High Ambipolar Mobility in a Neutral Radical Gold Dithiolene Complex

A new anionic gold dithiolene complex NBu₄·[1] is synthesized from the (1‐((1,1‐biphenyl)‐4‐yl‐)‐ethylene‐1,2‐dithiolene ligand 1, and the cis and trans isomers are separated by recrystallization. The trans isomer is oxidized via electrocrystallisation to the neutral gold dithiolene complex 2. Complex 2 crystalizes in 1D chains, held together by short (3.30–3.37 Å) S–S contacts, which are packed in a herringbone arrangement in the ab‐plane. The complex exhibits semiconductor behavior (σ_RT = 1.5 × 10^?4 S cm^?1) at room temperature with a small activation energy (E_a = 0.11 eV), with greater conductivity along the stacking direction. The charge transport behavior of complex 2 is further investigated in single‐crystal field‐effect transistor (FET) measurements, the first such measurements reported for gold dithiolene complexes. Complex 2 shows incredibly balanced ambipolar behavior in the single‐crystal field‐effect transistor (SC‐FET), with high charge‐carrier mobilities of 0.078 cm² V^?1 s^?1, the highest ambipolar mobilities reported for metal dithiolene complexes. This well‐balanced behavior, along with the activated conductivity and band structure calculations, suggests that 2 behaves as a Mott insulator. The magnetic properties are also studied by superconducting quantum interference device (SQUID) magnetometry and solid state ¹H NMR, with evidence of a nonmagnetic ground state at low temperature.     

Frequency translation of light waves by propagation around an optical ring circuit containing a frequency shifter: II. Theoretical analysis

Theoretical aspects of the frequency-translation ring circuit are considered through numerical simulations. We analyze the signal and noise propagation around an optical ring circuit that contains a frequency shifter, an erbium-doped fiber amplifier and a bandpass filter (BPF). The relations between the frequency-translation limit and some important parameters such as the BPF bandwidth and the polarization state are clarified. Numerical results for the frequency-translation limit are compared with reported experiments and a frequency translation of more than 100 GHz is predicted.     

Segmentation of abnormal liver region based on earth mover’s distance between histograms with mapping of the distances by multidimensional scaling

In this paper, we propose using earth mover’s distance (EMD) to obtain the appropriate similarity between each histogram for segmentation of abnormal liver regions with mapping of the distances by multidimensional scaling. Conventionally, the similarity between each histogram is calculated by integrating the difference between each bin of the histograms. However, this similarity is unsuitable for appropriate comparison of the histograms because the number of bins for calculating the local histograms of computed tomography images varies. We used EMD to resolve this problem regarding the difference in bin numbers, and the obtained distances are used for mapping the local histograms by multidimensional scaling to low-dimensional space. In the low-dimensional space, the abnormal liver region was well segmented by support vector machine in the test datasets.     

Microbial conversion of an oil containing α-linolenic acid to an oil containing eicosapentaenoic acid

Mycelia of arachidonic acid-producing fungi belonging to the genusMortierella were found to convert an oil containing α-linolenic acid to an oil containing 5,8,11,14,17-cis-eicosapentaenoic acid (EPA). This conversion was observed when they were grown in a medium containing the oil, glucose and yeast extract at 28 C. On the screening of various oils, linseed oil, in which α-linolenic acid amounts to about 60% of the total fatty acids, was found to be the most suitable for EPA production. Under the optimal culture conditions, a selected strain,Mortierella alpina 20-17, converted 5.1% of the α-linolenic acid in the added oil into EPA, the EPA production reaching 1.35 g/l of culture broth (41.5 mg/g dry mycelia). This value corresponded to 7.1% (by weight) of the total fatty acids in the extracted lipids. The lipid was also found to be rich in arachidonic acid (12.3%). Other major fatty acids in the lipid were palmitic acid (4.4%), stearic acid (3.2%), oleic acid (13.5%), linoleic acid (13.7%), α-linolenic acid (38.5%) and γ-linolenic acid (0.9%).     

Partial oxidation of methane over silica supported molybdenum oxide catalysts

Two kinds of MoO₃/SiO₂ catalysts, MoO₃-I and MoO₃-S, were prepared by impregnation and sol-gel method, respectively. When MoO₃ loading was increased, formation of MoO₃ crystals was observed to begin at a MoO₃ loading of 8 and 16 wt% with MoO₃-I and MoO₃-S, respectively. The highest yield of formaldehyde from methane oxidation was attained also at those critical values of MoO₃ loading of 8 and 16 wt% over MoO₃-I and MoO₃-S, respectively. It is suggested that the active species for formaldehyde formation is well dispersed molybdenum oxide clusters on SiO₂ support: the optimum dispersion of the clusters affords the highest activity for formaldehyde formation.     

