Local oxidation using scanning probe microscope for fabricating magnetic nanostructures

Local oxidation technique using atomic force microscope (AFM) was studied. The local oxidation of ferromagnetic metal thin films was successfully performed by AFM under both contact and dynamic force modes. Modification of magnetic and electrical properties of magnetic devices fabricated by the AFM oxidation was achieved. Capped oxide layers deposited on the ferromagnetic metal films are advantageous for stable oxidation due to hydrophilic surface of oxide. The oxide layer is also expected to prevent magnetic devices from degradation by oxidation of ferromagnetic metal. As for modification of magnetic property, the isolated region of CoFe layer formed by nanowires of CoFe-oxide exhibited peculiar characteristic attributed to the isolated magnetization property and pinning of domain wall during magnetization reversal. Temperature dependence of current-voltage characteristic of the planar-type tunnel junction consisting of NiFe/NiFe-oxide/NiFe indicated that the observed current was dominated by intrinsic tunneling current at the oxide barrier.     

Specificity of immobilized metal affinity-based IMAC/C18 tip enrichment of phosphopeptides for protein phosphorylation analysis

We have developed a simple, highly specific enrichment procedure for phosphopeptides, by increasing the specificity of an immobilized metal affinity column (IMAC) without using any chemical reaction. The method employs a biphasic IMAC-C18 tip, in which IMAC beads are packed on an Empore C18 disk in a 200-microL pipet tip. Phosphopeptides are separated from non-phosphopeptides on the IMAC in an optimized solvent without any chemical reaction, then desorbed from the IMAC using a phosphate buffer, reconcentrated, and desalted on the C18 disk. The increase in selectivity was achieved by (a) using a strong acid to discriminate phosphates from carboxyl groups of peptides and (b) using a high concentration of acetonitrile to remove hydrophobic non-phosphopeptides. The entire procedure was optimized by using known phosphoproteins such as Akt1 kinase and protein kinase A. Although it was difficult to detect phosphopeptides in MALDI-MS spectra of tryptic peptide mixtures before enrichment, after the IMAC procedure, we could successfully detect phosphopeptides with almost no non-phosphopeptides. Next, we constructed an array of IMAC-IMAC/C18 tips, such that number of arrayed tips on a 96-well plate could easily be changed depending on the loading amount of sample. Applying this approach to mouse forebrain resulted in the identification of 162 phosphopeptides (166 phosphorylation sites) from 135 proteins using nano-LC/MS.     

Visual color matching under various viewing conditions

In this article, we provide colorimetry data for which it was judged that the colors between different media matched under various viewing conditions. Painted color patches, a monitor, and printed color patches were used in the color matching experiments, in which we compared the appearances of the painted color patch and the monitor, or the monitor and the printed color patch, using the method of constant stimuli. The nine types of viewing conditions we used could be envisaged to occur when comparing different device outputs indoors. The experimental data obtained were compared with corresponding colors predicted with the use of five types of color appearance model, including color appearance formulae. We found that when the viewing conditions were the same for the different media, there was good agreement between the experimental data and the CIECAT94 model. And by adjusting the brightness induction and the chromatic induction factors, it was possible to improve conformity for the lightness and the chromaticity. Moreover, it was possible to improve the white point shift, which cannot be adjusted with the use of optimized parameters by introducing incomplete adaptation. By optimizing the parameters and introducing incomplete adaptation, it is possible to make the mean color difference ΔE between the corresponding color and the color matching point less than 10 CIELAB units for all of the viewing conditions.     

Optimizing precision overhead for x86 processors

It is a major challenge for a Java JIT compiler to perform single-precision floating-point operations efficiently for the x86 processors. In previous research, the double-precision mode is set as the default precision mode when methods are invoked. Sophisticated approaches then use heuristic approaches to optimization by considering the trade-offs between roundings and mode switches. However, this convention introduces redundant mode switches across method boundaries. Furthermore, methods that include both single- and double-precision operations cannot switch the mode, even if single-precision operations are dominant. We propose a new approach to these problems. We eliminate redundant mode switches by ignoring the default precision mode and calling a method in the same precision mode as the caller. For methods that include both single- and double-precision methods, we reduce the overhead of rounding by isolating code segments of a given method that should be executed in the single-precision mode. We implemented our approach in IBM's Just-in-Time compiler, and obtained experimental results demonstrating that, in SPECjvm98, it consistently shows the best performance in any configuration of benchmark programs, inline policies, and processor architectures compared with previous research approaches. Copyright © 2004 John Wiley & Sons, Ltd.     

Statistical Analysis of the Fatigue Life Distribution of Monolithic Silicon Nitride

Cyclic fatigue testing of silicon nitride ceramics was performed at a frequency of f = 150 Hz and a stress ratio of R = 0.1 using a piezoelectric bimorph fatigue device. Based on the method proposed by Fett and Munz, a fatigue crack growth diagram ( K ₁– V diagram) was estimated from fatigue lifetime distribution data. A change in the slope of the K _I– V diagram was observed. A statistical analysis for predicting the lifetime of ceramics exhibiting a transition in a K _I– V diagram was devised on the basis of this observation. Analytical results obtained with this method showed good agreement with experimental data.     

