A very exotic process of β-delayed fission of 180Tl is studied in detail by using resonant laser ionization with subsequent mass separation at ISOLDE (CERN). In contrast to common expectations, the ...fission-fragment mass distribution of the post-β-decay daughter nucleus 180Hg (N/Z=1.25) is asymmetric. This asymmetry is more surprising since a mass-symmetric split of this extremely neutron-deficient nucleus would lead to two 90Zr fragments, with magic N=50 and semimagic Z=40. This is a new type of asymmetric fission, not caused by large shell effects related to fragment magic proton and neutron numbers, as observed in the actinide region. The newly measured branching ratio for β-delayed fission of 180Tl is 3.6(7) × 10(-3)%, approximately 2 orders of magnitude larger than in an earlier study.
Abstract
Hysteresis loops exhibited by the thermal properties of undoped and 0.8 at.% W-doped nanocrystalline powders of VO
2
synthesized by means of the solution combustion method and compacted in ...pellets, are experimentally measured by photothermal radiometry. It is shown that: (i) the W doping reduces both the hysteresis loops of VO
2
and its transition temperature up to 15 °C. (ii) The thermal diffusivity decreases (increases) until (after) the metallic domains become dominant in the VO
2
insulating matrix, such that its variation across the metal-insulation transition is enhanced by 23.5% with W-0.8 at.% doping. By contrast, thermal conductivity (thermal effusivity) increases up to 45% (40%) as the metallic phase emerges in the VO
2
structure due to the insulator-to-metal transition, and it enhances up to 11% (25%) in the insulator state when the local rutile phase is induced by the tungsten doping. (iii) The characteristic peak of the VO
2
specific heat capacity is observed in both heating and cooling processes, such that the phase transition of the 0.8 at.% W-doped sample requires about 24% less thermal energy than the undoped one. (iv) The impact of the W doping on the four above-mentioned thermal properties of VO
2
mainly shows up in its insulator phase, as a result of the distortion of the local lattice induced by the electrons of tungsten. W doping at 0.8 at.% thus enhances the VO
2
capability to transport heat but diminishes its thermal switching efficiency.
Hysteresis loops in the emissivity of VO2 thin films grown on sapphire and silicon substrates by a pulsed laser deposition process are experimentally measured through the thermal-wave resonant cavity ...technique. Remarkable variations of about 43% are observed in the emissivity of both VO2 films, within their insulator-to-metal and metal-to-insulator transitions. It is shown that: i) The principal hysteresis width (maximum slope) in the VO2 emissivity of the VO2 + silicon sample is around 3 times higher (lower) than the corresponding one of the VO2 + sapphire sample. VO2 synthesized on silicon thus exhibits a wider principal hysteresis loop with slower MIT than VO2 on sapphire, as a result of the significant differences on the VO2 film microstructures induced by the silicon or sapphire substrates. ii) The hysteresis width along with the rate of change of the VO2 emissivity in a VO2 + substrate sample can be tuned with its secondary hysteresis loop. iii) VO2 samples can be used to build a radiative thermal diode able to operate with a rectification factor as high as 87%, when the temperature difference of its two terminals is around 17 °C. This record-breaking rectification constitutes the highest one reported in literature, for a relatively small temperature change of diode terminals.
1 wt%Rh/Ce-MCM-41 catalysts were synthesized using Ce-MCM-41 as support where Si/Ce molar ratio varied from 10 to 30 and 50. During hydrogen reduction process, metallic Rh particles were formed on ...the Ce-MCM-41 at around 130 °C with an average particle size 6.8 nm. These catalysts were tested in the ethanol steam reforming (ESR) under atmospheric pressure between 225 and 425 °C. Compared to Rh/MCM-41 catalyst, cerium introduction would significantly enhance both the catalytic activity and hydrogen yield by approximately 2–3 times. However, the amount and the method of Ce incorporation in the framework of MCM-41 could greatly impact the catalytic performance of the Rh/Ce-MCM-41 catalysts. The ethanol conversion at 425 °C over the Rh/Ce-MCM-41 catalysts increased from 90.0% to 95.1% and 99.9%, as the Si/Ce molar ratio increases from 10 to 30 and 50. However, product selectivity is almost independent of the cerium content. The direct hydrothermal method of introducing Ce into the framework of MCM-41 is much superior to the impregnation route in the ESR reaction. After 6 h of reaction, the catalysts remain the mesostructure and the chemical state of cerium ions unchanged. Trace coke with graphite-like structure deposited on the surface does not modify the catalytic performance.
