Simple planar structure for high-performance AlInAs avalanche photodiodes

We demonstrate a high-performance AlInAs avalanche photodiode (APD) based on a novel planar diode concept. The APD features a simple planar structure without a guardring, which simplifies production making it more like a PIN photodiode process. Measured device characteristics designed for 10-Gb/s use were a dark current of 0.16 /spl mu/A, responsivity of 0.88 A/W, and a gain-bandwidth product of 120 GHz. Reliability was guaranteed by an aging test exceeding 2400 h, whose conditions were a reverse dark current of 100 /spl mu/A at 175/spl deg/C. These features and performance indicate that the AlInAs APD is highly practical.     

Improvement of Li-ion conductivity in A-site disordering lithium-lanthanum-titanate perovskite oxides by adding LiF in synthesis

La_0.56−yLi_0.33TiO_3−3yF_3y (y = 0.017, 0.05) were prepared by a conventional solid-state reaction from a mixture of La₂O₃, LiCO₃, TiO_2, and 10% excess LiF. The variation of the lattice parameter with increase of y value in La_0.56−yLi_0.33TiO_3−3yF_3y was different from that in conventional lithium-lanthanum-titanate series perovskite oxides, La_0.56−yLi_0.33+3yTiO₃. Bulk Li-ion conductivities of the La_0.56−yLi_0.33TiO_3−3yF_3y are higher than those of La_0.56-yLi_0.33+3yTiO₃. Li-ion conductivity of La_0.56−yLi_0.33TiO_3−3yF_3y (y = 0.017) was 2.30 × 10⁻³ S cm⁻¹ at 30 °C, which is, to our knowledge, one of the highest Li-ion conductivities in the oxide compounds.     

Electrochemical oxidation of cholesterol in acetonitrile leads to the formation of cholesta-4,6-dien-3-one

Cholesterol was shown to be oxidized at the glassy carbon electrode in an acetonitrile–2-propanol mixture and this oxidation reaction was applied to the determination of serum total cholesterol by high-performance liquid chromatography with electrochemical detection (K. Hojo, H. Hakamata, A. Ito, A. Kotani, C. Furukawa, Y.Y. Hosokawa, F. Kusu, J. Chromatogr. A 1166 (2007) 135–141). To gain insight into the detection mechanisms of cholesterol, an electrolytic product of cholesterol was collected and characterized by infrared spectroscopy, one- and two-dimensional nuclear magnetic resonance, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The three techniques, together with comparisons of literature spectral data, confirmed the formation of cholesta-4,6-dien-3-one. The conversion of cholesterol to cholesta-4,6-dien-3-one, a four-electron, four-proton electrochemical process, has been proposed as an electrochemical oxidation mechanism of cholesterol in acetonitrile.     

Shape-memory surface with dynamically tunable nano-geometry activated by body heat

Shape-memory surfaces with on-demand, tunable nanopatterns are developed to observe time dependent changes in cell alignment using temperature-responsive poly(?-caprolactone) (PCL) films. Temporary grooved nanopatterns are easily programmed on the films and triggered to transition quickly to permanent surface patterns by the application of body heat. A time-dependent cytoskeleton remodeling is also observed under biologically relevant conditions.     

Novel temperature-responsive polymer brushes with carbohydrate residues facilitate selective adhesion and collection of hepatocytes

Temperature-responsive glycopolymer brushes were designed to investigate the effects of grafting architectures of the copolymers on the selective adhesion and collection of hypatocytes. Homo, random and block sequences of N-isopropylacrylamide and 2-lactobionamidoethyl methacrylate were grafted on glass substrates via surface-initiated atom transfer radical polymerization. The galactose/lactose-specific lectin RCA₁₂₀ and HepG2 cells were used to test for specific recognition of the polymer brushes containing galactose residues over the lower critical solution temperatures (LCSTs). RCA₁₂₀ showed a specific binding to the brush surfaces at 37 °C. These brush surfaces also facilitated the adhesion of HepG2 cells at 37 °C under nonserum conditions, whereas no adhesion was observed for NIH-3T3 fibroblasts. When the temperature was decreased to 25 °C, almost all the HepG2 cells detached from the block copolymer brush, whereas the random copolymer brush did not release the cells. The difference in releasing kinetics of cells from the surfaces with different grafting architectures can be explained by the correlated effects of significant changes in LCST, mobility, hydrophilicity and mechanical properties of the grafted polymer chains. These findings are important for designing ‘on–off’ cell capture/release substrates for various biomedical applications such as selective cell separation.     