Nitric oxide formation and carbon monoxide decay in the post-reaction zone of a premixed propane — air flat burner flame

Concentrations of the combustion products, especially carbon monoxide and nitric oxide, from a propane — air premixed flat burner flame were measured along the gas stream beyond the flame, and the results were examined in conjunction with chemical-kinetic calculations. It was concluded that the formation and stabilizing (with fall of temperature) of nitric oxide in stoichiometric or fuel-lean flames can be predicted by two reactions, O + N₂ = NO + N and N + O₂ = NO + O, and that the relative discrepancy between kinetic and simplified-partial-equilibrium models near the flame decreases downstream. For fuel-rich flames, very rapid nitric oxide formation was observed in the reaction zone; this cannot readily be explained by the above reactions in the post-reaction zone even if oxygen-atom ‘overshoot’ is taken into account. For example, at equivalence ratio f = 1.4, the necessary oxygen-atom concentration in the reaction zone would be more than 3000 times the chemical equilibrium concentration. Some reactions other than the above may need to be taken into account. The excess concentration of carbon monoxide observed just beyond the fuel-lean flame disappears rapidly along the gas flow, within about 3 ms. Its decay rate is considered to be dependent on a recombination reaction, H + OH + M = H₂O + M, while the conversion reaction, CO + OH = CO₂ + H, is so rapid that it can be presumed to be in partial equilibrium immediately after the flame.     

Detection and isolation of Escherichia coli with a coding gene for enteroaggregative Escherichia coli heat-stable enterotoxin 1 from food and comparison with fecal isolates

Enteroaggregative Escherichia coli heat-stable enterotoxin 1 (EAST1) was originally regarded as a putative enterotoxin of enteroaggregative Escherichia coli. Although its etiological role has not yet been elucidated, it has been epidemiologically suggested that some strains of E. coli possessing EAST1-coding gene (astA) but no other identifiable pathogenic properties comprise a new group of diarrhea-associated E. coli (EAST1EC). However, the source of the organisms and their prevalence in foods are still obscure. In this study, methods for detection of the organisms in foods heavily contaminated with coliforms were evaluated and properties of the isolated strains were compared with those of fecal strains. Four enrichment methods (brilliant green lactose bile broth, E. coli, lauryl tryptose broth, and a combination of brain heart infusion broth and tryptone phosphate broth) were evaluated through inspection of 115 samples. PCR showed positive results in 26 samples after enrichment with a combination of brain heart infusion broth and tryptone phosphate broth, and EAST1EC was successfully isolated from 18 samples. Fifteen samples showed a positive reaction in the PCR test after enrichment by the other methods, and the organisms were isolated from only 10 specimens. The highest prevalence of EAST1EC was found in animal products (16 of 54, 29.6%); the organism was rarely found in foods of plant origin (2 of 45, 4.4%) or fishery products (1 of 16, 6.3%). Although EAST1EC is unexpectedly common in animal products, its potential as a human pathogen remains uncertain because the possession of some virulence properties differs significantly between strains from fecal specimens and those from foods. Some food isolates, however, possess the same characteristics as diarrheal isolates do. It is necessary to clarify the pathogenicity of EAST1EC and the significance of food as a source of infection.     

Improvement of bacterial cellulose production by addition of agar in a jar fermentor

Bacterial cellulose (BC) was produced by Acetobacter xylinum BPR 2001 and its acetan nonproducing mutant EP1 in corn steep liquor-fructose medium in a 10-l jar fermentor supplemented with different agar concentrations ranging from 0% to 1.0% (w/v). The BC productivity of the two strains was increased by adding agar. The maximum BC production of BPR 2001 at an agar concentration of 0.4% was 12.8 g/l compared with 8 g/l without agar. The mutant EP1 produced 11.6 g/l of BC at an agar concentration of 0.6%, while only 5.5 g/l was produced in the control. Enhanced productivity is associated with an increase in viscosity of the culture, dispersion of BC pellets, and number of free cells due to agar addition, suggesting that acetan produced by BPR 2001 has a critical role in enhanced BC production.     

Phosphatidylcholine hydroperoxide levels in human plasma are lower than previously reported

The quantification of PC hydroperoxide (PCOOH) in human plasma was studied by HPLC with chemiluminescence detection (HPLC-CL). We identified for the first time the monohydroperoxide of 1-palmitoyl-2-linoleoyl-PC hydroperoxide (PC 16∶0/18∶2-OOH) in plasma by LC-MS and HPLC-CL. The standard compound, PC 16∶0/18∶2-OOH (synthetic PCOOH), as well as PCOOH from egg yolk, was used. Comparison of the PCOOH concentration in each participant's plasma as determined by use of a Finepak SIL NH₂ column with 2-propanol/methanol/water as the mobile phase (system A, the conventional method) gave a higher concentration than did an LC-18-DB column with methanol containing 0.01% triethylamine (system B). The mean PCOOH concentration for the 43 healthy volunteers was 55.1±30.4 pmol/mL (mean±SD) for system A and 16.3±9.9 pmol/mL for system B. Moreover, the main peak of the plasma extract appeared at a different time from that of synthetic PCOOH or egg yolk PCOOH in system A, whereas in system B plasma sample retention time practically corresponded to that of standard PCOOH. These findings confirm that the PCOOH plasma concentration is not so high as previously reported.