Multi-staged nonlinear compensation in coherent receiver for 12 015 km WDM transmission of 10-ch x 111 Gbit/s no-guard-interval co-OFDM

It is experimentally shown that employing multi-staged reverse self-phase-modulation in a coherent receiver compensates for waveform distortion due to self-phase-modulation including the inter-polarisation nonlinearity of polarisation-division multiplexing and inter-subcarrier nonlinearity of orthogonal frequency division multiplexing. This scheme extends the transmission distance 1.25-fold under an uncompensated dispersion map to suppress cross-phase-modulation, and a 10-channel times111 Gbit/s OFDM signal is successfully transmitted 12times015 km at the spectrum efficiency of 2.0 bit/s/Hz with a 1.0timesdB penalty reduction.     

A study of film thickness dependence of the graphitizability of PMDA–ODA polyimide-derived carbon film

PMDA–ODA (pyromellitic dianhydride–4,4′-oxydianiline) polyimide (PI) films with thickness of 2–26 μm were synthesized and heat-treated at 2200–2500°C. The effect of film thickness on both the graphitizability of the PI-derived carbon film and the crystalline organization of the initial PI film was investigated by X-ray diffraction. The degree of graphitization of the resultant carbon film was observed to increase with decreasing initial PI film thickness, corresponding to the film thickness dependence of the crystalline ordering in the initial PI films. Structural factors related to PI film thickness are discussed for understanding the graphitizability of the resultant carbon.     

Characterization of Electrical Properties of Li(FexAl1−x)5O8 Solid Solutions by Impedance Spectroscopy

To examine polaronic transport properties in Li(Fe _x Al_{1− x} )₅O₈ spinel solid solutions, a scaling analysis for their conductivity spectra and modulus spectra was performed. As in the case of ionic conductors, two significant parameters of a crossover frequency and a power-law exponent were extracted from the conductivity spectra which displayed the universal dynamic response behavior. Both the mobility and the concentration of carriers were successfully determined from the crossover frequency. The power-law exponent and the stretching parameter obtained from the modulus spectra varied with composition, implying that the increase in Fe concentration would enhance the Coulomb interactions between small polarons.     

Degradation analysis of dye-sensitized solar cell module after long-term stability test under outdoor working condition

Using Raman spectroscopy in addition to electrochemical impedance spectroscopy, we have clarified the deteriorated components of dye-sensitized solar cells (DSCs) module after the longest durability test in the world under outdoor working condition for ～2.5 years. It was confirmed that the N719 dye-adsorbed TiO₂ electrode and carbon counter electrode were almost stable; therefore, the photocurrent (Jsc) was maintained during the outdoor working. The photovoltages (Voc) and the filling factors (FF) slightly decreased due to the increase of the Nernst diffusion impedance of triiodide (I₃^?), resulting from the change of the components in the electrolyte.     

Structure of the ring cleavage product of 1-hydroxy-2-naphthoate, an intermediate of the phenanthrene-degradative pathway of Nocardioides sp. strain KP7

1-Hydroxy-2-naphthoate (compound I) is a metabolite of the phenanthrene-degradative pathway in Nocardioides sp. strain KP7. This singly hydroxylated aromatic compound is cleaved by 1-hydroxy-2-naphthoate dioxygenase. In this study, the structure of the ring cleavage product generated by the action of homogeneous 1-hydroxy-2-naphthoate dioxygenase was determined upon separation by high-performance liquid chromatography at pH 2.5 by using nuclear magnetic resonance (NMR) and mass spectroscopic techniques. The ring cleavage product at this pH existed in equilibrium between two forms, 2-oxo-3-(3-oxo-1,3-dihydro-1-isobenzofuranyl)propanoate (compound III) and 2,2-dihydroxy-3-(3-oxo-1, 3-dihydro-1-isobenzofuranyl)propanoate (compound IV). After the pH of the solution was raised to 7.5, the structure of the major species became (E)-4-(2-carboxylatophenyl)-2-oxo-3-butenoate (compound II; common name, trans-2'-carboxybenzalpyruvate), which was in equilibrium with compound III. Direct monitoring of the enzymatic formation of the ring cleavage product by 1H-NMR in a deuterated potassium phosphate buffer (pH 7.5) detected only compound II as a product, and the proton on carbon 3 of compound II was not exchanged with deuterium. Thus, compound II is likely to be the first stable product of dioxygenation of 1-hydroxy-2-naphthoate.     

