyketide and amino acid building blocks. Additionally, we describe the discovery of four previously unidentified, related compounds that we designate emericellamide C-F. Using recently developed gene targeting techniques, we have identified the genes involved in emericellamide biosynthesis. The emericellamide gene cluster contains one polyketide synthase and one nonribosomal peptide synthetase. From the sequences of the genes, we are able to deduce a biosynthetic pathway for the emericellamides. The identification of this biosynthetic pathway opens the door to engineering novel analogs of this structurally complex metabolite.     

Conversion of Polyethylenes into Fungal Secondary Metabolites

Waste plastics represent major environmental and economic burdens due to their ubiquity, slow breakdown rates, and inadequacy of current recycling routes. Polyethylenes are particularly problematic, because they lack robust recycling approaches despite being the most abundant plastics in use today. We report a novel chemical and biological approach for the rapid conversion of polyethylenes into structurally complex and pharmacologically active compounds. We present conditions for aerobic, catalytic digestion of polyethylenes collected from post-consumer and oceanic waste streams, creating carboxylic diacids that can then be used as a carbon source by the fungus Aspergillus nidulans. As a proof of principle, we have engineered strains of A. nidulans to synthesize the fungal secondary metabolites asperbenzaldehyde, citreoviridin, and mutilin when grown on these digestion products. This hybrid approach considerably expands the range of products to which polyethylenes can be upcycled.     

The study of B→K(*)l+l- decays in family non-universal Z' models

In a combined investigation of B→K^(*)l⁺l^- decays, constraints on the related couplings in family non-universal Z' models are derived. We find that within the allowed parameter space, the recently observed forward-backward asymmetry in the B→K^(*)l⁺l^- decay can be explained by flipping the signs of the Wilson coefficients C₉^eff and C₁₀. With the obtained constraints, we also calculate the branching ratio of the B_s→μ⁺μ^- decay. The upper bound of our prediction is nearly an order of magnitude smaller than the upper bound given by the CDF Collaboration recently.     

Immunoassay of plasmonic gold‐nanoparticle clusters: Plasmon coupling effects for Parkinson biomarker detection

A simple signal‐on plasmonic optical assay for the detection of the Parkinson biomarker using gold‐nanoparticle clusters (AuNCs) for signal amplification is presented. This approach is based on the improvement of the optical density (OD) change of the plasmonic band of a localized surface plasmon resonance (LSPR) Au nanoparticle (AuNP) sensor interface using Au NCs conjugated antibodies. The amplification results in a 260‐fold improvement in concentration detection, from 1,000 ng/mL (unlabeled antibody) to 3.8 ng/mL (antibody‐conjugated AuNCs). The sensitivity enhancement can be ascribed to the further plasmonic coupling between the antibody‐conjugated AuNCs and the AuNPs on the LSPR interface and the enhanced amount of target molecule bound to the bioassay. This AuNCs‐assisted signal amplification strategy allows for improving the sensitivity of the plasmon‐based bioassays and can be extended to other optical‐based diagnostic technologies. Importantly, the simple detecting procedure and protocol assembly make it competitive with other existing sensing technologies such as ELISA, allowing for practical usage in clinical diagnostics.     

Propagation of Solitary Pulses in Optical Fibers with Both Self-Steepening and Quintic Nonlinear Effects

Pulse dynamics and stability in optical fibers in the presence of both self-steepening and quintic nonlinear effects are analyzed. Propagating profiles of the quintic derivative nonlinear Schrodinger model are isolated via two invariants of motion. The resulting canonical equation admits exact periodic propagating patterns in terms of the Jacobi elliptic functions, and solitary pulses are recovered in the long wave limit, i.e. degenerate cases of periodic profiles where each pulse is widely separated from the adjacent ones. Two families of such exact wave profiles are identified. The first one has a precise constraint concerning the magnitude of self-steepening and quintic nonlinear effects, while the second one permits more freedom. The reduction to the well established temporal soliton in an optical fiber waveguide in the absence of self-steepening and quintic nonlinearity is demonstrated explicitly. Numerical simulations are performed to identify regimes of parameter values where robust propagation patterns exist.