Modelling and optimal control of oversaturated transportation networks

This paper treats an optimal control problem of automobile traffic flows in an oversaturated transportation network with a rectangular grid of intersections. All O-D (origin-destination) traffic flows are divided into portions at each origin and one route for travelling to the destination is assigned to the each portion. The traffic flows are controlled by the traffic signals placed at each intersection. Examples of numerical solutions, which are obtained by applying the linear-programming technique, are presented. The effect of route assignment for decreasing the traffic congestion is shown by the examples.     

Recent aspect of substoichiometry in trace analysis

A review of the substoichiometry in trace analysis is presented. Recent new developments and practical applications are described.     

Novel thermal curing reaction of oxetane resins with polyfunctional phenols

The thermal curing reaction of polyfunctional oxetanes (oxetane resins) such as tris[4‐(3‐ethyloxetane‐3‐yl)methoxyphenyl]methane (TEOMP) and 1,3,5‐tris(3‐ethyl‐3‐oxetanylmethoxy)benzene with certain polyfunctional phenols was performed in bulk with quaternary onium salts as catalysts. The reaction proceeded smoothly at 180–220 °C and produced insoluble gel products, and the rate of gel production increased with the reaction temperature. The rate of the addition reaction of TEOMP with 3,3′,5,5′‐tetrachlorobisphenol A was also measured by IR spectroscopy, and the rate of reaction was proportional to the product of the oxetane concentration and the catalyst concentration in the film state. Furthermore, the glass‐transition temperatures and 5 and 10 wt % weight‐loss temperatures of the resulting gel products were confirmed with differential scanning calorimetry and thermogravimetric analysis, and the glass‐transition temperatures and 5 wt % weight‐loss temperatures were 127–162 °C and 323–351 °C, respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2028–2037, 2005     

A biochemical sniffer-chip for convenient analysis of gaseous formaldehyde from timber materials

A biochemical gas-sensor (sniffer-chip) with formaldehyde dehydrogenase (FALDH) was developed for convenient analysis of gaseous formaldehyde with high gas-selectivity. The sniffer-chip for formaldehyde in the gas phase was constructed by immobilizing FALDH to a Pt-electrode coated hydrophilic PTFE membrane. The oxidation current of NADH produced by the enzymatic reactions was measured by amperometric analysis. The calibration range of the sniffer-chip for formaldehyde in the gas phase was from 40 to 2000 ppb, which encountered the maximum permissible concentration of formaldehyde vapor in the residential house (80 ppb) and formaldehyde detection limit for the human sense of smell (410 ppb). As the resident-environmental application, the sniffer-chip was possible to measure the formaldehyde concentration from some timber materials (3 kinds of interior timber and 2 kinds of exterior formwork timber) within 3 min. The calculated concentration value by a regression analysis was consistent with those of a commercially available gas sensor and a gas detector tube for formaldehyde. The FALDH sniffer-tip would be effective and convenient approach to detect and measure gaseous formaldehyde with high gas-selectivity at the residential atmosphere. Correspondence: Kohji Mitsubayashi, Department of Biomedical Devices and Instrumentation, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-0062, Japan     

Electrochemical sensor with flavin-containing monooxygenase for triethylamine solution

A bioelectronic sensor for triethylamine (TEA) was developed with a flavin-containing monooxygenase type 3 (FMO-3). The TEA biosensor consisted of a Clark-type dissolved-oxygen electrode and an FMO-3 immobilized membrane. The FMO-3 solution was mixed with a poly(vinyl alcohol) containing stilbazolium groups (PVA-SbQ), coated on to the dialysis membrane, and the membrane was irradiated with a fluorescent light to immobilize the enzyme. In order to amplify the biosensor output, a substrate regeneration cycle, obtained by coupling the monooxygenase with l-ascorbic acid (AsA) as reducing reagent system, was applied. The effect of pH on the determination of TEA was studied. The maximum response was achieved at pH >9.0. A drop of the phosphate buffer solution with the AsA was put on the sensing area of the oxygen electrode, and the FMO-3 immobilized membrane was placed on the oxygen electrode and covered with a supporting Nylon mesh net which was secured with a silicone O-ring. A measurement system for TEA solution was constructed using the FMO-3 biosensor, a personal computer, a computer-controlled potentiostat, and an A/D converter. The FMO-3 biosensor was used to measure TEA solution from 0.5 to 4.0 mmol L⁻¹ with 10.0 mmol L⁻¹ AsA. The biosensor also had good reproducibility, for example a 6.31% coefficient of variation for five measurements, and the output current was maintained over a few hours. In order to improve the selectivity of the TEA biosensor, three type of biosensor with FMO isomer types 1, 3, and 5 were constructed and used to measure nitrogen and sulfur compounds. The outputs of the isomer biosensors indicated individual patterns for each sample solution. The selectivity of TEA biosensor would be improved, and determination of sulfur and nitrogen compounds would be possible, by using the different output of biosensors prepared from different FMO isomers.     

