Lifetime extension of in‐core self‐powered neutron detector using new emitter materials

In this paper, new in‐core self‐powered neutron detector emitter candidate materials, ie, vanadium, cobalt, and silver, have been examined in their lifetimes compared with the commonly used rhodium emitter. Using a new quantitative lifetime evaluation model, the lifetimes of vanadium and cobalt were determined to be longer than that of rhodium, but these materials were also shown to have the disadvantage of low signal intensities. Under normal operating conditions, we showed that rhodium emitter can be used for 2 cycles of pressurized water reactors (PWRs) with lifetime of 4.35 years, whereas silver can be used for 5 cycles of PWRs with lifetime of 8.04 years. Three sensitivity tests were performed for rhodium and silver about (1) the emitter size, (2) the fuel assembly burnup, and (3) the emitter temperature variations. From the test results, we observed that the lifetimes of rhodium and silver emitters remained 2 and 5 cycles long, respectively. We concluded that silver can significantly extend the in‐core detector's lifetime in PWR operation.     

Saliency-weighted graphs for efficient visual content description and their applications in real-time image retrieval systems

The exponential growth in the volume of digital image databases is making it increasingly difficult to retrieve relevant information from them. Efficient retrieval systems require distinctive features extracted from visually rich contents, represented semantically in a human perception-oriented manner. This paper presents an efficient framework to model image contents as an undirected attributed relational graph, exploiting color, texture, layout, and saliency information. The proposed method encodes salient features into this rich representative model without requiring any segmentation or clustering procedures, reducing the computational complexity. In addition, an efficient graph-matching procedure implemented on specialized hardware makes it more suitable for real-time retrieval applications. The proposed framework has been tested on three publicly available datasets, and the results prove its superiority in terms of both effectiveness and efficiency in comparison with other state-of-the-art schemes.     

The machine layout within a TFT-LCD bay with a multiple-stacker crane in-line stocker

In this paper, we study the machine layout problem in a TFT-LCD (thin-film transistor liquid-crystal display) bay with a multiple-stacker crane in-line stocker. Unlike other material-handling systems, such as automated guided vehicles and conveyors that only have a transportation function, in-line stockers have both transportation and storage functions. They rely on stacker cranes to perform their transportation function. The in-line stocker in a TFT-LCD bay is often divided into zones. Each zone is served by a stacker crane. Due to its multiple-zone in-line stocker, solving a TFT-LCD bay's machine layout requires us to determine not only the positions of the machines, but also the zone division design. The objectives include the minimisation of total flow distance and the workload balance between stacker cranes. We propose a layout procedure that adopts heuristic and mathematical approaches to assist us in accomplishing the aforementioned tasks. An example problem mimicking a real-case problem was solved to illustrate the proposed layout procedure. The layout design found by the proposed layout procedure was validated with computer simulations. It was also compared with layouts obtained by approaches proposed by other researchers. The simulation and comparison results demonstrate the capability of the proposed layout method in producing a feasible and good machine layout in a TFT-LCD bay with a multiple-stacker crane in-line stocker.     

Intercalating dye as an acceptor in quantum-dot-mediated FRET

Fluorescence resonance energy transfer (FRET) is a popular tool to study intermolecular distances and characterize structural or conformational changes of biological macromolecules. We investigate a novel inorganic/organic FRET pair with quantum dots (QDs) as donors and DNA intercalating dyes, BOBO-3, as acceptors by using DNA as a linker. Typically, FRET efficiency increases with the number of stained DNA linked to a QD. However, with the use of intercalating dyes, we demonstrate that FRET efficiency at a fixed DNA:QD ratio can be further enhanced by increasing the number of dyes stained to a DNA strand through the use of an increased staining dye/bp ratio. We exploit this flexibility in the staining ratio to maintain a high FRET efficiency of >0.90 despite a sixfold decrease in DNA concentration. Having characterized this new QD-mediated FRET system, we test this system in a cellular environment using nanocomplexes generated by encapsulating DNA with commercial non-viral gene carriers. Using this novel FRET pair, we are able to monitor the configuration changes and fate of the DNA nanocomplexes during intracellular delivery, thereby providing an insight into the mechanistic study of gene delivery.     

