Reproducible fabrication of a fiber probe with a nanometric protrusion for near-field optics

We propose a new type of fiber probe with a nanometric protruding tip emerging from a metal film and describe a novel method, called the selective resin-coating method, for fabricating such probes. It is a reproducible etching process consisting of four steps and can be applied to silica fibers sharpened by selective chemical etching. With this method, we obtained tips with the apex diameter and the foot diameter of the protrusion being less than 10 and 30 nm, respectively, when the gold film was ~120 nm thick.     

An electrochemical study of the behaviour of ear piercing studs immersed in a culture medium

Two commercial studs, of gold-coated stainless steel and copper–zinc alloy, respectively, and a laboratory-made titanium stud were chosen for corrosion studies. Corrosion behaviour in a culture medium (CM) was studied using electrochemical impedance spectroscopy and polarization measurements, as a function of immersion time. The elements that leached out into the CM electrolyte were analysed by instrumental neutron activation analysis. Scanning electron microscopy and energy dispersive X-ray techniques were utilized in the analysis of the stud surfaces before and after their immersion in a CM solution. The cytotoxicity of the tested studs was also determined. The titanium stud showed the best combination of properties, high corrosion resistance and low cytotoxicity, while the gold-coated stainless steel stud occupied an intermediate position.     

Possible dual roles of an allelopathic compound,cis-dehydromatricaria ester

The aqueous extract of the root ofSolidago altissima was lethal to nematodes. The major compound isolated from the toxic fraction wascis-dehydromatricaria ester (methyl 2-decene-4,6,8-triynoate), which is already known as an allelopathic compound of a composite showing growth-inhibition to a rice seedling. This compound showed high toxicity to plant-parasite nematodes. A composite exudes one defending substance against both competitive plants and plant-parasite nematodes.Supported in part by The Ministry of Education, Science and Culture, Japan, Grant No. 00586036.     

Study on the supported Cu-based catalysts for the low-temperature water–gas shift reaction

This paper presents a study on the influence of support (Al₂O₃, MgO, SiO₂-Al₂O₃, SiO₂-MgO, β-zeolite, and CeO₂) of Cu-ZnO catalysts for the low-temperature water–gas shift reaction. Supported Cu-ZnO catalysts were prepared by the conventional impregnation method, followed by the H₂ reduction. The activity of Cu-ZnO catalysts for the water–gas shift (WGS) reaction was largely influenced by the kind of support; Cu-ZnO catalysts supported on Al₂O₃, MgO, and CeO₂ showed high activity, while those on SiO₂-Al₂O₃, SiO₂-MgO and β-zeolite showed less activity in the temperature range 423–523 K. XRD analysis demonstrated that the copper species were highly dispersed on the supports used in the present study, except for a MgO support. TPR results of a series of supported CuO-ZnO catalysts suggest that the reducibility of CuO is one of the important factors controlling the activity of the WGS reaction over the supported catalysts.     

Interdigital transducer generated surface acoustic waves suitable for powder transport

Recently, in the electronics and pharmaceutical industries, miniature devices that can transport a tiny amount of dry powder with a particle size of 100 μm or less are desired. We therefore focused on a surface acoustic wave (SAW) device, and we experimentally studied an interdigital transducer (IDT) that generates the SAW. As a result, it was found that an IDT with a 2-mm pitch size at a 90° inclination angle, against the perpendicular direction of a piezoelectric wafer (127.8° y-rotated x-propagating LiNbO₃) orientation flat, had a high efficiency of copper powder (about 100-μm particle size) transport. Then, to investigate the availability of a SAW actuator with this highly efficient IDT, we fabricated a miniature feeder (13-mm height × 18-mm width × 78-mm length) mounted with a hopper on the SAW actuator and carried out a powder supply experiment. As a result, it was found that, when 1 W of electric power was applied to the IDT of the feeder, the powder supply capability of the feeder was about 18 mg/s. From this fact, it was experimentally shown that a SAW actuator with a highly efficient IDT has a great potential to control dry powder with superior accuracy.     

Detection of pro- and anti-inflammatory cytokines in stools of patients with inflammatory bowel disease

