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951.
A phoswitch-type detector has been developed for monitoring neutron doses in high-energy accelerator facilities. The detector is composed of a liquid organic scintillator (BC501A) coupled with ZnS(Ag) sheets doped with 6Li. The dose from neutrons with energies above 1 MeV is evaluated from the light output spectrum of the BC501A by applying the G-function, which relates the spectrum to the neutron dose directly. The dose from lower energy neutrons, on the other hand, is estimated from the number of scintillations emitted from the ZnS(Ag) sheets. Characteristics of the phoswitch-type detector were studied experimentally in some neutron fields. It was found from the experiments that the detector has an excellent property of pulse-shape discrimination between the scintillations of BC501A and the ZnS(Ag) sheets. The experimental results also indicate that the detector is capable of reproducing doses from thermal neutrons as well as neutrons with energies from one to several tens of megaelectronvolts (MeV). 相似文献
952.
Separation of long DNA molecules by quartz nanopillar chips under a direct current electric field 总被引:1,自引:0,他引:1
Kaji N Tezuka Y Takamura Y Ueda M Nishimoto T Nakanishi H Horiike Y Baba Y 《Analytical chemistry》2004,76(1):15-22
We have established the nanofabrication technique for constructing nanopillars with high aspect ratio (100-500 nm diameter and 500-5000 nm tall) inside a microchannel on a quartz chip. The size of pillars and the spacing between pillars are designed as a DNA sieving matrix for optimal analysis of large DNA fragments over a few kilobase pairs (kbp). A chip with nanopillar channel and simple cross injector was developed based on the optimal design and applied to the separation of DNA fragments (1-38 kbp) and large DNA fragments (lambda DNA, 48.5 kbp; T4 DNA, 165.6 kbp) that are difficult to separate on conventional gel electrophoresis and capillary electrophoresis without a pulsed-field technique. DNA fragments ranging from 1 to 38 kbp were separated as clear bands, and furthermore, the mixture of lambda DNA and T4 DNA was successfully separated by a 380-microm-long nanopillar channel within only 10 s even under a direct current (dc) electric field. Theoretical plate number N of the channel (380-1450 microm long) was 1000-3000 (0.7 x 10(6)-2.1 x 10(6) plates/m). A single DNA molecule observation during electrophoresis in a nanopillar channel revealed that the optimal nanopillars induced T4 DNA to form a narrow U-shaped conformation during electrophoresis whereas lambda DNA kept a rather spherical conformation. We demonstrated that, even under a dc electric field, the optimal nanopillar dimensions depend on a gyration radius of DNA molecule that made it possible to separate large DNA fragments in a short time. 相似文献
953.
An analytical technique to measure reactions in biological membranes was developed and applied to monitoring the hydrolysis reaction of phospholipids (dipalmitoylphosphatidylcholine, DPPC) by phospholipase A(2). The technique uses the time-resolved quasi-elastic laser scattering (TR-QELS) method to measure an oil/phospholipid monolayer/water membrane system by monitoring the change of interfacial tension under a noncontact condition and in real time. When the TR-QELS method is used with the newly developed oil/phospholipid monolayer/water membrane system, measurement of the hydrolysis reaction of phospholipids with long alkyl chains (C >or=16), which are the major components in biological membranes, becomes possible. The reaction progress is monitored by the increase of interfacial tension at the oil/water interface caused by the decrease of surface-active DPPC molecules due to the reaction. The characteristic phases, namely, lag, burst, and equilibrium, are observed. The relationship between the duration of the lag phase (the rate-limiting step of the reaction) and the concentration of calcium ion (an essential cofactor of the reaction) is also investigated. Increase of calcium ion concentration in the subphase is found to shorten the duration of the lag phase. In addition, the real-time measurement simplifies the estimation process for the reaction activation energy. 相似文献
954.