Fluorinated xerogel-derived microelectrodes for amperometric nitric oxide sensing

An amperometric fluorinated xerogel-derived nitric oxide (NO) microelectrode is described. A range of fluorine-modified xerogel polymers were synthesized via the cohydrolysis and condensation of alkylalkoxy- and fluoroalkoxysilanes. Such polymers were evaluated as NO sensor membranes to identify the optimum composition for maximizing NO permeability while providing sufficient selectivity for NO in the presence of common interfering species. By taking advantage of both the versatility of sol-gel chemistry and the "poly(tetrafluoroethylene)-like" high NO permselective properties of the xerogels, the performance of the fluorinated xerogel-derived sensors was excellent, surpassing all miniaturized NO sensors reported to date. In contrast to previous electrochemical NO sensor designs, xerogel-based NO microsensors were fabricated using a simple, reliable dip-coating procedure. An optimal permselective membrane was achieved by synthesizing xerogels of methyltrimethoxysilane (MTMOS) and 20% (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trimethoxysilane (17FTMS, balance MTMOS) under acid-catalyzed conditions. The resulting NO microelectrode had a conical tip of approximately 20 microm in diameter and approximately 55 microm in length and exhibited sensitivities of 7.91 pA x nM (-1) from 0.2 to 3.0 nM (R (2) = 0.9947) and 7.60 nA x microM (-1) from 0.5 to 4.0 microM ( R (2) = 0.9999), detection limit of 83 pM (S/ N = 3), response time ( t 95%) of <3 s, and selectivity (log K NO, j (amp)) of -5.74, <-6, <-6, <-6, <-6, -5.84, and -1.33 for j = nitrite, ascorbic acid, uric acid, acetaminophen, dopamine, ammonia/ammonium, and carbon monoxide. In addition, the sensor proved functional up to 20 d, maintaining >or=90% of the sensor's initial sensitivity without serious deterioration in selectivity.     

Particle-reinforced aluminum matrix composites produced from powder mixtures via friction stir processing

Particle-reinforced aluminum matrix composites were produced from powder mixtures of aluminum and silicon by using multiple passages of friction stir processing (FSP). In the composites, the Si particles with an average size of ∼1.5 μm are uniformly dispersed in the aluminum matrix which has a fine-grained structure (∼2 μm). The strengthening mechanism of the composites is discussed. It indicates that the fine grain size of aluminum, the Orowan strengthening due to intragranular particles and the dislocations generated by thermal mismatch all contribute significantly to the composite yield strength.     

ZrO2/hydroxyapatite coating on titanium by electrolytic deposition

In this study, hydroxyapatite (HA) was coated on a titanium (Ti) substrate over a ZrO(2) layer by the electrolytic deposition method, this double layer coating was then compared with a single layer coating of HA. The HA layer was used to increase the bioactivity and osteoconductivity of the Ti substrate, and the ZrO(2) layer was intended to improve the bonding strength between the HA layer and Ti substrate, and to prevent the corrosion of the Ti substrate. The electrolytic deposition formed an HA layer with a thicknesses of approximately 20 mum, which adhered tightly to the Ti substrate. The bonding strength of the HA/ZrO(2) double layer coating on Ti was markedly improved when compared to that of the HA single coating on Ti. The improvement in bonding strength with the use of a ZrO(2) base layer was attributed to the resulting increase in chemical affinity of the ZrO(2) to the HA layer and to the Ti substrate. The osteoblast-like cells cultured on the HA/ZrO(2) coating surface, proliferated in a similar manner to those on the HA single coating and on the pure Ti surfaces. At the same time, the corrosion resistance of Ti was improved by the presence of the ZrO(2) coating, as shown by a potentiodynamic polarization test.     

Redispersible drug nanoparticles prepared without dispersant by electro-spray drying

The redispersibility of drug nanoparticles is critical in the formulation development of oral solid dosage forms from drug nanosuspensions. To address this issue, various drying techniques such as, spray drying, fluidized bed drying, etc. have been developed based on freeze drying. In this work, redispersible dried powders were successfully prepared from drug nanosuspensions without the use of dispersant by applying an electrical potential to the nozzle during the spray drying process. The applied voltage, not the concentration of the nanosuspension, was critical in determining the redispersibility. Despite the high electric field, the particle morphology and crystallinity were not dependent on the applied voltage, which suggests that the drug crystals were not damaged. This novel technique could broaden the applicability of spray drying technology and allow for novel formulations of drug nanoparticles.