RBS study of diffusion under strong centrifugal force in bimetallic Au/Cu thin films

The effect of the strong centrifugal force, mega-gravity (MG) on inter-diffusion between Au and Cu thin films was studied by using Au(60 nm)/Cu(500 nm)/α-Al₂O₃ (0 0 0 1) films. The Rutherford backscattering analysis of the Au and Cu depth profiles shows that Cu atoms diffuse through the Au layer, resulting in the formation of the Cu layer on the surface under both the thermal annealing at 220 °C and the application of 0.61 × 10⁶ G at 220 °C. The results indicate that the MG application enhances the layer thickness of the Cu layer on the surface.     

Basic operation of novel ferroelectric CMOS circuits

A nonvolatile ferroelectric complementary metal-oxide-semiconductor (CMOS) circuit with both logic and memory functions is proposed as a new application of ferroelectric field effect transistors. The logic and memory operations of a NOT-logic ferroelectric CMOS device is demonstrated. Nondestructive readings of high and low output voltage levels of the device were performed. Data retention was measured up to 10⁵ s (1.2 days).     

Dissection of centromeric DNA from yeast Yarrowia lipolytica and identification of protein-binding site required for plasmid transmission

In a dimorphic yeast, Yarrowia lipolytica, replicative plasmids can be established only in the coexistence of the replication origin (ORI) and centromere (CEN) from its own chromosomal DNA. Although six CEN sequences so far isolated from this yeast exhibit no similarity with conventional CEN DNA elements from other budding yeasts, they are confined within short regions (approximately 0.2 kb) and contain various conserved sequence blocks. We surveyed here a CEN1-1 sequence on an ORI-containing plasmid by deletion and site-directed mutagenesis, and found a partial palindrome, CCTAATTTGG designated DS9, to be an essential element for high-efficiency transformation. In particular, point mutations that alter symmetry and/or length of the palindrome abrogated the activity of CEN1-1. Gel mobility shift assay of CEN1-1 DNA fragments incubated with Y. lipolytica nuclear proteins revealed four bands corresponding to protein-DNA complexes, whereas the mutations within DS9 that disabled transformation also abolished the formation of part of these complexes, depending on particular mutations. These results demonstrate that the palindrome is a binding site for specific protein(s) necessary for plasmid transmission in Y. lipolytica.     

Control of threshold voltage of organic field-effect transistors by space charge polarization

We demonstrate organic field-effect transistors (OFETs) with an ion-dispersed polymer for the gate dielectrics. By applying external electric field (V_ex), the dispersed ions can migrate by electrophoresis and separated ion pairs form space charge polarization in the gate dielectrics. After V_ex was applied, the drain current is increased over 7 times and threshold voltage is decreased from − 12.9 V to − 2.9 V. The shift direction of V_th is controllable by the polarity of the V_ex. Results of ultraviolet/visible differential absorption study reveal that the active layer of OFETs is charged not only electrostatically but electrochemically with increasing the time after V_ex was applied.     

An organic nonvolatile memory using space charge polarization of a gate dielectric

We realize a nonvolatile and rewritable memory effect in an organic field-effect transistor (OFET) structure using polymethylmethacryrate (PMMA) dispersed with 10-methyl-9-phenylacridinium perchlorate (MPA⁺ClO₄⁻) as a gate dielectric. Applying a voltage between a top source-drain electrode and a bottom gate electrode induces electrophoresis of two ions of MPA⁺ and ClO₄⁻ towards the corresponding electrodes in the memory devices. The drain currents of the memory devices markedly increase from 10^− 9 A to 10^− 2 A under no gate voltage condition due to the strong space charge polarization effect. Our memory devices have excellent electrical bistability and retention characteristics, i.e. the memory on/off ratio reached 10⁷ and the drain current maintained 40% of the initial value after 10⁴ s.     

Determination of 4-hydroxycoumarin rodenticides in animal products, fishery products, and honey by liquid chromatography-tandem mass spectrometry

A sensitive and selective method for the determination of 4-hydroxycoumarin-type rodenticides (warfarin, coumatetralyl, bromadiolone, and brodifacoum) in animal products, fishery products, and honey was developed. 4-Hydroxycoumarin rodenticides were extracted with acidified acetone, and the crude extract was purified by liquid-liquid partitioning followed by PSA column cleanup. Gradient liquid chromatographic separation was performed by using an Inertsil ODS-4 column, with methanol and water containing ammonium acetate as the mobile phase. Detection was carried out on a tandem mass spectrometer with electrospray ionization in the negative mode. Average recoveries from bovine muscle, bovine liver, bovine fat, swine muscle, salmon, eel, freshwater clam, egg, milk, and honey spiked at 0.0005-0.001 mg/kg were in the range of 79-108%, and the relative standard deviations were 2-8%. The limits of quantitations of the developed method were 0.0005 mg/kg for brodifacoum, 0.001 mg/kg for warfarin, coumatetralyl, and bromadiolone.     

A sensitive analytical method for six aflatoxins in rainbow trout muscle and liver

A highly sensitive analysis method for six aflatoxins (aflatoxin B?, B?, G?, G?, M? and aflatoxicol) in rainbow trout muscle and liver was developed. Aflatoxins (AFs) were extracted with acetonitrile-water (9 : 1), purified on an immunoaffinity column, and subjected to HPLC with fluorescence detection after post-column photochemical derivatization. The recoveries of AFs at 0.05 μg/kg spiking levels were 71.4-82.4% in muscle and 80.1-93.0% in liver, and the repeatability relative standard deviations (RSDr) were 0.87-4.6% in muscle and 2.0-6.2% in liver. Limits of quantitation (LOQs) and limits of detection(LODs)of AFs were estimated to be 0.004-0.029 μg/kg, and 0.002-0.012 μg/kg, respectively.     

Observation of Magnetic‐Switching and Multiferroic‐Like Behavior of Co Nanoparticles in a C60 Matrix

A novel magnetoelectric effect is found to appear in a C₆₀‐Co nanocomposite. Although Co is well‐known as a ferromagnet, its nanoparticles embedded in a C₆₀ matrix can exhibit multiferroic‐like behavior, i.e., an electric field controls magnetic alignment of the nanoparticles and a magnetic field controls their charged states. This novel effect enables a strong magnetic switching effect for which the on/off ratio is ca. 10⁴. Such an effect has been expected to exist and these findings show this magnetoelectric coupling for the first time.     

Influence of press temperature on the properties of binderless particleboard made from oil palm trunk

The objective of this investigation was to evaluate the properties of binderless particleboard manufactured from oil palm trunk as a function of press temperature. Particleboard samples were manufactured with a target density of 0.80 g/cm³ using press temperatures of 160 °C, 180 °C and 200 °C. The modulus of rupture, internal bond strength, water absorption and thickness swelling of the boards were determined based on Japanese Industrial Standards (JIS). Thermal gravimetric analysis, Fourier transform infrared spectroscopy and field-emission scanning electron microscopy coupled with energy dispersive X-ray analysis were employed to characterize the properties of the raw materials and the manufactured panels. The moduli of rupture of the samples were observed to increase with increasing press temperature, but they did not meet the standard values. However, the internal bond strength of the samples attained satisfactory values according to the JIS standard for all three temperature levels. Water absorption and thickness swelling of the boards decreased with increasing pressing temperature. Based on the findings in this study, increasing the pressing temperature may be considered a potential way of improving the properties of binderless particleboard.