Photo-induced aminobenzoate group formation on a polymeric photobase generator bearing N-phenylcarbamate groups and its application to color imaging material

A polymeric photobase generator bearing N-phenylcarbamate groups was prepared to generate aromatic amino groups upon irradiation and used for color imaging on a thin polymer film. Polymer bearing N-phenylcarbamate groups was prepared by copolymerization of methacryloyloxyethyl phenylcarbamate (MPC) and methyl methacrylate (MMA). The photochemical process of the polymer was monitored through the UV and IR absorption spectral analyses and contact angle measurements. Irradiation of the polymer led to the formation of aminobenzoate groups through the photo-Fries type rearrangement or cross-linking through the radical coupling reaction of N-phenylcarbamate groups. The cosinus values of contact angle (θ) of the polymer film decreased upon irradiation indicating that the polymer surface developed a hydrophobic property. A color image was produced by a diazocoupling reaction of the aminobenzoate groups which were produced in the irradiated area of the polymer film with phenolic or aromatic amino coupling agent. The yellow color was developed by resorcinol or aniline treatment, whereas the red color was produced by the naphthol AS or 1-naphthylamine treatment.     

A risk management approach to safety assessment of trenchless technologies for culvert rehabilitation

Proper functioning of culverts is not only critical to protecting the transportation system from flooding but also critical to maintaining the expected service life of the overall transportation system. During the service life of culverts, they deteriorate due to many reasons such as corrosion caused by road salt, blockage by debris and sediment, poor construction techniques, etc. Trenchless technologies have been used by several State Departments of Transportation (DOTs) to rehabilitate deteriorated drainage structures without disrupting the traffic and within a relatively short span of time. These technologies provide many benefits in terms of cost, time, quality, and expected service life. However, the safety aspects of these techniques have not been discussed and documented in detail probably due to the complexity and the lack of safety standards and specifications directly associated with the techniques. This paper discusses the application of a risk assessment framework to assess potential safety issues of currently available trenchless technologies for culvert rehabilitation. The findings of the study will provide additional information to improve the decision making process in selecting and planning culvert rehabilitation projects.     

Optimization of inverted bulk heterojunction polymer solar cells

We have successively fabricated inverted bulk heterojunction polymer solar cells employing ZnO and MoO₃ as electron and hole selective layers, respectively. The device structure is ITO/ZnO/P3HT: PCBM/MoO₃/Al. Differently from conventional polymer solar cells, ITO and Al work as electron and hole collecting electrodes in this inverted structure, respectively. We have found the optimal thickness of ZnO and MoO₃ to be 100 nm and 5 nm, respectively. The highest PCE was obtained to be 3.32% under AM 1.5 illumination at 1,000W/m², which is the highest PCE of inverted solar cells reported previously in the literature.     

The public's value of hydrogen fuel cell buses: A contingent valuation study

With the increasing interest in global warming, there has been intense international competition with regard to the introduction of the hydrogen (H₂) fuel cell (FC) bus, which represents a promising solution for the low-carbon age. With respect to the investment in H₂-based technology development and the expansion of H₂ FC vehicles, the consumer attitude is a crucial factor because the Korean government will consider it one of the most important factors in its decision to approve a large-scale introduction of H₂ FC buses. In this regard, this study measures the public's willingness to pay (WTP) for a large-scale introduction of H₂ FC buses in Korea by employing a survey approach termed the contingent valuation. Furthermore, to enhance statistical efficiency, this study employs the one-and-one-half-bound dichotomous choice method. The annual mean WTP estimate was KRW 4230 (USD 4.55) per household as of 2007. The estimate of the annual benefits to the affected residents was KRW 32.3 billion (USD 34.7 million). The results of this study are expected to be helpful in policy decisions related to the introduction of H₂ FC buses and investment in H₂ technology development.     

Affective same-different discrimination tests for assessing consumer discriminability between milks with subtle differences

Affective and analytical same-different discrimination tests for assessing the ability of consumers to discriminate between milks with subtle differences were designed by applying familiarization procedures to induce an affective/synthetic and analytical/synthetic perceptual strategy. The tests were then administered to 100 milk consumers and compared. In both same-different discriminations, consumers adopted a cognitive decision rule that used a β-strategy rather than a τ-strategy. Discrimination tests employing an affective/synthetic perceptual approach (which is the normal consumer perceptual process) resulted in higher discriminability than tests that employed an analytical/synthetic approach. Inter-individual differences in the consumer criteria (boundaries) used for same-different ratings were studied by examining the response distributions over the given response categories for the same pairs. According to the similarity of such response distributions, two different consumer segments were classified and their group discriminabilities differed significantly, with only the more sensitive group showing interactions between the affective/hedonic state and perceptual discriminability.     

