Study of reactivity control method by the application of gadolinium hydride to accelerator-driven system

A reactivity control method for accelerator-driven system (ADS) is studied for its ability to reduce both the maximum beam current and the load on the beam window. A burnable position (BP) assembly (with gadolinium and zirconium hydride pins) is applied to the ADS core for reactivity control, and various BP assembly optimizations (such as pin arrangement, BP assembly loading position, and BP composition) are performed to minimize the burnup reactivity swing. These optimizations lead to a decreased burnup reactivity swing that is as much as 82.5% less than the swing of non-BP-loaded core; furthermore, the maximum beam current is 12.5 mA. The reactor characteristics of the optimized BP-loaded ADS core are also analyzed to investigate how the introduction of BP assembly influences the system. Safety parameters (such as the Doppler coefficient and the coolant void reactivity) worsen with the introduction of BP assembly, and the total minor actinide transmutation amount decreases 30–40 kg because of the moderated neutrons and changed fuel composition.     

Diesel and bio-diesel fuel deposits on a hot surface

The aim of this study is to investigate the deposition remains of fuel droplets that impinge on a hot surface of Aluminum Alloy. The fuel droplets tested are diesel fuel (DF) and palm oil based ester that refers as a bio-diesel fuel (BDF). Temperatures of Aluminum Alloy surface and impingement interval of droplets are two parameters that were considered for various conditions of experiments. The maximum evaporation point (MEP) obtained from evaporation characteristics for each fuel was used as a reference point to decide the surface temperature of the Aluminum Alloy, where deposits of fuel were observed. The impingement interval was set at 3, 5 and 8 s with various surface temperatures of 320 °C and 370 °C. To understand the effect of heat transfer on deposition development, surface temperature of deposits was measured by using infrared thermometer. The deposition development depended on a few factors such as droplet impingement interval, hot surface temperature, type of fuel, and heat transfer of fuel deposits. BDF produced rapid development of fuel deposits comparing to DF.     

Time-dependent dielectric breakdown (TDDB) distribution in n-MOSFET with HfSiON gate dielectrics under DC and AC stressing

This paper discusses time-dependent dielectric breakdown (TDDB) in n-FETs with HfSiON gate stacks under various stress conditions. It was found that the slope of Weibull distribution of T_bd, Weibull β, changes with stress conditions, namely, DC stress, unipolar AC stress and bipolar AC stresses. On the other hand, the time evolution component of stress-induced leakage current (SILC) was not changed by these stresses. These experimental results indicate that the modulation of electron trapping/de-trapping and hole trapping/de-trapping by stress condition changes the defect size in high-k gate dielectrics. Therefore, the control of injected carrier and the characteristics of trapping can provide the steep Weibull distribution of T_bd, leading to long-term reliability in scaled CMOS devices with high-k gate stacks.     

Photooxidation of the antidepressant drug Fluoxetine (Prozac®) in aqueous media by hybrid catalytic/ozonation processes

This article examines the oxidative disposal of Prozac^® (also known as Fluoxetine, FXT) through several oxidative processes with and without UV irradiation: for example, TiO₂ alone, O₃ alone, and the hybrid methods comprised of O₃ + H₂O₂ (PEROXONE process), TiO₂ + O₃ and TiO₂ + O₃ + H₂O₂ at the laboratory scale. Results show a strong pH dependence of the adsorption of FXT on TiO₂ and the crucial role of adsorption in the whole degradation process. Photolysis of FXT is remarkable only under alkaline pH. The heterogeneous photoassisted process removes 0.11 mM FXT (initial concentration) within ca. 60 min with a concomitant 50% mineralization at pH 11 (TiO₂ loading, 0.050 g L⁻¹). The presence of H₂O₂ enhances the mineralization further to >70%. UV/ozonation leads to the elimination of FXT to a greater extent than does UV/TiO₂: i.e., 100% elimination of FXT is achieved by UV/O₃ in the first 10 min of reaction and almost 97% mineralization is attained under UV irradiation in the presence of H₂O₂. The hybrid configuration UV + TiO₂ + O₃ + H₂O₂ enhances removal of dissolved organic carbon (DOC) in ca. 30 min leaving, however, an important inorganic carbon (IC) content. In all cases, the presence of H₂O₂ improves the elimination of DOC, but not without a detrimental effect on the biodegradability of FXT owing to the low organic carbon content in the final treated effluent, together with significant levels of inorganic byproducts remaining. The photoassisted TiO₂/O₃ hybrid method may prove to be an efficient combination to enhance wastewater treatment of recalcitrant drug pollutants in aquatic environments.     