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•Ce incorporation in the framework of MCM-41 is favorable to the reduction of Rh2O3.•Ce introduction profoundly enhance ethanol conversion and H2 yield by approximately 2–3 times.•The direct hydrothermal method of introducing Ce is much superior to the impregnation route.
•The usage of heat pipes into an absorption heat transformer is analyzed for energy saving.•The initial heat for a conventional AHT is reduced almost 25% by using heat pipes.•The COP enhances up to ...20%, if the all condenser heat is recovered by the evaporator inside an AHT.•The local heat transfer coefficients for the evaporator and condenser were of 720W/m2°C and 250W/m2°C respectively.
This study explores the feasibility of using heat pipes as heat exchangers inside an absorption heat pump type II (Absorption Heat Transformer) of a thermal capacity of 0.7kW. The heat pipe is a passive device to transfer heat because of low thermal resistance. A heat exchanger with heat pipes can be integrated between the condensation and evaporation processes of an Absorption Heat Transformer. This study has demonstrated that seven commercial heat pipes are required to condense 0.714kW and to reuse 0.177kW at 60°C in the evaporator, representing almost a third part of total heat supplied without heat pipes, provided that the generator temperature is over 55°C. Therefore, the efficiency of the Absorption Heat Transformer can be improved based on the concept of the Coefficient of Performance up to 20%.
High operating temperatures in engines produce a thermal degradation promoting the oil oxidation that affects its tribological performance. In this paper, an alternative method is proposed to ...simulate engine oil degradation by mixing degraded oil with fresh oil to simulate a mileage. The simulated and real degraded engine oils were compared by infrared spectroscopy analysis. The dynamic viscosities of mixed oils were measured by a rheometer at 50 °C and 80 °C and a block-on-ring tribometer was used to evaluate their tribological performance under mixed lubrication regime at these two temperatures. The results showed that the simulated degradation is acceptable, the coefficient of friction decreased at higher temperature and reduced as the engine oil is close to its end of service life.
•Mixing degraded and fresh oils: An alternative to simulate engine oil degradation.•FT-IR analysis showed this method is effective for simulating degradation process.•Tribological performance of simulated degraded oils was investigated.•At elevated temperatures, friction coefficient and dynamic viscosity decreases.•As the engine oil is near the end of its service life, friction coefficient decreases.
The inspection and maintenance of drains with varying heights necessitates a drain mapping robot with trained labour to maintain community hygiene and prevent the spread of diseases. For adapting to ...level changes and navigating in the narrow confined environments of drains, we developed a self-configurable hybrid robot, named Tarantula-II. The platform is a quadruped robot with hybrid locomotion and the ability to reconfigure to achieve variable height and width. It has four legs, and each leg is made of linear actuators and modular rolling wheel mechanisms with bi-directional movement. The platform has a fuzzy logic system for collision avoidance of the side wall in the drain environment. During level shifting, the platform achieves stability by using the pitch angle as the feedback from the inertial measuring unit (IMU) mounted on the platform. This feedback helps to adjust the accurate height of the platform. In this paper, we describe the detailed mechanical design and system architecture, kinematic models, control architecture, and stability of the platform. We deployed the platform both in a lab setting and in a real-time drain environment to demonstrate the wall collision avoidance, stability, and level shifting capabilities of the platform.
Blue maize is an excellent source of bioactive components such as phenolic acids and anthocyanins but when it is processed for human consumption, these compounds decrease considerably. Therefore, ...blue maize could be directed to produce nutraceutical extracts. The aim of this study was to evaluate the relation between anthocyanins composition of acidified and non-acidified extracts from native and hybrid blue maize genotypes and their antiproliferative effect in mammary (MCF7), liver (HepG2), colon (Caco2 and HT29) and prostate (PC3) cancer cells. The most abundant phenolic acid was ferulic acid. Nine anthocyanins were quantified in the extracts, being Cy3-Glu the most abundant. Acylated forms were also obtained in high abundance depending of the extraction method. An extract concentration range of 4.31 to 7.23 mg/mL inhibited by 50 % the growth of untransformed cells NIH3T3. Antiproliferative effect on PC3, Caco2, HepG2 and MCF7 cancer cells of acidified extracts from hybrid blue maize was larger than the observed using non-acidified extracts. Among the nine compounds that were quantified in the extracts tested, CyMalGlu I showed the strongest correlation with the reduction of cell viability in Caco2 (−0.876), HepG2 (−0.813), MCF7 (−0.765) and PC3 (−0.894). No significant correlation or differences in antiproliferative effect on HT29 was found among the extracts. The method of extraction of maize anthocyanins must be selected to obtain a high yield of CyMalGlu I more than only Cy3-Glu since acylation affects the inhibition of cancer cell growth.
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