Astroglial cells protect neurons against oxidative damage. The antioxidant glutathione plays a pivotal role in the neuroprotective action of astroglial cells which is impaired following loss of glutathione. Anethole dithiolethione (ADT), a sulfur-containing compound which is used in humans as a secretagogue, increases glutathione levels in cultured astroglial cells under "physiological" conditions and is thought thereby to protect against oxidative damage. Presently, we report the effect of ADT (3-100 microM) on glutathione content of and efflux from rat primary astroglia-rich cultures under "pathological" conditions, i.e., extended deprivation of glucose and amino acids. Although cellular viability was not affected significantly, starvation of these cultures for 24 h in a bicarbonate buffer lacking glucose and amino acids led to a decrease in glutathione and protein content of approximately 43% and 40%, respectively. Although no effect on the protein loss occurred, the presence of ADT during starvation counteracted the starvation-induced loss of intracellular glutathione in a concentration-dependent way. At a concentration of 100 microM ADT even a significant increase in astroglial glutathione content was noted after 24 h of starvation. Alike intracellular glutathione levels, the amount of glutathione found in the buffer was elevated substantially if ADT was present during starvation. This ADT-mediated, apparent increase in glutathione efflux was additive to the stimulatory effect on extracellular glutathione levels of acivicin (100 microM), an inhibitor of extracellular enzymatic glutathione breakdown. However, the ADT-induced elevation of both intra- and extracellular glutathione content during starvation was prevented completely by coincubation with buthionine sulfoximine (10 microM), an inhibitor of glutathione synthesis. These results demonstrate that, most likely through stimulation of glutathione synthesis, ADT enables astroglial cells to maintain higher intra- and extracellular levels of glutathione under adverse conditions. Considering the lowered glutathione levels in neurodegenerative syndromes, we conclude that further evaluation of the therapeutic potential of the compound is warranted.     

Effect of oxygen concentration on nitrogen removal by Nitrosomonas europaea and Paracoccus denitrificans immobilized within tubular polymeric gel

Tubular gel reactors containing Nitrosomonas europaea and Paracoccus denitrificans, which remove nitrogen from solutions through a process of nitrification and denitrification, require oxygen for ammonia oxidation, the first and rate-limiting step in the process. To accelerate ammonia oxidation, high concentrations of oxygen were applied to the reactors instead of air. Although a 50% O₂:N₂ gas mixture and pure oxygen were both toxic to free N. europaea cells, they actually accelerated ammonia oxidation by N. europaea immobilized within the tubular gel. Indeed, the rate of ammonia oxidation by a tube exposed to pure oxygen was twice that of one exposed to 20% O₂. When the distribution of N. europaea cells within the tubes was investigated using a fluorescently-labeled antibody, colonies were found on the external surface of the tube exposed to 20% O₂, but were located at a depth of 120–300 μm from the external surface in the case of the tube exposed to pure oxygen. The region between the external surface of the gel and the colonies apparently acted as a barrier, reducing the diffusion of oxygen and thus protecting the cells from oxygen cytotoxicity.     

Active control of jet premixed flames in a model combustor with manipulation of large-scale vortical structures and mixing

Active control of a bluff-body stabilized methane/air jet flame issued from a coaxial nozzle is made by using miniature magnetic flap actuators attached to the outer nozzle. CH radical chemiluminescence, and CO and NO_x emissions are measured to assess the flame characteristics. By changing the flapping Strouhal number, the flame stability and CO emission are drastically improved under different equivalence ratio (?) conditions. At ? = 0.72, the optimum Strouhal number for stable combustion is unity, since methane/air mixing is enhanced by large-scale vortices synchronized with the flap motion. On the other hand, at a lower equivalence ratio of ? = 0.48, the optimum Strouhal number is much larger than unity; with small-scale vortices, the premixed combustion is stabilized by stratified mixing. In addition to acetone and OH-PLIF, a new two-line OH-PLIF is employed for flame temperature measurement. The longitudinal flame temperature distribution is obtained from conditional-averaged OH fluorescence intensities at the OH front taken with two different excitation lines. CO and NO_x emission characteristics of the controlled flame are discussed on the basis of the local fuel and OH distributions and the flame temperature.     

Use of excess solid-phase capacity in immunoassays: advantages for semicontinuous, near-real-time measurements and for analysis of matrix effects

A flow-based immunoassay system using solid-phase particles with high binding capacity was used for semicontinuous, near-real-time, measurement of 17beta-estradiol (E2). The high binding capacity of the solid phase was exploited to enable (i) a quantitative determination of E2 concentration, based on rate of accumulation of fluorescently labeled anti-E2 antibody on the solid phase, and (ii) the use of a single solid phase for more than a dozen competitive binding measurements. The high binding capacity of the solid phase also permitted the immobilization of a second capture antigen. Biotin was immobilized as a second antigen and used to evaluate a biotin anti-biotin system as a control for matrix effects in the E2 immunoassay. In phosphate-buffered saline, E2 could be quantified (in the range of 10-1000 pM) by using either the summation or ratio of the signals from the labeled anti-E2 and anti-biotin antibody in the presence of biotin at a constant concentration. The same referencing system was applied to estimate the matrix effects in selected environmental samples. Matrix effects that inhibited the binding of the anti-E2 antibody to the solid phase led to false positive responses, but these matrix effects could be identified and partially corrected using the response from the anti-biotin antibody.     

In planta transformation of kenaf plants (Hibiscus cannabinus var. aokawa No. 3) by Agrobacterium tumefaciens

Kenaf was transformed by inoculation of Agrobacterium tumefaciens onto the meristems of young plants in pots. The transformation was demonstrated by three lines of evidence: a phenotypic inheritance from T(0) to T(1) plants, detection of the transgene in both T(0) and T(1) plants, and rescue of plasmids composed of T-DNA of the binary vector and flanking plant genomic DNA from T(1) plants.