New idea of a small-sized neutron detector with a plastic fibre

A small-sized thermal neutron detector based on a (6)Li-glass scintillator and a plastic optical fibre has been developed for precise measurement of the spatial distribution of thermal neutron fluence rate. This detector was tested in experiments performed using thermal neutrons. The detector is useful in a thermal neutron field. However, the gamma-ray discrimination ability of the (6)Li-glass scintillator is not good in a low-intensity thermal neutron field. A new idea using a gamma-ray suppression method is proposed to reduce the uncertainty in the neutron counts due to the gamma-ray background. A novel small-sized thermal neutron detector consists of a (6)Li-glass scintillator, a hollow CsI(Tl) scintillator and plastic optical fibres. The evaluation of the gamma-ray suppression ability of the detector using the EGS4 code indicates that the gamma-ray suppression is effective.     

Feasibility study on using imaging plates to estimate thermal neutron fluence in neutron-gamma mixed fields

In current radiotherapy, neutrons are produced in a photonuclear reaction when incident photon energy is higher than the threshold. In the present study, a method of discriminating the neutron component was investigated using an imaging plate (IP) in the neutron-gamma-ray mixed field. Two types of IP were used: a conventional IP for beta- and gamma rays, and an IP doped with Gd for detecting neutrons. IPs were irradiated in the mixed field, and the photo-stimulated luminescence (PSL) intensity of the thermal neutron component was discriminated using an expression proposed herein. The PSL intensity of the thermal neutron component was proportional to thermal neutron fluence. When additional irradiation of photons was added to constant neutron irradiation, the PSL intensity of the thermal neutron component was not affected. The uncertainty of PSL intensities was approximately 11.4 %. This method provides a simple and effective means of discriminating the neutron component in a mixed field.     

Top-down process based on electrospinning, twisting, and heating for producing one-dimensional carbon nanotube assembly

Multiwalled carbon nanotube (MWNT)/poly(vinyl butyral) (PVB) composite nanofibers were prepared by electrospinning, successive twisting and heat treatment. The MWNTs were highly oriented in an electrified thin jet during electrospinning. The heat treatment of the twisted electrospun nanofiber yarns produced the characteristics of the CNT in the composite nanofiber yarns and enhanced their electrical properties, mechanical properties, and thermal properties. The electrical conductivity of the heated yarn was significantly enhanced and showed the maximum value of 154 S cm(-1) for the yarn heated at 400 °C. It is an order of magnitude higher than other electrospun CNT composite materials. These results demonstrated that the novel top-down process based on electrospinning, twisting, and heat treatment provide a promising option for simple and large-scale manufacture of CNT assemblies.     

Numerical study on flash‐boiling spray of multicomponent fuel

Flash‐boiling occurs when a fuel is injected into a combustion chamber where the ambient pressure is lower than the saturation pressure of the fuel. It has been known that flashing is a favorable mechanism for atomizing liquid fuels. On the other hand, alternative fuels, such as gaseous fuels and oxygenated fuels, are used to achieve low exhaust emissions in recent years. In general, most of these alternative fuels have high volatility and flash‐boiling takes place easily in the fuel spray when injected into the combustion chamber of an internal combustion engine under high pressure. In addition the multicomponent mixture of high‐ and low‐volatility fuels has been proposed in the previous study in order to control the spray and combustion processes in an internal combustion engine. It was found that the multicomponent fuel produces flash‐boiling with an increase in the initial fuel temperature. Therefore, it is important to investigate these flash‐boiling processes in fuel spray. In the present study, the submodels of a flash‐boiling spray are constructed. These submodels consider the bubble nucleation, growth, and disruption in the nozzle orifice and injected fuel droplets. The model is implemented in KIVA3V and the spray characteristics of multicomponent fuel with and without flashing are numerically investigated. In addition, these numerical results are compared with experimental data obtained in the previous study using a constant volume vessel. The flashing spray characteristics from numerical simulation qualitatively show good agreement with the experimental results. In particular, it is confirmed from both the numerical and experimental data that flash‐boiling effectively accelerates the atomization and vaporization of fuel droplets. This means that a lean homogeneous mixture can be quickly formed using flash‐boiling in the combustion chamber. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(5): 369–385, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20117     