Multiresidue analysis of pesticides in agricultural products by GC/MS,GC-ECD and GC-FTD using acetonitrile extraction and clean-up with mini-columns

An analytical method was developed for determination of organochlorine, pyrethroid and nitrogen-containing pesticide residues in agricultural products by GC/MS, GC-ECD and GC-FTD. Pesticides were extracted with acetonitrile, and the organic layer was cleaned up on C18 and ENVI-Carb/LC-NH2 cartridges. Pesticides were determined by GC/MS, GC-ECD and GC-FTD. Detection limits of pesticides by GC/MS and GC were below 1-30 ng/g and 1-3 ng/g, respectively. Recoveries of 27 out of 53 pesticides determined by GC/MS and 47 out of 53 determined by GC were 70-120%. This method was useful for the multiresidue analysis of pesticides in agricultural products. Pesticide residues in 81 domestic crops were investigated from April 2001 to March 2002. Residues of 31 pesticides were detected from 21 crops.     

Densification of AlN using boron and carbon additives

The effects of boron and/or carbon on the densification of AlN were investigated. Sintering was promoted by adding the additives simultaneously. Thermo-chemical analysis indicated that a liquid phase composed of aluminum and boron were formed by the borothermal reduction of Al₂O₃ and AlN. Liquid phase sintering is believed to be the reason for the enhanced densification of AlN. The present investigation proposes a method to densify AlN using non-oxide sintering additives having high melting temperature (>2000 °C). The deterioration of AlN refractory is expected to be suppressed by preventing the formation of oxide grain boundary network which is vulnerable to corrosion caused by molten metal.     

Evaluation of curability and prediction of prognosis after surgical treatment for hepatocellular carcinoma by lens culinaris agglutinin-reactive alpha-fetoprotein

The MDR-3-encoded P-glycoprotein (Pgp) is highly expressed in liver and is thought to function as a hepatic transporter of phospholipids into bile. However its role, if any, in other tissues remains undefined. Although transfection experiments have indicated that it may be unable to confer drug resistance, there is evidence that it may be involved in drug resistance in certain B-cell leukaemias. To date, most work on clinical samples has been performed at the mRNA level; limited work has been performed using polyclonal antibodies raised to MDR-3 and mdr-2 (the murine equivalent of MDR-3). We have generated a new monoclonal antibody, termed 6/1G, which specifically recognises the human MDR-3 gene-encoded product. Antibody 6/1G was produced by in vitro immunisation of spleen cells from BALB/c mice with a synthetic 12-amino acid peptide. Cells from MDR-3 transgenic mice showed consistent membranous staining with antibody 6/1G. Immunoblotting with 6/1G identified a band at 170 kDa on lysates of MDR-3 transgenic cells. Preliminary results with a range of B-cell leukaemias suggest that MDR-3 Pgp positivity may be a marker for a more malignant phenotype in B-CLL. Antibody 6/1G may be useful in defining a role for MDR-3 in malignancy and drug resistance, as well as in certain liver diseases such as progressive familial intracholeostasis.     

Characterization and estimation of tunnel barrier height in metallic single-wall carbon nanotube quantum dots

A tunnel barrier height has been estimated in quantum dots (QDs) formed in metallic single-wall carbon nanotubes (SWNTs), where QDs can be fabricated simply by depositing metallic contacts on top of the nanotube. Transport measurements have been carried out in a temperature range between 1.5 and 300 K, and revealed single and multi-QD behaviors in different samples at low temperatures. The Arrhenius plot gave an activation energy of ∼6 meV for the barrier formed very likely at the metal-SWNT interface for the single QDs, and two activation energies for seemingly double dots. The latter case comes from the unintentional tunnel barrier due to defects. Discussions on the QD formation and suggestions for a higher temperature operation are given.