Peptide-nucleic acid-modified ion-sensitive field-effect transistor-based biosensor for direct detection of DNA hybridization

Here, we report the development of a peptide-nucleic acid (PNA)-modified ion-sensitive field-effect transistor (IS-FET)-based biosensor that takes advantage of the change in the surface potential upon hybridization of a negatively charged DNA. PNA was immobilized on a silicon nitride gate insulator by an addition reaction between a maleimide group introduced on the gate surface, the succinimide group of N-(6-maleimidocaproyloxy) succinimide, and the thiol group of the terminal cysteine in PNA. The surface was characterized after each step of the reaction by X-ray photoelectron spectroscopy analysis, and the kinetic analysis of the hybridization events was assessed by surface plasmon resonance. In addition, we measured the -potential before and after PNA-DNA hybridization in the presence of counterions to investigate the change in surface charge density at the surface-solution interface within the order of the Debye length. On the basis of the zeta-potential, the surface charge density, DeltaQ, calculated using the Grahame equation was approximately 4.0 x 10(-3) C/m2 and the estimated number of hybridized molecules was at least 1.7 x 10(11)/cm2. The I-V characteristics revealed that the PNA-DNA duplexes induce a positive shift in the threshold voltage, VT, and a decrease in the saturated drain current, ID. These results demonstrate that direct detection of DNA hybridization should be possible using a PNA-modified IS-FET-based biosensor. PNA is particularly advantageous for this system because it enables highly specific and selective binding at low ionic strength.     

Tacticity control by conformational isomerization in free radical polymerization of acrylate

Contribution of conformational isomerization to polymer tacticity has been studied in free radical polymerization of (−)-menthyl 2-acetamidoacrylate with azo initiators. It has been demonstrated that the chain end of the growing polymer radical, which is generated from the s-trans and s-cis conformers of monomer, produces stereoselectively new R and S configurational quaternary carbons, respectively, for the attack of monomer. In addition, polymerization reactivity of both conformers is indistinguishable under the present conditions, and the polymerization is considered to proceed through a chain-end controlled mechanism, which excludes a penultimate unit effect on tacticity in the polymerization. The results obtained would give a clue to understand an origin of tacticity in conventional free radical polymerization of acrylates.     

Physical properties of acrylic copolymer emulsions using poly(vinyl alcohol) as a protective colloid in comparison with those using surfactants

Properties of copolymer emulsions of methyl methacrylate and butyl acrylate prepared using poly(vinyl alcohol) (PVA) as a protective colloid have been studied and compared with those prepared using anionic and anionic/non‐ionic surfactants. The emulsions with PVA revealed a Newtonian flow, while those with surfactants had a thixotropic flow. Cast films of the emulsions with PVA afforded much larger tensile strengths, higher Young's moduli, and poorer resistance to water compared with those with surfactants. Adhesive layer composed of the copolymers with PVA revealed markedly higher creep resistance to shearing stress, while that with surfactants had poor resistance; these phenomena appear to arise from the canal‐like morphology of PVA in the former cast films, while the surfactants in the latter existed in island morphology. © 2000 Society of Chemical Industry     

Remarks on the time-varying H∞ Riccati equations

In this paper we establish some useful properties of three Riccati equations appearing in the standard H_∞-control problems for continuous and discrete-time time-varying systems. We then give necessary and sufficient conditions for the existence of a suboptimal controller by three conditions involving two independent Riccati equations with a coupling inequality.     

Study of lightning current by remanent magnetization

A study of remanent magnetization is made at the areas of lightning strikes. In the case of triggered lightning (Okushishiku, Hokuriku district), the magnetic direction of the specimens shows a clockwise rotation pattern around the point of lightning strike. At an archaeological site in Miyagi Prefecture, an anticlockwise pattern of the magnetic direction was detected. These results indicate that a stable remanent magnetization is acquired by the strong magnetic field induced surrounding the lightning current, both in negative and positive lightning flashes. Also, a detailed analysis of magnetization clarifies the electric current flow underground caused by the lightning. The study of remanent magnetization will become a useful method to elucidate the path of the lightning current. © 1998 Scripta Technica, Electr Eng Jpn, 123(4): 41–47, 1998     

Permeability properties of isometrically temperature-responsive poly(acrylic acid)-graft- oligo(N-isopropylacrylamide) gel membranes