Studies on the interaction between lanthanide ions and ligands, in solid complexes of lanthanide hexacyanometalates. Part II. The kinetics of thermal dehydration of lanthanide hexacyanocobaltate (III) hydrates, Ln[Co(CN)6]·nH2O and yttrium hexacyanocobaltate (III) tetrahydrates

Series complexes of lanthanide hexacyanocobaltates (III), Ln[Co(CN)₆]·nH₂O (Ln=lanthanide ions; n=5,4) and yttrium hexacyanocobaltates (III) tetrahydrate were prepared, and the kinetics of the thermal dehydrations of these hydrates was studied. The dehydrations of Ln[Co(CN)₆]·5H₂O (Ln=La to Nd) took place through at least three stages, and those of Ln[Co(CN)₆]·4H₂O (Ln=Ce to Lu, and Y) through at least two stages. The each dehydration stage was found to be described as a first order reaction, F₁. Activation energy for each stage was determined on the basis of thermogravimetry. The relationship between the activation energy for the each dehydration stages and the thermal stability of the series hydrates which was changing with the decrease of the ionic radii of lanthanide ions, was discussed.     

Interactions between dyes and surfactants in inkjet ink used for textiles

Optimal preparation of inkjet ink should be possible through the elucidation of the relationship between dye/additive interactions and ink performance. In the present study, the interactions between the dyes and surfactant additives were investigated. To investigate the physical properties of the surfactants used, the critical micelle concentration (cmc) and the aggregation number (N) were determined using electron spin resonance, static light-scattering, and fluorescence spectroscopy. On the basis of the cmc and N values, the visible absorption spectra of aqueous acid dye solutions (C. I. Acid Red 88, 13, and 27) containing surfactants (i.e., Surfynol 465 (S465), octaethylene glycol monododecyl ether (OGDE), and sodium dodecyl sulfate (SDS)) were measured. From the dependence of the spectra on the surfactant concentration, the binding constants, K(bind), of the acid dyes with the surfactant micelles were calculated: the K(bind) values decreased in the order of C. I. Acid Red 88 > C. I. Acid Red 13 > C. I. Acid Red 27, which correlates with the number of sulfonate groups. For all the dyes, the K(bind) values with the nonionic surfactants, S465 and OGDE, were much larger than those with the anionic surfactant, SDS. The thermodynamic parameters of the binding, i.e., the enthalpy change, ΔH(bind), and entropy change, ΔS(bind), were determined via the temperature dependence of the binding constants. The positive ΔH(bind) value for S465 indicates an endothermic binding process, while the negative ΔH(bind) values for SDS and OGDE indicate exothermic binding processes.     

Synthesis and photoluminescence of a novel Sr-SiAlON:Eu blue-green phosphor (Sr14Si68−sAl6+sOsN106−s:Eu (s ≈ 7))

A novel Eu²⁺ activated Sr-SiAlON oxynitride phosphor, with the chemical composition of Sr₁₄Si_68−sAl_6+sO_sN_106−s:Eu²⁺ (s ≈ 7), was synthesized by firing the powder mixture of SrO, SrSi₂, α-Si₃N₄, AlN and Eu₂O₃ at 1900 °C for 6 h under 1 MPa nitrogen atmosphere. The structure has a typical feature of SiAlON consisting of the host framework which is constructed by a three-dimensional MX₄ tetrahedral (M: Si or Al; X: O or N) network, and Sr or Eu²⁺ ions as the guest ions. It has been shown that the Sr-SiAlON:Eu²⁺ phosphor has the excitation band covering the range of the ultraviolet light region to 500 nm, and exhibits an intense blue-green color with the emission band centered at about 508 nm. The temperature dependent emission intensity of the Sr-SiAlON:Eu²⁺ phosphor is better than that of a typical blue-green Ba₂SiO₄:Eu²⁺ phosphor. It is demonstrated that Sr-SiAlON:Eu²⁺ phosphor is very promising for use in white -LEDs.     

