Least detectable concentration and dynamic range of three immunoassay systems using the same antibody

The least detectable concentration (LDC) and dynamic range (DR) of three immunoassay systems are compared using four distinct antibodies (all specific for estradiol but with different affinities) on each system. The systems evaluated include the industry standard, ELISA, and two biosensors, surface plasmon resonance and kinetic exclusion. In all cases, the measurements of inhibition curves (response vs estradiol concentration) were contracted to outside experts (the biosensor manufacturers themselves in the case of the biosensors), each of whom was supplied with the same blind samples. Each biosensor manufacturer also reported an estimate of the equilibrium dissociation constant (Kd) for each of the antibodies. The LDC and DR observed for the kinetic exclusion biosensor are consistent with an interpretation of Kd limited detection while that from the other biosensor and ELISA show limits of detection somewhat above those expected for Kd limited performance. The determined LDC and DR of each biosensor is self-consistent in the sense that none of the inhibition data contradicts theoretical limits associated with the Kd as measured on that system; however, some contradictions are apparent across platforms. The use of multiple antibodies of differing Kd improves confidence that the observed differences in performance are associated with the immunoassay system rather than the particular analyte.     

Large eddy simulation of swirling jet in a bluff-body burner

The large eddy simulation (LES) is applied to an unconfined swirling flow of an air surrounding a bluff-body having a central jet of air, and the complicated flowfield that involves the recirculation and vortex breakdown is investigated. The Smagorinsky model is used as the sub-grid scale model. The results of the present numerical simulation are compared with the experimental data of the mean and stochastic root mean square (RMS) variations of two velocity components. Although the inflow conditions are specified in a simple manner, the obtained numerical results are in reasonable agreement with the experiments, except for a part of RMS variation values near downstream of the bluff body. The present numerical calculations can successfully reproduce the two characteristics of the flow, i.e., an upstream recirculation zone established just downstream of the burner plane and the additional recirculation zone established at the more downstream location.     

Improving an immunoassay response to related polychlorinated biphenyl analytes by mixing antibodies

Immunoassays for detection of a class of closely related antigens, e.g., PCBs, have often been too specific (responding strongly to some members of the class and missing others) and no general method for adjusting the response has been described. In this paper, the difference in the response of a model immunoassay to different Kanechlors (Japanese commercial mixtures of PCBs, analogous to Aroclors in the United States) is reduced from 20- or 50-fold (depending on which antibody is used) to 3-fold when the antibodies are mixed at the proper ratio. A mathematical model based on competitive binding of two antibodies for up to four antigens has been developed and used to describe the assay performance and to predict optimum mix ratios for the antibodies used. The model (based on separate measurement of each antibody's effective Kd for each Kanechlor) provides an excellent fit to the measured mixed antibody assay response. The model is also successful in identifying cases where mixing monoclonal antibodies will not improve the response. It is thought the method described will have applicability in a variety of cases where the analytical goal is semiquantitative screening based on the total quantity of an unknown mixture of related compounds.     

Fast drive of displacement magnification mechanism with flexure hinge using loading type impact damper

A displacement magnification mechanism which uses flexure motion guide using elastic hinges can realize smooth frictionless motion but has poor vibration damping capability. An impact damper is a damping mechanism which uses collision energy to dissipate vibration energy. If the damper is used for vibration control of the flexure mechanism, it may be able to dissipate unexpected vibration without killing the merits of the flexure mechanism. In the paper, a loading type impact damper is applied to settle down transient vibration of a displacement magnification mechanism. We investigate differences of damping effect by setting conditions of the damper. It is shown that the impact damper can eliminate residual vibration at step response effectively without steady state error. The experimental displacement magnification mechanism with impact damper can settle down less than 1/5 of the response without the damper under appropriate setting conditions. Influence of natural frequency ratio between damper and displacement magnification mechanism is investigated. Influences of indentation at impact point are also examined.     

Photo-induced properties of anodic oxide films on Ti6Al4V

Photocatalytic activity and wettability of the anodic oxide layer on Ti6Al4V prepared by anodization in a sulfuric acid electrolyte are explored. The oxide is composed mainly of TiO₂ with V₂O₅, VO₂ and Al₂O₃. The crystal structure of the TiO₂ varies from anatase to rutile with the sulfuric acid concentration in the electrolyte. Anatase exhibits better photocatalytic activity compared with rutile, which is different from those on Ti and Ti-Nb-Sn alloy. Contact angles of the oxides decrease with ultraviolet light illumination, and hydrophilicity is observed in the rutile oxide. Both photocatalytic activity and hydrophilicity are inferior to the corresponding Ti and Ti-Nb-Sn alloy, which is explained by the presence of Al₂O₃ in the anodic oxide.     