A series of temperature-responsive hydrogels were prepared by grafting oligo(N-isopropylacrylamide) (ONIPAAm) chains onto a crosslinked poly(acrylic acid) (PAAc) network, intending an application to drug delivery systems (DDS). Cloud points and swelling ratios of the obtained PAAc-graft-ONIPAAm gels were measured as a function of temperature under various pH conditions. At pH > 4.5, the clear cloud points were observed at 31–33°C, which were almost the same values as that of poly(N-isopropylacrylamide) (PNIPAAm), whereas swelling/shrinkage phenomenon was not observed in the temperature range 25–45°C. It seemed that grafted ONIPAAm chains underwent the coil-to-globule transition, while the crosslinked PAAc network remained unchanged, due to the anionic charges on the main chains. In the presence of NaCl in the buffer solution, the phase transition temperature was slightly lowered. To assess the applicability of these temperature-responsive PAAc-graft-ONIPAAm gels to DDS, permeability of theophylline through the gel membranes was measured as a function of temperature. At a temperature below the cloud point, the permeability of theophylline was low, whereas it was high at an elevated temperature above the cloud point. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1027–1034, 1998     

An energy conversion method by using density difference of water

This paper proposes a new method which produces electric energy by utilizing the density difference of water by means of a “chimney effect.” The density difference of water occurs in two ways, i.e., differences of water temperature and consistency of suitable materials such as salt. For instance, water heated by solar energy is pointed out as an example of the former, while fresh water of a river versus seawater and seawater versus concentrated salt water may account for the latter. This paper also considers the three foregoing cases in a practical way. The analysis estimates that the proposed method generates energy of several hundreds or more, and ten thousands and millions of kilowatts in the respective cases. The amount of energy extracted in the third case is compared with that of the usual electric power stations using nuclear energy. The method is considered as a kind of so-called renewable energy conversion system which is free of CO₂, high-energy density and is controllable. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (2): 10–18, 1997     

Grain-Boundary Viscosity of BaO-Doped SiC

Internal friction characterization of the viscosity of a residual SiO₂/BaO glass, segregated to grain boundaries of polycrystalline SiC, is presented. The anelastic relaxation peak of internal friction, arising from viscous slip along grain boundaries wetted by a glass phase, is analyzed. Two SiC polycrystals, containing SiO₂/BaO glasses with different compositions, are studied and compared with a SiC polycrystal containing only pure SiO₂. The internal friction peak is first analyzed with respect to its shift upon frequency change. This analysis allows quantitative assessment of both the intrinsic viscosity and the activation energy for viscous flow of the grain-boundary phase. Both parameters markedly decrease with increasing amounts of BaO dopant, which is consistent with data reported in the literature on SiO₂ and SiO₂/BaO bulk glasses with the same nominal composition. Analysis of the peak morphology is also attempted, considering the evolution of peak width while varying the grain-boundary glass composition. Moreover, the role of microstructural parameters, such as the distributions of grain size and grain-boundary angles, on the broadening of the internal friction peak is addressed, and a procedure is proposed that allows quantitative evaluation of the activation energy for viscous flow of intergranular glass merely from the width of the internal friction peak.     

Study of impingement cooling of heat sinks for LSI packages with longitudinal fins

This paper describes an experimental and a semi-empirical study on the impingement cooling characteristics of heat sinks with longitudinal fins of a type suitable for LSI packages. The experiments were performed with a variety of different fins. To enhance impingement cooling, one long rectangular inlet orifice (slit) over the center of the heat sink was found to offer the best structure. The optimum orifice width is about 1/6 of the base width of the heat sink. The thermal resistance at a fixed volumetric flow rate and orifice width varies little with size of the gap between the fin tops and inlet orifice, but gaps near 2 mm slightly lower the resistance. Correlations are proposed between the thermal resistance of the heat sink and the geometry of the longitudinal fins. The accuracy of the predicted thermal resistances was found to be within ±25% of the experimental data. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(8): 537–553, 1996     

Association between Equol Production Status and Nonalcoholic Steatohepatitis

Equol is a metabolite of daidzein, a major soybean isoflavone with estrogenic and antioxidant activities. As the production of equol depends on the presence of certain members of the intestinal microflora, not all individuals can produce equol. We examined the relationship between NASH histological features and equol production. In an animal model, obese OLETF rats were intraperitoneally injected with a porcine serum to augment liver fibrogenesis. Equol-rich soy product, SE5-OH was orally administered during the experimental period. Treatment with SE5-OH markedly attenuated the development of liver fibrosis and expression of alpha-smooth muscle actin. In clinical research, 38 NAFLD patients (13 men and 25 women) were included. The degree of fibrosis and ballooning in equol-nonproducers was significantly higher than in equol-producers in women. The percentage of nonproducers with NAFLD activity score (NAS) ≥ 5 was significantly higher than that of producers. None of the histological features were significantly different between nonproducers and producers in men. Decision tree analysis identified predictors for NAS ≥ 5 in women. The status of equol production was the strongest predictor, followed by fasting glucose. Since equol can be noninvasively detected in urine, it can be applied as a screening tool for the progression of NASH in women.