Functional characteristics and membrane localization of rat multispecific organic cation transporters, OCT1 and OCT2, mediating tubular secretion of cationic drugs

We have isolated a kidney-specific organic cation transporter, rat OCT2, which is distinct from rat OCT1 (Okuda M, Saito H, Urakami Y, Takano M and Inui K (1996) Biochem Biophys Res Commun 224:500-507). In our study, the functional characteristics and membrane localization of OCT1 and OCT2 were investigated by uptake studies using MDCK cells transfected with rat OCT1 or OCT2 cDNA (MDCK-OCT1 or MDCK-OCT2) and immunological studies. Tetraethylammonium (TEA) uptake by both MDCK-OCT1 and MDCK-OCT2 cells was markedly elevated when TEA was added to the basolateral medium, but not to the apical medium. Efflux of TEA from MDCK-OCT1 and MDCK-OCT2 cells was not changed by extracellular pH from 5.4 to 8.4, whereas TEA uptake by both transfectants was decreased by acidification of extracellular medium. Apparent Km values for TEA uptake by MDCK-OCT1 and MDCK-OCT2 cells were 38 and 45 microM, respectively. Although various hydrophilic organic cations such as 1-methyl-4-phenylpyridinium, cimetidine, quinidine, nicotine, N1-methylnicotinamide and guanidine markedly inhibited TEA uptake by both MDCK-OCT1 and MDCK-OCT2 cells, there were no significant differences in the apparent inhibition constants (Ki) against these organic cations between both transfectants. Furthermore, immunological studies using a polyclonal antibody against OCT1 revealed that OCT1 was expressed in the basolateral membranes but not in the brush-border membranes of the rat kidney. These results suggested that both OCT1 and OCT2 are basolateral-type organic cation transporters with broad substrate specificities, mediating tubular secretion of cationic drugs.     

Numerical modelling of the growth of sulfate-reducing bacteria indigenous to an oilfield in Japan

Abstract

We performed kinetic studies of the growth of sulfate-reducing bacteria (SRB) indigenous to the water in an oilfield in Japan. The SRB growth was most active in injection water supplemented with ethanol; therefore, the SRB inhabiting the injection water of the reservoir were assumed to grow predominantly by assimilating sulfate and ethanol and generating H₂S. Based on this mechanism and the results of incubation experiments in the injection water, we derived numerical models that calculate the growth rate and H₂S generation of the SRB under three variables (temperature, sulfate concentration, and ethanol concentration).     

Fluctuation in energy-loss measurements in allene-doped liquid argon for heavy ions

Liquid argon (LAr) has suitable properties for use as a particle-detector medium, however, its response to heavy ions is not linear, because of the non-perfect collection of charge produced by the incident ions due to the strong recombination between the liberated electrons and argon ions. We were able to improve the linearity of the response by doping photoionization materials, such as allene (C₃H₄), to LAr. Using allene-doped LAr, we made some experiments of the heavy ion calorimeters for the mass identification of relativistic iron ions, but this approach was unsuccessful. We therefore investigated the cause of the failure using relativistic heavy ions of neon, argon and iron. The energy resolutions obtained experimentally were of the order of several percent at the full width at half maximum (FWHM) for neon to iron ions passing through a LAr gap of 10 mm. These values were 2 or 3 times worse than those predicted theoretically, and the poor energy resolution led to insufficient mass resolution. Here, we describe methods for measuring fluctuation in energy-loss signals in LAr, and discuss the factors determining the resolution.