Investigation of flame characteristics using various design parameters in a pulverized coal burner for oxy‐fuel retrofitting

In oxy‐coal combustion for carbon capture and storage, oxygen and recirculated CO₂ are used as oxidizers instead of air to produce CO₂‐rich flue gas. Owing to differences between the physical and chemical properties of CO₂ and N₂, the development of a burner and boiler system based on fundamental understanding of the flame type, heat transfer, and NOx emission is required. In this study, computational fluid dynamic analysis incorporating comprehensive coal conversion models was performed to investigate the combustion characteristics of a 30 MWth tangential vane swirl pulverized coal burner. Various burner design parameters were evaluated, including the influence of the burner geometry on the swirl strength, direct O₂ injection, and O₂ concentrations in the primary and secondary oxidizers. The flame characteristics were sensitive to the oxygen concentration in the primary oxidizer. The performance of direct O₂ injection around the primary oxidizer with low O₂ concentration was dependent on the mixing of the fuel and oxidizer. The predictions showed that swirl number adjustment and careful direct oxygen injection design are essential for retrofitting air‐firing pulverized coal burners as oxy‐firing burners.     

A monolithic three-axis micro-g micromachined silicon capacitive accelerometer

A monolithic three-axis micro-g resolution silicon capacitive accelerometer system utilizing a combined surface and bulk micromachining technology is demonstrated. The accelerometer system consists of three individual single-axis accelerometers fabricated in a single substrate using a common fabrication process. All three devices have 475-/spl mu/m-thick silicon proof-mass, large area polysilicon sense/drive electrodes, and small sensing gap (<1.5 /spl mu/m) formed by a2004 sacrificial oxide layer. The fabricated accelerometer is 7/spl times/9 mm/sup 2/ in size, has 100 Hz bandwidth, >/spl sim/5 pF/g measured sensitivity and calculated sub-/spl mu/g//spl radic/Hz mechanical noise floor for all three axes. The total measured noise floor of the hybrid accelerometer assembled with a CMOS interface circuit is 1.60 /spl mu/g//spl radic/Hz (>1.5 kHz) and 1.08 /spl mu/g//spl radic/Hz (>600 Hz) for in-plane and out-of-plane devices, respectively.     

Mammalian peroxiredoxin isoforms can reduce hydrogen peroxide generated in response to growth factors and tumor necrosis factor-alpha

Mammalian tissues express three immunologically distinct peroxiredoxin (Prx) proteins (Prx I, II, and III), which are the products of distinct genes. With the use of recombinant proteins Prx I, II, and III, all have now been shown to possess peroxidase activity and to rely on Trx as a source of reducing equivalents for the reduction of H2O2. Prx I and II are cytosolic proteins, whereas Prx III is localized in mitochondria. Transient overexpression of Prx I or II in cultured cells showed that they were able to eliminate the intracellular H2O2 generated in response to growth factors. Moreover, the activation of nuclear factor kappaB (NFkappaB) induced by extracellularly added H2O2 or tumor necrosis factor-alpha was blocked by overproduction of Prx II. These results suggest that, together with glutathione peroxidase and catalase, Prx enzymes likely play an important role in eliminating peroxides generated during metabolism. In addition, Prx I and II might participate in the signaling cascades of growth factors and tumor necrosis factor-alpha by regulating the intracellular concentration of H2O2.     

Three-dimensional quantitative structure-activity relationship study of nonsteroidal estrogen receptor ligands using the comparative molecular field analysis/cross-validated r2-guided region selection approach

A newly developed comparative molecular field analysis (CoMFA) technique, the cross-validated r2-guided region selection (CoMFA/q2-GRS) method, has been used to build a quantitative structure-activity relationship (3D-QSAR) for nonsteroidal estrogen receptor (ER) ligands. Ligands included in this study belong to a series of diethylstilbestrol (DES) and indenestrol analogues whose affinities for the mouse ER (mER) have been determined in our laboratory. The final model utilized 30 compounds and yielded a q2GRS (cross-validated r2, guided region selection) of 0.796, as compared to a q2 of 0.720 for conventional CoMFA, with a standard error of prediction of 0.594 at 3 principal components. This model was used to visualize steric and electrostatic features of the ligands that correspond with ER binding affinity. Results obtained from the CoMFA steric and electrostatic plots of this model have also been compared to information from the ER binding affinities of substituted estradiol analogues. This is in an effort to determine structural features of compounds in the CoMFA analysis that may correspond to those of the estradiol analogues and to further clarify the mode of binding of nonsteroidal ER ligands.     

Effects of various baffle designs on acoustic characteristics in combustion chamber of liquid rocket engine

Effects of various baffle designs on acoustic characteristics in combustion chamber are numerically investigated by adopting linear acoustic analysis. A hub-blade configuration with five blades is selected as a candidate baffle and five variants of baffles with various specifications are designed depending on baffle height and hub position. As damping parameters, natural-frequency shift and damping factor are considered and the damping capacity of various baffle designs is evaluated. Increase in baffle height results in more damping capacity and the hub position affects appreciably the damping of the first radial resonant mode. Depending on baffle height, two close resonant modes could be overlapped and thereby the damping factor for one resonant mode is increased exceedingly. The present procedure based on acoustic analysis is expected to be a useful tool to predict acoustic field in combustion chamber and to design the passive control devices such as baffle and acoustic resonator.