Annealing induced phosphorus protrusion into thin-oxide films from heavily phosphorus-doped silicon (100)

Phosphorus (P) protrusion into thin-oxide film from heavily P-doped Si (100) upon annealing was investigated using X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). After annealing at 750 °C, the P was segregated at the SiO₂/Si interface and its concentration decayed exponentially toward both the thin-oxide film and the substrate. The chemical state of protruded-P in the oxide was nearly elemental. After annealing, the AFM images of the sample surface showed that some of the plateaus grew in height while maintaining their lateral shape. The total increment volume of the grown plateaus corresponded roughly to the volume of protruded-P in the oxide film estimated by XPS.     

Neutron capture cross section measurements of 151,153Eu using a pair of C6D6 detectors

We have measured the neutron capture cross sections of ¹⁵¹Eu and ¹⁵³Eu by the time-of-flight (TOF) method in the range from 0.005 eV to keV region using the Kyoto University Research Reactor Institute - Linear Accelerator (KURRI-LINAC). We employed a pair of C₆D₆ liquid scintillators for the prompt capture γ-ray measurement. The pulse-height weighting technique was employed to obtain the capture yields from the γ-ray spectra of ^151,153Eu. The obtained thermal cross sections at 0.0253 eV are 9051 ± 683 b for ¹⁵¹Eu and 364 ± 44 b for ¹⁵³Eu, respectively. The resonance integrals have been derived as 3490 ± 162 b for ¹⁵¹Eu and 1538 ± 106 b for ¹⁵³Eu.

The obtained capture cross sections were compared with the previously reported experimental data and the evaluated data. The evaluated data in JENDL-4.0 and JEFF-3.2 show good agreement with the present experiment results of ¹⁵¹Eu, however, the evaluated data in ENDF/B-VII.1 are larger than the present experiment results of ¹⁵¹Eu about 10% to 20% in the energy region from 0.03 to 0.2 eV. For the neutron capture cross sections of ¹⁵³Eu, the evaluated data in ENDF/B-VII.1 and Widder's data are in good agreement with the present results in the energy region below 0.35 eV.     

Scaling dependence of electron transport in nano-scale Schottky barrier MOSFETs

The scaling dependence of electron transport in the double-gated Schottky barrier MOSFET (DG-SBT) below 10 nm is investigated in the framework of quantum transport theory, using non-equilibrium Green’s function method. Simulation results show that the current-voltage characteristics in ultra-small DG-SBT are characterized by both resonant and direct tunneling effects. The electron potential in the 10-nm-scale DG-SBT surrounded by Schottky barriers acts as a resonant cavity and produce a negative differential resistance due to resonant tunneling effect. While, further scaling shallows the depth of the cavity and makes it difficult to form resonance levels. Hence, at the scaling limit, direct tunneling currents simply dominate the current-voltage characteristics of DG-SBT.     

Rapid synthesis of Ag@Ni core-shell nanoparticles using a microwave-polyol method

Mixtures of AgNO₃ and NiSO₄·6H₂O, NiCl₂·6H₂O, or Ni(NO₃)₂·6H₂O were reduced in ethylene glycol (EG) in the presence of NaOH and poly(vinylpyrrolidone) (PVP) under microwave (MW) heating for 10 min. Then, we succeeded in the synthesis of Ag core-Ni shell nanoparticles, denoted as Ag@Ni, in high yield. The formation of Ag@Ni particles was confirmed using energy dispersed X-ray spectroscopic (EDS) measurements and selected area electron diffraction (SAED) patterns. The growth mechanism of Ag@Ni is discussed. The UV-Vis spectra of Ag@Ni were similar to those of Ni particles.