20 research outputs found
Shape effect of ceria in Cu/ceria catalysts for preferential CO oxidation
No full textCopper was deposited on different shapes of ceria supports (i.e., rods, cubes, and octahedra) and used as catalysts for preferential CO oxidation in excess amounts of hydrogen. When the same amount of copper was deposited, the copper content on the surface measured by X-ray photoelectron spectroscopy differed significantly, with more copper on the ceria octahedra. Copper seemed to migrate into the bulk ceria to a greater degree on the rods. The Cu/ceria-octahedra showed the highest activity of 95% at 140 degrees C among the three shapes, whereas the Cu/ceria-rods showed higher CO conversion than the Cuiceria-octahedra at higher temperatures. The Cu/ceria-octahedra showed no activity degradation for CO conversion at 140 C over 100 h, whereas the activity decreased by 13% for Cu/ceria-rod and 32% for Cu/ceria-cube at the same temperature. The metals Au and Pt were also deposited on the different shapes of ceria, and their activity and selectivity were evaluated. (C) 2010 Elsevier B.V. All rights reserved
Chemical doping-assisted shape transformation of block copolymer particles
No full textShape-tunable block copolymer (BCP) particles have attracted significant attention due to their applications as smart materials. Herein, we report iodine (I2)-mediated doping of polystyrene-block-polybutadiene (PS-b-PB) particles as a facile strategy to transform spherical BCP particles into nonspherical shaped particles. Upon introducing the I2 molecules to internally phase-separated spherical PS-b-PB particles, I2 selectively reacts with the double bonds in PB blocks while leaving the PS block unaffected. Monitoring the shape-transformation process reveals a gradual structural transition from spheres to oblates and ellipsoids as a function of reaction time, consistent with the increasing conversion of the double bonds into I2-doped cation radicals. Consequently, the interfacial tension of I2-doped PB blocks decreases, neutralizing the interfacial interaction of BCP and its surroundings, thereby restructuring the spherical particles into shape-anisotropic forms. Furthermore, the versatility of I2-mediated shape transition is demonstrated by applying the same chemistry to polystyrene-block-poly(4-vinylpyridine) BCP particles. Finally, spheroidal particles doped with I2 exhibit photothermal heating behavior, highlighting their potential application as photothermal agents.,Iodine-mediated chemical modification approach was developed for the facile shape transformation of block copolymer colloidal particles.,
Modeling and experiments of near-field thermophotovoltaic conversion: A review
No full textThis article provides an in-depth review of charge transport models utilized to analyze the performance of near-field thermophotovoltaic (NF-TPV) devices, and a comprehensive examination of NF-TPV experiments performed to date. Researchers have used several models to theoretically analyze NF-TPV devices; however, each model can result in different performances of NF-TPV devices, particularly due to characteristics of near field thermal radiation. For clarification, we sort up-to-date analysis models into four categories; the analytical approximation model, detailed balance analysis, minority carrier separation (MCS) model, and Poisson-drift- diffusion (PDD) model. Key assumptions of each model are enumerated, and the calculated results by each model are compared. For the review of experimental works, we first sort NF-TPV experiments according to the manner of gap control into positioner-, spacer-, and MEMS-based approaches. Then, we introduce the primary design configuration of each approach and the compelling experimental results achieved by state-of-the-art studies. In addition, advanced concepts of hybrid devices and multi-junction PV cells, proposed to further improve NF-TPV performance, are briefly introduced.