Takeo Hyodo Katsuhiko Maeda Takahiro Ito Kazuhiro Sasahara Yasuhiro Shimizu Makoto Egashira 《Journal of Electroceramics》2004,13(1-3):519-524
Effects of fabrication conditions on the microstructure of thick BaTiO3 films have been investigated by employing slide-off transfer printing technique. Formation of dense films with good adhesive properties was difficult when screen-printing was employed in preparing the slide-off transfer sheets (BaTiO3 green films), irrespective of the kind of solvents used for the slurries. On the other hand, relatively dense films could be fabricated from the slide-off transfer sheet prepared by spin-coating of the slurries consisting of fine BaTiO3 powder (particle size: ca. 0.1 m), printing oil, and 2-propanol, though cracks formed obviously. Co-addition of large BaTiO3 particles (particle size: ca. 0.5 m) was very effective for reducing the formation of cracks, and homogenous and dense films could be fabricated by controlling the additive amount of the large particles. 相似文献
955.
Chie Inui Hiroaki Kura Tetsuya Sato Yosuke Tsuge Seimei Shiratori Hisanori Ohkita Akihiro Tagaya Yasuhiro Koike 《Journal of Materials Science》2007,42(19):8144-8149
Surface-modified ZnTe nanoparticles were mixed in a zero-birefringence polymer matrix. Transmission electron microscopy images
revealed that aggregates of ZnTe nanoparticles with a diameter of ∼20 nm were uniformly dispersed in the polymer. The transmittance
of ZnTe nanocomposites rapidly decreased at wavelengths shorter than the critical wavelength corresponding to the band gap
of ZnTe nanoparticles, an effect which became significant as the volume fraction of particles increased. In this way, the
optical characteristic of ZnTe nanoparticles was added to the polymer. The intrinsic zero-birefringence was confirmed in the
heat-drawn ZnTe nanocomposites. As the ZnTe nanocomposites were left in air, a lowering of transmittance was observed. This
was due to the oxidation of Zn and the resultant deposition of Te in the ZnTe nanocomposite, as the light absorption of Te
is significant. The formation of oxygen non-permeable SiO2 films onto the ZnTe nanocomposite by the sol-gel method was useful in preventing oxidation so that the decrement of transmittance
decreased from 47.2% to 14.9% at 530 nm near the ZnTe band gap. 相似文献
956.
Yasuhiro Iwasaki Shinji Minamisawa Hirofumi Takikawa Tateki Sakakibara Hiroshi Hasegawa 《Vacuum》2006,80(11-12):1266
Diamond-like carbon (DLC) films were deposited by a T-shape filtered arc deposition (T-FAD) apparatus, applying bias voltage to the plasma transportation duct which filters the macrodroplet emitted from the cathode, in order to obtain a higher deposition rate. Ion current, deposition rate, discharge voltage, duct current, and anode current were measured as a function of duct bias. The anode current decreased and the duct current increased when a positive bias was applied to the duct. This fact indicates that the T-shape duct acted as another anode of the vacuum arc discharge. It was found that the maximum deposition rate as well as the ion current was obtained at about 15 V of duct bias. Improvement in plasma transportation to the process chamber through the duct was considered from the viewpoint of the characteristics of duct current against bias voltage. The value of the optimum duct bias was the same as the intersection point of the characteristics of duct current against bias voltage. 相似文献
957.
Masuda T Arai R Komatsubara O Tako Y Harashima E Nitta K 《Habitation (Elmsford, N.Y.)》2005,10(2):87-97
Productivities of 29 crops in the Closed Ecology Experiment Facilities (CEEF) were measured. Rice and soybean showed higher productivities than these given by the Advanced Life Support System Modeling and Analysis Project Baseline Values and Assumption Document (BVAD), but productivities of some other crops, such as potato and sweet potato, were lower. The cultivation data were utilized to develop a 1-week cycle menu for Closed Habitation Experiment. The menu met most of the nutritional requirements. Necessary cultivation area per crew was estimated to be 255 m2. Results from this study can be used to help design the future Advanced Life Support System (ALSS) including the CEEF. 相似文献
958.
