Hall Effect in Bulk‐Doped Organic Single Crystals

The standard technique to separately and simultaneously determine the carrier concentration per unit volume (N , cm^?3) and the mobility (μ) of doped inorganic single crystals is to measure the Hall effect. However, this technique has not been reported for bulk‐doped organic single crystals. Here, the Hall effect in bulk‐doped single‐crystal organic semiconductors is measured. A key feature of this work is the ultraslow co‐deposition technique, which reaches as low as 10^?9 nm s^?1 and enables us to dope homoepitaxial organic single crystals with acceptors at extremely low concentrations of 1 ppm. Both the hole concentration per unit volume (N , cm^?3) and the Hall mobility (μ_H) of bulk‐doped rubrene single crystals, which have a band‐like nature, are systematically observed. It is found that these rubrene single crystals have (i) a high ionization rate and (ii) scattering effects because of lattice disturbances, which are peculiar to this organic single crystal.     

Flow Conditions of Undular Hydraulic Jumps in Horizontal Rectangular Channels

The flow conditions of undular jumps for fully developed inflow condition have been investigated systematically. If the inflow Froude number is larger than 1.2, an undular jump has lateral shock waves near the toe of the jump. For a narrow channel, the shock waves cross upstream of the first wave crest, and the flow conditions of undular jumps depend on the aspect ratio and the inflow Froude number. In contrast, for a wide channel the shock waves do not cross upstream of the first wave crest, and the flow conditions of undular jumps are independent of the aspect ratio. The flow conditions of undular jumps are classified by considering the cross position of the lateral shock waves and the inflow Froude number. Also, the hydraulic conditions for the formation of nonbreaking and breaking undular jumps are determined. The effect of the Reynolds number on undular-jump formations is discussed, and changes of the flow conditions with the Reynolds number are described.     

Acute myelogenous leukemia with monosomy 7, inv(3) (q21q26), involving activated EVI 1 gene occurring after a complete remission of lymphoblastic lymphoma: a case report

A 42-year-old female with a mediastinal tumor and massive pleural effusion ws admitted to our hospital in June 1993. Biopsy revealed lymphoblastic lymphoma. She had no evidence of distant metastasis except pleural effusion. Bone marrow examination revealed a normal karyotype (46, XY). The patient had been progression-free for more than 1 year after achieving complete remission by induction, consolidation and maintenance therapy according to the standard chemotherapy and involved-field radiation for lymphoblastic lymphoma. From May 1996 progressive leukopenia and thrombocytopenia developed. The diagnosis of refractory anemia with excess of blasts (RAEB) was made. Subsequently, in November 1996, she developed acute myelogenous leukemia (AML), M4 type by FAB classification. The karyotype of MDS and AML clones involved inversion (3) (q21q26) and monosomy 7. The EVI 1 gene was examined and was proved to be rearranged and activated. This may be the first case among the therapy-related cases of MDS/AML reported whose karyotypes were followed and in which the mRNA expression of EVI 1 gene involved was directly proved in the leukemogenesis process of chemotherapy-induced secondary MDS and AML.     

Random mutagenesis into the conserved Gly154 of subtilisin E: isolation and characterization of the revertant enzymes

We analyzed the role played by the conserved Gly154, a constituent of the P1 substrate-binding pocket of Bacillus subtilis subtilisin E, in the catalytic properties of the protease. Using an Escherichia coli expression system, the termination codon at position 154 in subtilisin E was first introduced to abolish the catalytic activity through truncation of the C-terminus from amino acid residues 154-275. We then attempted to obtain revertants with substitutions of various amino acids at position 154 by the polymerase chain reaction using a mixture of oligonucleotides. In addition to the Gly residue (wild-type), six amino acid substitutions (Ala, Arg, Leu, Phe, Pro and Thr) gave caseinolytic activity. When assayed with synthetic peptide substrates, most of the revertants showed a considerable decrease in specific activity and a P1 specificity similar to that of the wild-type enzyme. An Ala154 mutant purified from the periplasmic space in E. coli, however, resulted in an up to 2.3-fold preference for Val rather than Pro as a P2 substrate relative to the wild-type. Further, a significant 2-10-fold increase in the catalytic efficiency occurred in the Gly127Ala plus Gly154Ala combination variant, relative to the single Gly127Ala variant, without any change in the restricted specificity. The kinetic data and molecular modeling analysis demonstrate the important role of position 154 in the catalytic efficiency as well as in the substrate specificity of subtilisin E.     