Helical magnetic nano-machines with chiral plasmonics
No full textMagnetic micro/nano-machines, driven by external magnetic fields, offer promising applications in drug delivery, disease treatment, and biological research due to their precise controllability and biocompatibility. However, moving through the blood vessel requires nano-machines smaller than 500 nm, which not only exhibits strong Brownian motion so limited propulsion, but is also difficult to track them against blood cells and others. To overcome these challenges, this study introduce 250 nm long FePt helical nanomachines that are magnetically as well as chiroptically active, respectively enabling their propulsion and optical tracking against blood. We here explore their chiroptical properties theoretically and experimentally to track the motion of individual nano-machines. Furthermore, their actuation performances are evaluated under external magnetic fields, yielding the speed of 3.2 bodylength/s
Experimental study of the effect of dissolution on the gas diffusion layer in polymer electrolyte membrane fuel cells
No full textSecondary cancer-incidence risk estimates for external radiotherapy and high-dose-rate brachytherapy in cervical cancer: phantom study
No full textThis study was designed to estimate radiation-induced secondary cancer risks from high-dose-rate (HDR) brachytherapy and external radiotherapy for patients with cervical cancer based on measurements of doses absorbed by various organs. Organ doses from HDR brachytherapy and external radiotherapy were measured using glass rod dosimeters. Doses to out-of-field organs were measured at various locations inside an anthropomorphic phantom. Brachytherapy-associated organ doses were measured using a specialized phantom that enabled applicator insertion, with the pelvis portion of the existing anthropomorphic phantom replaced by this new phantom. Measured organ doses were used to calculate secondary cancer risk based on Biological Effects of Ionizing Radiation (BEIR) VII models. In both treatment modalities, organ doses per prescribed dose (PD) mostly depended on the distance between organs. The locations showing the highest and lowest doses were the right kidney (external radiotherapy: 215.2 mGy; brachytherapy: 655.17 mGy) and the brain (external radiotherapy: 15.82 mGy; brachytherapy: 2.49 mGy), respectively. Organ doses to nearby regions were higher for brachytherapy than for external beam therapy, whereas organ doses to distant regions were higher for external beam therapy. Organ doses to distant treatment regions in external radiotherapy were due primarily to out-of-field radiation resulting from scattering and leakage in the gantry head. For brachytherapy, the highest estimated lifetime attributable risk per 100,000 population was to the stomach (88.6), whereas the lowest risks were to the brain (0.4) and eye (0.4); for external radiotherapy, the highest and lowest risks were to the thyroid (305.1) and brain (2.4). These results may help provide a database on the impact of radiotherapy-induced secondary cancer incidence during cervical cancer treatment, as well as suggest further research on strategies to counteract the risks of radiotherapy-associated secondary malignancies.restrictio
Experimental study on carbon corrosion of the gas diffusion layer in polymer electrolyte membrane fuel cells
No full textAnalysis of transient response of a unit proton-exchange membrane fuel cell with a degraded gas diffusion layer
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Sensitivity of radio-photoluminescence glass dosimeters to accumulated doses
No full textBackground: This study investigated the effect of accumulated doses on radio-photoluminescence glass dosimeters (RPLGDs) from measurements involving mega-voltage photons.
Methods: Forty-five commercially available RPLGDs were irradiated to estimate their dose responses. Photon beams of 6, 10, and 15 MV were irradiated onto the RPLGDs inside a phantom, which were divided into five groups with different doses and energies. Groups 1 and 2 were irradiated at 1, 5, 10, 50, and 100 Gy in a sequential manner; Group 3 was irradiated 10 times with a dose of 10 Gy; and Groups 4 and 5 followed the same method as that of Group 3, but with doses of 50 Gy and 100 Gy, respectively. Each device was subjected to a measurement reading procedure each time irradiation.
Results: For the annealed Group 1, RPLGD exhibited a linearity response with variance within 5%. For the non-annealed Group 2, readings demonstrated hyperlinearity at 6 MV and 10 MV, and linearity at 15 MV. Following the 100 Gy irradiation, the readings for Group 2 were 118.7 ± 1.9%, 112.2 ± 2.7%, and 101.5 ± 2.3% at 6, 10, and 15 MV, respectively. For Groups 3, 4, and 5, the responsiveness of the RPLGDs gradually decreased as the number of repeated irradiations increased. The percentage readings for the 10th beam irradiation with respect to the readings for the primary beam irradiation were 84.6 ± 1.9%, 87.5 ± 2.4%, and 93.0 ± 3.0% at 6 MV, 10 MV, and 15 MV, respectively.
Conclusions: The non-annealed RPLGD response to dose was hyperlinear for the 6 MV and 10 MV photon beams but not for the 15 MV photon beam. Additionally, the annealed RPLGD exhibited a fading phenomenon when the measurement was repeated several times and demonstrated a relatively large fading effect at low energies than at high energies.ope