Colloidal platinum in hydrogen-rich water exhibits radical-scavenging activity and improves blood fluidity

The 'colloidal platinum' stabilized with polyvinylpyrrolidone (Pt/PVP-colloid) was dispersed in hydrogen-rich water (HW; hydrogen concentration, 0.82 ppm; oxidation-reduction potential, -583 mV) or regular water (RW; <0.01 ppm, +218 mV). And we evaluated the antioxidant activity of Pt/PVP-colloid in HW or RW on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and improvement of blood fluidity under 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH)-induced oxidative stress. When applied with the 0.25-0.5 ppm Pt/PVP-colloid in RW or HW, the level of DPPH radicals decreased to 77.5-59.6% or 16.1-5.6%, in contrast to the level as high as 81.3% for HW alone, respectively, as measured by an electron spin resonance method. The horse blood, which was subjected to AAPH-induced oxidative stress, was incubated for 24 hr with RW or HW, and thereafter required 13.7 sec (100%) or 5.7 sec (42.3%) for passing through the micro-channels in a rheology equipment. When treated with 0.5-1.0 ppm Pt/PVP-colloid in RW or HW, the blood passage time in the micro-channels decreased dose-dependently to 9.7-7.3 sec (71.6-53.8%) or 4.3-1.3 sec (32.8-10.3%), and the rate of micro-channels clogged with erythrocyte aggregates decreased to 23.8-21.0% or 15.8-9.8%, respectively, from 42.8% for no addition of Pt/PVP. By scanning electron microscopy, AAPH-treated erythrocytes lost intact surface morphology on the membrane together with protrusions and without hollows, being indicative of impaired transforming ability, and the rate of erythrocyte agglutination was increased to 46.2%. When treated the horse blood with HW alone significantly decreased the rate of erythrocyte agglutination to 29.6%, whereas 1.0 ppm Pt/PVP-colloid in RW or HW decreased it to 24.1% or 21.1%, respectively. Thus, DPPH-radical-scavenging and erythrocyte-protecting effects of Pt/PVP-colloid in HW were superior to those of Pt/PVP-colloid in RW or Pt/PVP-free HW. The results could be mainly attributed to the enhanced antioxidant activity of Pt/PVP in HW, which may be due to captured-hydrogen on platinum.     

Enhanced radiosensitization by liposome-encapsulated pimonidazole for anticancer effects on human melanoma cells

The nitroimidazole-related hypoxic radiosensitizer, pimonidazole (Pmz) was encapsulated in liposome composed of dipalmitoylphosphatidylcholine, cholesterol and dipalmitoylphosphatidylglycerol (molar ratio = 1:1:0.2; diameter = 112.9 nm), and the radiosensitization was evaluated in human melanoma cells HMV-II. Cell proliferation was examined by WST-8 assay after X-ray irradiation in the presence of liposomal Pmz or free-Pmz under hypoxic conditions. On 7th day after X-ray irradiation of 5 Gy, cell proliferation decreased more markedly in the administration of liposomal Pmz than free-Pmz at equivalent Pmz doses. Chromatin fragmentation or nuclear condensation was observed in liposomal Pmz-treated HMV-II cells. Radiosensitization was enhanced dose-dependently along with Pmz amounts of 250-2000 microM contained in liposomal Pmz. Intracellular uptake was more abundant for liposomal Pmz for 60-240 min than for free-Pmz. Thus liposomal Pmz has a potential to overcome radiation resistance in hypoxia, owing to enhanced intracellular uptake by melanoma cells.     

Large eddy simulation of methane non-premixed flame using the laminar flamelet model

The large eddy simulation (LES) using the steady laminar flamelet model is applied to a simple turbulent jet flame with 33.2% H2, 22.1% CH4 and 44.7% N2 at the Reynolds number of 15,200 in order to validate the numerical methods and to investigate the flame structure. For the validation, the detailed experimental data of DLR-A flame is used. The numerical results are in reasonable agreement with experimental results except mass fractions of minor species. In the flow field, the break-down of the potential core, the vortex structure and the mixing intensity are well captured. In the combustion field, mass fractions of major species (H2O, CO2, CO) are well predicted quantitatively. Minor species are well predicted qualitatively. In the present study, the simulations conducted on the Cartesian and cylindrical grids with approximately 6.6× 10⁵ nodes are compared.     

Effect of Feedback Force Delays on the Operation of Haptic Displays

Recently, Virtual Reality (VR) technology has developed quickly, together with research conducted on various elemental and related technologies and research in various fields of its application. We experimented about delay times. The haptic media is very sensitive to the network delay and its jitter and packet loss. The analytic hierarchy process(AHP) is one of the methods used to evaluate physical phenomena as correctness of the human sensation. In consequence of its application to the present experiment, it was made clear that the haptic media could be estimated from the delay times. In this report, we experimented about the relation between the delay times and haptic sense. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Reaction stoichiometry between TiCl3 and NaAlH4 in Ti-doped alanate for hydrogen storage: The fate of the titanium species

In order to understand the final state of the TiCl₃ dopant during the dehydrogenation and rehydrogenation cycles of NaAlH₄, we determined the reaction stoichiometry between TiCl₃ and NaAlH₄ by measuring the amount of hydrogen evolution from NaAlH₄ with the varying TiCl₃ -load. We found that: (i) TiCl₃ reacted with 3 M equivalents of NaAlH₄ during the doping process of ball-milling, (ii) the Ti dopant continued to react with NaAlH₄ during the first dehydrogenation process until total six equivalents of NaAlH₄ were consumed, and (iii) Ti fixed Al, not NaH, so that Al became insufficient during the rehydrogenation process. These findings lead to the conclusion that the reaction stoichiometry between Ti and Al is 1:6, which probably yields TiAl₆ and plays a catalytic role in the hydrogen storage reactions of Ti-doped NaAlH₄.