Induced smectic phase in mixtures of hyperbranched polyester and liquid crystal mesogens

The phase diagram of a mixture consisting of hyperbranched polyester (HBPEAc-COOH) and eutectic nematic liquid crystals (E7) has been established experimentally by means of differential scanning calorimetry and polarized optical microscopy subjected to prolonged annealing. The observed phase diagram is an upper azeotrope, exhibiting the coexistence of nematic + isotropic phase in the vicinity of 90 approximately 110 degrees C above the clearing temperature of neat E7 (60 degrees C). With decreasing temperature, a focal-conic fan shaped texture develops in the composition range of 63 approximately 93 wt % of the annealed E7/HBPEAc-COOH blends, suggestive of induced smectic phase in the mixture. Wide angle X-ray diffraction (WAXD) technique revealed the existence of higher order mesophase(s).     

Characterization and mechanistic study of a radical SAM dehydrogenase in the biosynthesis of butirosin

BtrN encoded in the butirosin biosynthetic gene cluster possesses a CXXXCXXC motif conserved within the radical S-adenosyl methionine (SAM) superfamily. Its gene disruption in the butirosin producer Bacillus circulans caused the interruption of the biosynthetic pathway between 2-deoxy-scyllo-inosamine (DOIA) and 2-deoxystreptamine (DOS). Further, in vitro assay of the overexpressed enzyme revealed that BtrN catalyzed the oxidation of DOIA under the strictly anaerobic conditions along with consumption of an equimolar amount of SAM to produce 5'-deoxyadenosine, methionine, and 3-amino-2,3-dideoxy-scyllo-inosose (amino-DOI). Kinetic analysis showed substrate inhibition by DOIA but not by SAM, which suggests that the reaction is the Ordered Bi Ter mechanism and that SAM is the first substrate and DOIA is the second. The BtrN reaction with [3-2H]DOIA generated nonlabeled, monodeuterated and dideuterated 5'-deoxyadenosines, while no deuterium was incorporated by incubation of nonlabeled DOIA in the deuterium oxide buffer. These results indicated that the hydrogen atom at C-3 of DOIA was directly transferred to 5'-deoxyadenosine to give the radical intermediate of DOIA. Generation of nonlabeled and dideuterated 5'-deoxyadenosines proved the reversibility of the hydrogen abstraction step. The present study suggests that BtrN is an unusual radical SAM dehydrogenase catalyzing the oxidation of the hydroxyl group by a radical mechanism. This is the first report of the mechanistic study on the oxidation of a hydroxyl group by a radical SAM enzyme.     

Determination of uranium by neutron activation analysis using substoichiometric separation

Three analytical methods for uranium by neutron activation are described. The methods are based on the substoichiometric separation of barium or lanthanum, which are the fission products of uranium-235 by neutron irradiation. Uranium contents in high purity materials were determined by the methods, which were found to be useful for the determination of a trace amounts of uranium.     

Determination of trace elements in semiconductor materials by neutron activation analysis using the radioisotope addition technique

The determination of trace elements in highly activated matrix components was carried out by neutron activation analysis using the radioisotope addition technique. The method is based on the addition to the irradiated test sample of a radioisotope which is a diffeent nuclide of the element to be determined. After separation, the chemical yield is calculated from the radioactivity added and the element is determined by an ordinary technique. Twelve elements in indium phosphide and eight elements in gallium arsenide could be determined by the method.