Novel sub-100 nm surface chemical modification by optical near-field induced photocatalytic reaction

The surface modification is indispensable to facilitate new functional applications of micro/nanofluidics devices. Among many modification techniques developed so far, the photo-induced chemical modification is the most versatile method in terms of robustness, process simplicity, and feasibility of chemical functionality. In particular, the method is useful for closed spaces, such as post-bonded devices. However, the limitation by optical diffraction limit is still a challenging issue in scaling down the pattern sizes to nanoscale. Here, we demonstrated a novel surface modification on sub-100 nm scale utilizing the novel optical near-field (ONF) generated on nanostructures of photocatalyst (TiO₂). The minimum pattern size of 40 nm, which was much smaller than diffraction limit, was achieved using a visible light source (488 nm) and a conventional irradiation setup. The controllability of pattern size by light intensity, the feasibility of functionality, and the non-contact working mode have impacts on surface patterning of post-bonded micro/nanofluidics devices. It is also worthy to note that our results verified for the first time the ONF on nanostructures of non-metal materials and its ability to manipulate the chemical reaction on nanoscale.     

Removal of lead compounds from polyvinylchloride in electric wires and cables using cation-exchange resin

Recycling treatment of cable insulation resin generated from electric wires and cables was investigated. Conventional insulation PVC contains a lead component, tribase, as a thermal stabilizer and lead removal is necessary to recycle this PVC as insulation resin. This paper describes a solid surface adsorption method using ion exchange resin to remove the fine lead containing particles from PVC dissolved solution. Low lead concentration in the recovered PVC, complying with the requirements of RoHS, was achieved.     

Percolative behavior of transient photoconductivity in metal-free phthalocyanine nanocrystals

Transient photoconductivity in metal-free phthalocyanine (H₂Pc) nanocrystals dispersed in a polyester matrix is investigated. The H₂Pc nanocrystals concentration dependence of transient photoconductivity is examined above the percolation threshold at different temperatures. It is found that the disorder parameter is independent of temperature and increases with concentration of H₂Pc nanocrystals. These findings can successfully be explained by percolative behavior of photocarriers on geometric fractals.     

Deducing structural variations of the apex of probes used in near-field optical microscopy through simultaneous measurement of shear force and evanescent intensity

We propose a simple method employing the simultaneous detection of evanescent intensity and shear force to deduce variations in the near-field optical morphology of the apex of the probes used in near-field microscopy. Fabrication of our probes involves sharpening by chemical etching, metal coating, and removal of metal from the apex. We show that through the simultaneous measurement of shear force and evanescent intensity, it is possible to detect variations in the optical morphology of the very apex of the probes during near-field imaging by a scanning near-field optical microscope.     

A mathematical model for computer simulation of the direct continuous esterification process between terephthalic acid and ethylene glycol. Part II: Reaction rate constants

It has been confirmed that the reaction model proposed previously, which can express simultaneously the oligomer properties and the distillate properties under low esterification pressure, is applicable to a continuous direct esterification process in a practical plant. The experimental data of the first esterification reactor (RA-1) was obtained under low reaction pressures (atomospheric or 1 kg/cm²G) with the pilot plant throughput based on poly(ethylene terephthalate) (PET) polymer production of about 50 kg/h. The Arrhenius' parameters, frequency factor, and apparent activation energy, were determined fitting the experimental data of the pilot plant by using the Simplex method as an optimization technique. The activation energy of diethylene glycol (DEG) formation, E₇, is about twice as much as those of the esterifications, E₁, E₂, E₃, and E₄. The activation energies are E₁, = 19640 cal/mol, E₂ = 18140, E₃ = 22310, E₄ = 18380, E₅ = 2810, E₆ = 14960, and E₇ = 42520 cal/mol. Good agreement was obtained between experimental data and calculated predictions for several oligomer and distillate properties. The vapor-liquid equilibrium can be expressed by Raoult's law with little problem of practical use.