Design of novel biomimetic polymer gels with self-oscillating function

We report a novel biomimetic gel that undergoes autonomous swelling-deswelling oscillations without on-off switching of external stimuli, similar to heartbeat. The mechanical oscillation of gel was produced via oscillating chemical reaction, called the Belousov-Zhabotinsky (BZ) reaction. We have prepared an ionic gel consisting of the cross-linked poly(N-isopropylacrylamide) chain to which ruthenium tris(2,2′-bipyridine), a catalyst for the BZ reaction, was covalently bonded. The BZ reaction occurring within the gel matrix generates periodic redox changes of the catalyst moiety. This chemical oscillation is converted into the mechanical oscillation of the polymer network. As a result, the gel exhibits a periodical swelling-deswelling change. The self-oscillating behaviors of the gel were investigated in detail. When the gel size is smaller than the chemical wavelength, the redox change occurs homogeneously in the gel. In this case, the volume change is isotropic and the mechanical oscillation synchronizes with chemical oscillation without a phase difference. The period and amplitude can be controlled by changing the outer substrate concentrations. In the case of rectangular shape, chemical wave propagates along the length of the gel. The wavelength and velocity depend on the reaction rate of autocatalytic process as well as the diffusivity of the activator. The dynamic behavior that locally shrunken (or swollen) parts propagate was observed, similar to the peristaltic motion of worms. By using lithography technique, a ciliary motion actuator made of the gel has been demonstrated. These self-oscillating gels may be useful in a number of important applications to intelligent biomaterials such as pulse generator or chemical pacemaker, auto-mobile actuators or micropumps with peristaltic motion, device for signal transmission, etc.     

Evaluation of dioxin-like activities in settled house dust from Vietnamese E-waste recycling sites: relevance of polychlorinated/brominated dibenzo-p-dioxin/furans and dioxin-like PCBs

Few studies have investigated the human exposure to the ensemble of dioxin-related compounds (DRCs) released from uncontrolled e-waste recycling, especially from a toxic effect standpoint. This study evaluated the TCDD toxic equivalents (TEQs) in persistent extracts of settled house dust from two Vietnamese e-waste recycling sites (EWRSs) using the Dioxin-Responsive Chemically Activated LUciferase gene eXpression assay (DR-CALUX), combined with chemical analysis of PCDD/Fs, DL-PCBs, PBDD/Fs, and monobromo PCDD/Fs to determine their TEQ contribution. The CALUX-TEQ levels in house dust ranged from 370 to 1000 pg g(-1) in the EWRSs, approximately 3.5-fold higher than in the urban control site. In EWRS house dust, the concentrations of the unregulated PBDFs were 7.7-63 ng g(-1), an order of magnitude higher than those of regulated DRCs (PCDD/Fs and DL-PCBs), and PBDFs were also principal CALUX-TEQ contributors (4.2-22%), comparable to PCDD/Fs (8.1-29%). The CALUX-TEQ contribution of DRCs varied, possibly depending on thermal processing activities (higher PCDD/F-TEQs) and PBDE content in the waste (higher PBDF-TEQs). However, the percentage of unknown dioxin-like activities was high in all dust samples, indicating large contribution from unidentified DRCs and/or synergy among contaminants. Estimates of TEQ intake from dust ingestion suggest that children in the EWRSs may be adversely affected by DRCs from dust.     

Crystal structure refinement of A-type carbonate apatite by X-ray powder diffraction

Complete carbonate substitution at A-sites (OH) of low-crystallinity hydroxyapatite with near stoichiometric composition (i.e. Ca/P ratio of 1.65) was achieved by heating in a dry carbon dioxide flow at 1173 K for 64 h. The carbonate content was analysed by thermogravimetry and infrared absorption spectrometry; the chemical composition was determined to be Ca_9.9±0.1(PO₄)_6.00±0.1(CO₃)_0.9±0.1. The crystal structure and atomic configuration of the carbonate ion were determined by Rietveld refinement using X-ray powder diffraction data. This analysis revealed that the space group was monoclinic Pb with a = 0.9571(1), b = 1.9085(2), c = 0.68755(3) nm and γ = 119.847(7)°. The triangular planes of the carbonate ions were oriented parallel to the c- and a-axes, though there were two independent carbonate sites with occupancy factors of 0.56(1) and 0.34(1), where the triangles were oppositely rotated about the corresponding carbon atoms by 23° and −18°, respectively. The arrangement of the ions was disordered, which explains the lack of a thermal phase transition below 623 K.