Dual lamellar crystal structure in poly(vinylidene fluoride)/acrylic rubber blends and its biaxial orientation behavior

The miscibility for melt-mixed poly(vinylidene fluoride) (PVDF)/acrylic rubber (ACM) blends and the crystal morphology of PVDF in the blends were investigated over the whole composition ranges by dynamic mechanical analysis (DMA), wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). DMA measurements revealed that PVDF is miscible with ACM in ACM-rich system, and partially miscible in PVDF-rich system. Two kinds of PVDF lamellar structures with different long periods were detected by SAXS and TEM for the partially miscible blends. In the miscible system, only one kind of crystal lamellae with enlarged long period is found. The two kinds of lamellar structures in the blend show different orientation behavior during the uniaxial stretching to result in a biaxial orientation. The lamellae with short long period are oriented vertical to the stretching direction, while those with large long period were found to be oriented parallel to the stretching direction.     

Production of centrifugal fields greater than 100 million times gravity

A high-speed rotation instrument to produce centrifugal fields greater than 100 million times gravity has been constructed. Small, solid, spherical high-carbon chromium steel rotors are suspended magnetically in high vacuum and spun by a rotating magnetic field. It is found that the spinning rotor explodes when the calculated average value of stress in the meridian plane reaches about 1.2 times the tensile strength of the material. The maximum speed of rotation so far achieved for more than a few days without bursting was obtained with a rotor of 1.50 mm diameter. The speed of 2.11 x 10(5) rev/s corresponded to a centrifugal field of 1.34 x 10(8) times gravity. Our instrument will find application in the study of nuclear atomic phenomena.     

Transient anodic oxidation of an Al-W alloy: effects of current ratio

Previous experiments involving stepped changes in current during anodizing of aluminium alloys have disclosed subtle transient and long-term influences of current density on film growth. The present work employs a current reduction of a factor of 10⁴, much larger than that in earlier work, to investigate the phenomena further. The findings from transmission electron microscopy of film sections disclose that the step in current leads to generation of fine light bands of film material, each about 6 nm thick, at the alloy/film and film/electrolyte interfaces. Further, the film material formed at the alloy/film interface following the step in current is generally of lighter appearance than that formed previously. The lighter film material probably contains relatively less tungsten species, and/or is of reduced density, compared with adjacent material. The greater reduction in current, compared with that of previous studies, appears to accentuate the alterations in composition and/or density of film material.     

Examination of surface films on aluminium and its alloys by low-voltage scanning and scanning transmission electron microscopy

The potential of low-voltage, high-resolution scanning and scanning transmission electron microscopy (SEM/STEM) for morphological characterization of various surface insulating films on aluminium and its alloys has been assessed by examination of porous anodic films, barrier anodic films and corrosion product layers. The characterization shows clearly the value of the approaches, particularly the ability to image directly fine details of appropriately-prepared aluminium surfaces that have usually required examination by transmission electron microscopy (TEM). Such ready characterization assists mechanistic understanding of the contributions of the macroscopic surface and flaws or second phase to the filming and corrosion processes. Further, the approaches are applicable to other materials where such understanding was limited by the sample preparation routes available for TEM.     

Molecular Dynamics Simulation of Flattening Process of a High-Temperature, High-Speed Droplet—Influence of Impact Parameters

Three-dimensional molecular dynamics simulation was conducted to clarify at an atomic level the flattening process of a high-temperature droplet impacting a substrate at high speed. The droplet and the substrate were assumed to consist of pure aluminum, and the Morse potential was postulated between a pair of aluminum atoms. In this report, the influence of the impact parameters such as the droplet velocity and the droplet diameter on flattening behavior were analyzed. As a result, the following representative conclusions were obtained: (a) the flattening ratio increases in proportion to the droplet velocity and the droplet diameter; (b) the flattening ratio for nanosized droplet can be reorganized by the same dimensionless parameters of the proper physical properties, such as the viscosity and the surface tension, as those used in the macroscopic flattening process. This article is an invited paper selected from presentations at the 2007 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Global Coating Solutions, Proceedings of the 2007 International Thermal Spray Conference, Beijing, China, May 14-16, 2007, Basil R. Marple, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain Montavon, Ed., ASM International, Materials Park, OH, 2007.