Scanning tunneling spectroscopic evidence of crossover transition in the two-impurity Kondo problem

To explore the crossover transition in the two-impurity Kondo problem, we calculate the differential conductance (dI / dV) corresponding to scanning tunneling spectroscopy (STS) measurements of a magnetic dimer adsorbed on a metal surface covered by a decoupling layer. With the aid of the numerical renormalization group (NRG) technique, we find that the peak structure of the dI / dV spectra near the Fermi level changes gradually as a function of the adatom separation and the coupling between the adatom localized spins and the metal surface conduction band. When the coupling becomes small, the peak disappears and, instead, a dip structure appears near the Fermi level. This dip structure is the manifestation of the strong antiferromagnetic correlation between the localized spins. We conclude that the gradual change of the dI / dV structure from a peak structure to a dip structure is an evidence of the crossover transition in the two-impurity Kondo problem.     

On Taylor-series expansion methods for the second kind integral equations

In this paper, we comment on the recent papers by Yuhe Ren et al. (1999) [1] and Maleknejad et al. (2006) [7] concerning the use of the Taylor series to approximate a solution of the Fredholm integral equation of the second kind as well as a solution of a system of Fredholm equations. The technique presented in Yuhe Ren et al. (1999) [1] takes advantage of a rapidly decaying convolution kernel k(|s−t|) as |s−t| increases. However, it does not apply to equations having other types of kernels. We present in this paper a more general Taylor expansion method which can be applied to approximate a solution of the Fredholm equation having a smooth kernel. Also, it is shown that when the new method is applied to the Fredholm equation with a rapidly decaying kernel, it provides more accurate results than the method in Yuhe Ren et al. (1999) [1]. We also discuss an application of the new Taylor-series method to a system of Fredholm integral equations of the second kind.     

Ring-Closing Metathesis of Ene-Ynamide: Application to the Synthesis of Medium-Sized Cyclic Dienamide

Summary: Ring-closing metathesis (RCM) of ene-ynamide, which could be applied to the synthesis of various heterocycles containing 7- and 8-membered rings, was investigated. Ene-ynamides are easily synthesized by the known method. When a toluene solution of ene-ynamide was stirred in the presence of a catalytic amount of second-generation ruthenium carbene complex 1 under an ethylene atmosphere, RCM proceeded smoothly to provide a heterocyclic compound having a diene moiety in good to high yield. A substituent of the ynamide moiety affected the yield of the cyclized product.     

Preparation of graphene oxide-coated silk fibers through HBPAA [a molecular glue]-induced layer-by-layer self-assembly

Carbon nanomaterials recently gained extensive interests for their good application potential in composite nanomaterials because of their unique physicochemical properties. In this study, graphene oxide (GO)-coated silk fibers were fabricated through HBPAA-induced layer-by-layer (LbL) self-assembly technology. The closely adhered GOs coatings were achieved by circular incubation with solutions of hyperbranched poly (amidoamine) (HBPAA) and GOs, with HBPAA serving as the “molecular glue” that could bind single or mutilayered GOs to the surface of silk fibers. In the experiments, GOs nanosheets were synthesized by a modified Hummers method and were characterized by atomic force microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Our developed technology was able to tightly bind GOs to the silk surface and control their loading capacity. Owing to the positive charges and abundant amino end groups of HBPAA, GOs were found to be completely adsorbed onto silk surface. Therefore, their assembly would be green and controllable. The Fourier transform infrared (FTIR) spectroscopy, XPS, XRD, Thermogravimetric analyses (TGA) confirmed the attachment of HBPAA and GOs. Field mission scanning electron microscopy (FESEM) indicated that GOs closely spread on the surface of silk fibers without any self-folding though excessive stacking were observed in a small part of a silk surface with the increased density of GOs coatings. The developed LbL self-assembly technology may provide a controllable approach to coat GOs on the surface of biological fibers and graphene-based functional materials.     

Rate amplification of the two photon emission from para-hydrogen toward the neutrino mass measurement

We recently reported an experiment which focused on demonstrating the macro-coherent amplification mechanism. This mechanism, which was proposed for neutrino mass measurements, indicates that a multi-particle emission rate should be amplified by coherence in a suitable medium. Using a para-hydrogen molecule gas target and the adiabatic Raman excitation method, we observed that the two photon emission rate was amplified by a factor of more than 10¹⁵ from the spontaneous emission rate. This paper briefly summarizes the previous experimental result and presents the current status and the future prospect.     

Oxygen in Ge crystals grown by the B2O3 encapsulated Czochralski method

Local vibrations of oxygen in Ge crystals grown by the Czochralski method adopting liquid-B₂O₃ encapsulation and GeO₂ powder doping were investigated by Fourier-transform infrared spectroscopy. Strong absorption peaks at 855 cm⁻¹, originating in local vibration of interstitially dissolved oxygen O_i as Ge–O_i–Ge quasi-molecules, developed depending on the doped amount of GeO₂. Similarly, an absorption peak related to the combined vibration of Ge–O_i–Ge was found at 1264 cm⁻¹ and the conversion factor from the peak intensity to the oxygen concentration was evaluated to be 1.15×10¹⁹ cm⁻². By prolonged annealing at 350 °C an absorption peak developed at 780 cm⁻¹, indicating formation of oxygen-related thermal donors. From the variations of carrier density and oxygen concentration, one donor was found to possess about 15 O_i atoms.     

HPLC‐fluorescence determination of thiol compounds in the serum of human male and female subjects using HILIC‐mode column

High‐performance liquid chromatography–fluorescence detection using a hydrophilic interaction chromatography‐mode column (ZIC®‐HILIC) was used to determine four kinds of thiol compounds in human serum. Sera were obtained from 34 subjects for this study (17 male subjects aged 22–38 years and 17 female subjects aged 18–38 years). Serum cysteine, cysteinylglycine, glutathione, and γ‐glutamylcysteine, derivatized with ammonium 7‐fluoro‐2,1,3‐benzoxadiazole‐4‐sulfonate, were separated on the ZIC®‐HILIC column and quantified. The serum concentrations of cysteine, cysteinylglycine, glutathione and γ‐glutamylcysteine were 226 ± 4.7, 23.4 ± 1.3, 3.7 ± 0.2 and 3.2 ± 0.1 μm , respectively. In addition, the concentrations of serum thiol compounds from male subjects were significantly higher than those of the female subjects (p < 0.05). Copyright © 2014 John Wiley & Sons, Ltd.