Calculating Fractional-Parentage Coefficients for Six Body System in Translational Invariant Basis

In this paper we present an independent scheme for constructing fractional parentage coefficients using symmetry group apparatus in translationally invariantmodel space, suitable for the six-particle system composed of three-particle bi-clusters, where the presented subsystems have their own intrinsic clusterization. Simple expressions for corresponding antisymmetrization procedure are presented as well as computational results.

     

The effect of oxidation on the surface-near lattice relaxation in FeNi nanoparticles

The near-surface oxidation-induced lattice relaxation and compositional changes of FeNi alloy nano-particles are investigated. Using a newly developed transfer system, the particle structure was characterised by means of aberration-corrected HR-TEM prior to exposing the particles to ambient air. This allows for a comparison of oxidised and un-oxidised particles, respectively. Independent of the oxidation, the surface-near and/or interface-near metal lattice was found to be expanded by up to 3%. EELS profiles clearly reveal an enrichment of Fe at the particle surfaces. MD simulations in combination with HR-TEM contrast simulations were conducted to investigate the effect of the Fe enrichment on the structural relaxation. The results show that a surface-near over-stoichiometric enrichment of Fe indeed causes a dilation that counteracts a compression of the lattice at the particle surface as obtained for homogeneously alloyed particles. Besides, the large lattice mismatch between the metallic cores and the NiFe₂O₄ shells causes the formation of step dislocations in the close vicinities of the interface. In essence, the surface-near lattice relaxation in oxide free particles is found to be due to a segregation of Fe to the surface, whereas in the case of shell–core particles, no systematic influence of the oxide on the lattice relaxation was found.     

Vibro-Acoustic Response of a Pipe Excited by a Turbulent Internal Flow

This article presents an experimental study of the vibro-acoustic response of a pipe excited by a fully-developed turbulent air flow. First, the wall pressure field acting on the internal pipe wall is investigated. The power spectral density of the wall pressure fluctuations is analyzed after cancellation of contaminating background noise. The convection velocity and correlation lengths are calculated from measured cross-spectra, and the cross-spectra are expressed in Corcos model form. Second, the vibro-acoustic response of the pipe is analyzed by referring to the structural modes of the pipe. This revised version was published online in July 2006 with corrections to the Cover Date.     

Band-dependent quasiparticle dynamics in the hole-doped Ba-122 iron pnictides

We report on band-dependent quasiparticle dynamics in the hole-doped Ba-122 pnictides measured by ultrafast pump-probe spectroscopy. In the superconducting state of the optimal and over hole-doped samples, we observe two distinct relaxation processes: a fast component whose decay rate increases linearly with excitation density and a slow component whose relaxation is independent of excitation strength. We argue that these two components reflect the recombination of quasiparticles in the two hole bands through intraband and interband processes. We also find that the thermal recombination rate of quasiparticles increases quadratically with temperature in all samples. The temperature and excitation density dependence of the decays indicates fully gapped hole bands and nodal or very anisotropic electron bands.     

Investigation of Ti/CuO interface by X-ray photoelectron spectroscopy and atomic force microscopy

The Ti/CuO interface has been studied by the techniques of X-ray photoelectron spectroscopy and atomic force microscopy. Thin films of titanium were deposited on a CuO substrate at room temperature by the e-beam technique. The photoelectron spectra of titanium and copper were found to exhibit significant chemical interaction at the interface. The titanium overlayer was observed to get oxidized to TiO₂, while the CuO was observed to get reduced to elemental copper. This chemical interaction was observed to occur until a thickness of 7 nm of the titanium overlayer. For thicknesses greater than this value, the presence of unreacted titanium in the sample was detected. Barrier characteristics at the Ti/CuO interface were also carried out for substrate temperatures of 300°C, 400°C, 500°C, and 600°C as a function of the titanium overlayer thickness. A linear trend in the barrier thickness of the overlayer was observed between 400°C and 600°C substrate temperatures. The atomic force microscopy micrographs of the unannealed samples depicted layer-by-layer growth of elemental titanium on copper. At the Ti/CuO interface in such samples, the micrographs exhibited island formation of TiO₂ corresponding to the Volmer-Weber growth model. This formation has been interpreted as the relaxation in the strain energy. The percentage coverage of the underlying substrate by the TiO₂ islands showed a linear trend for the thicknesses of the titanium overlayer investigated. The average size of these islands also showed a linear trend as a function of the thickness of the overlayer.     

Resonant gravimetric immunosensing based on capacitive micromachined ultrasound transducers

High-frequency (40 MHz) and low-frequency (7 MHz) capacitive micromachined ultrasound transducers (CMUT) were fabricated and tested for use in gravimetric detection of biomolecules. The low-frequency CMUT sensors have a gold-coated surface, while the high-frequency sensors have a silicon nitride surface. Both surfaces were functionalized with bovine leukemia virus antigen gp51 acting as the antigen. On addition of an a specific antibody labeled with horseradish peroxidase (HRP), the antigen/antibody complex is formed on the surface and quantified by HRP-catalyzed oxidation of tetramethylbenzidine. It has been found that a considerably smaller quantity of immuno complex is formed on the high frequency sensor surface. In parallel, the loading of the surface of the CMUT was determined via resonance frequency and electromechanical resistance readings. Following the formation of the immuno complexes, the resonance frequencies of the low-frequency and high-frequency sensors decrease by up to 420 and 440 kHz, respectively. Finite element analysis reveals that the loading of the (gold-coated) low frequency sensors is several times larger than that on high frequency sensors. The formation of the protein film with pronounced elasticity and stress on the gold surface case is discussed. We also discuss the adoption of this method for the detection of DNA using a hybridization assay following polymerase chain reaction. Figure

Resonant gravimetric immunosensing with six-channel, 7 MHz capacitive micromachined ultrasound transducer (CMUT). Initial modification by antigen gp51 builds the protein layer with 13.2 GPa elasticity modulus. This increases the resonance frequency of CMUT, which is decreasing after immune complex with antibody is established.     

Structural characterization of oxidized lumiflavin hydrochloride hydrate: Comparison with the hydrogen bonding at the cofactor of flavoproteins

In order to examine the possibility of hydrogen bonding around the flavin ring, an X-ray diffraction study of the title compound was undertaken. Crystals of lumiflavin hydrochloride hydrate [2(C₁₃H₁₂N₄O₂) 4 HCl 7 H₂O] are triclinic, space group ,Z=2,a=11.064(1),b=17.903(1),c=9.891(1)Å, =111.9(6), -96.4(8), =91.6(7)°. We present the crystal structure of this compound and compare it with other flavin derivatives and with the structure of the active site of some flavoproteins.     

Catalyst‐Free Formal Thioboration to Synthesize Borylated Benzothiophenes and Dihydrothiophenes

The first ring‐forming thioboration reaction of C?C π bonds is reported. This catalyst‐free method proceeds in the presence of a commercially available external electrophilic boron source (B‐chlorocatecholborane) in good to high yields. The method is scalable and tolerates a variety of functional groups that are intolerant of other major borylation methods. The resulting borylated benzothiophenes participate in a variety of in situ derivatization reactions, showcasing that these borylated intermediates do not need to be isolated prior to downstream functionalization. This methodology has been extended to the synthesis of borylated dihydrothiophenes. Mechanistic experiments suggest that the operative mechanistic pathway is through boron‐induced activation of the alkyne followed by electrophilic cyclization, as opposed to S?B σ bond formation, providing a mechanistically distinct pathway to the thioboration of C?C π bonds.