Nakamura C Inuyama Y Goto H Obataya I Kaneko N Nakamura N Santo N Miyake J 《Analytical chemistry》2005,77(23):7750-7757
The purpose of this study is to develop a dioxin detection method using a short peptide alternative to an immunoantibody. A full peptide library consisting of 2.5 million possible amino acid combinations was constructed by a solid-phase split synthesis approach using 19 natural amino acids. The peptide beads were subjected to a competitive binding assay between 2,3,7-trichlorodibenzo-p-dioxin and N-NBD-3-(3',4'-dichlorophenoxy)-1-propylamine (NBD-DCPPA) in a buffer containing 20% 1,4-dioxane. Two almost identical pentapeptides, FLDQI and FLDQV, that could bind dioxin were screened from the combinatorial library. NBD-DCPPA and the peptide synthesized on resin beads could be utilized to determine dioxin concentrations. The fluorescence intensity of the beads was measured using fluorescence microscopy to make a calibration curve for the dioxin concentrations. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (2,3,7,8-TeCDD) could also detected in the presence of 30% 1,4-dioxane. To optimize the peptide sequence, a one-amino acid-substituted library was prepared using amino acids including nonnatural amino acids. The internal amino acids, LDQ, could not be substituted by any other amino acids. This result indicates that these three side chains are essential to recognize dioxins. The peptide C terminus substituted by phenylglycine showed a 10 times lower detection limit of 2,3,7,8-TeCDD of 150 pM (50 pg/mL) than the original sequence FLDQV. The cross reactivity of the dioxin binding peptides including the secondary derivatives was investigated. Some polycyclic aromatic hydrocarbons bound to the peptide beads, but nonchlorinated dibenzo-p-dioxin and PCB did not. From these results, we demonstrate the potential of short peptides as a practical sensor material targeting low molecular weight compounds such as dioxin. 相似文献
959.
A method for the simultaneous retrieval of gas concentrations and an extinction spectrum of aerosols and polar stratospheric clouds from infrared transmission spectra observed in the solar occultation geometry is described. It is particularly suited to measurements by Fourier-transform spectrometers with relatively low spectral resolution (0.1-1 cm(-1)). The method does not require a priori assumptions on aerosol properties; it utilizes only the fact that the wave-number dependence of aerosol extinction is much weaker than that of gas absorption. In this method, an aerosol extinction spectrum is approximated by a straight line within a relatively wide spectral range defined as mediumwindow. 相似文献
960.
Yasuhiro?NakajimaEmail author Shigehiro?Ishizuka Haruo?Tsuruta Anas?Iswandi Daniel?Murdiyarso 《Nutrient Cycling in Agroecosystems》2005,71(1):33-42
The most probable number (MPN) method and dicyandiamide (DCD), an autotroph-specific inhibitor, were used to identify microbial processes that produced N2O in acid soils. Nitrous oxide production was investigated in six sites in four different land-use patterns at Pasirmayang in Jambi province, in Sumatra, Indonesia, using soils collected in October 1999, March 2000 and June 2000. The six sites were primary forests (P1 and P2), loggedover forests (L2), a young rubber plantation established after forest had been logged and burned in March 1998 (L1), a plantation of Gmelina arborea established after logging and burning of forest in August 1996 (O), and a rubber plantation of a small landholder established in 1993 (R). Very small numbers of autotrophic ammonia oxidizers and autotrophic nitrite oxidizers were detected. Heterotrophic nitrifiers were detected at all sites, with the highest MPNs at L1 and L2. In incubation experiments, the emission of N2O from soils increased at all six sites after adding citrate, a substrate for heterotrophic nitrifiers. No correlation appeared between denitrification activity and N2O flux. We conclude that heterotrophic nitrifiers are the main microbial contributors to N2O emission from acid soils in Pasirmayang, Jambi. 相似文献