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排序方式: 共有1235条查询结果,搜索用时 31 毫秒
61.
Santosh K. Gupta Maya Abdou Partha S. Ghosh Jose P. Zuniga Ezhilarasan Manoharan HyeongJun Kim Yuanbing Mao 《Journal of the American Ceramic Society》2020,103(1):235-248
Unveiling the underlying mechanisms of properties of functional materials, including the luminescence differences among similar pyrochlores A2B2O7, opens new gateways to select proper hosts for various optoelectronic applications by scientists and engineers. For example, although La2Zr2O7 (LZO) and La2Hf2O7 (LHO) pyrochlores have similar chemical compositional and crystallographic structural features, they demonstrate different luminescence properties both before and after doped with Eu3+ ions. Based on our earlier work, LHO-based nanophosphors display higher photo- and radioluminescence intensity, higher quantum efficiency, and longer excited state lifetime compared to LZO-based nanophosphors. Moreover, under electronic O2−→Zr4+/Hf4+ transition excitation at 306 nm, undoped LHO nanoparticles (NPs) have only violet blue emission, whereas LZO NPs show violet blue and red emissions. In this study, we have combined experimental and density functional theory (DFT) based theoretical calculation to explain the observed results. First, we calculated the density of state (DOS) based on DFT and studied the energetics of ionized oxygen vacancies in the band gaps of LZO and LHO theoretically, which explain their underlying luminescence difference. For Eu3+-doped NPs, we performed emission intensity and lifetime calculations and found that the LHOE NPs have higher host to dopant energy transfer efficiency than the LZOE NPs (59.3% vs 24.6%), which accounts for the optical performance superiority of the former over the latter. Moreover, by corroborating our experimental data with the DFT calculations, we suggest that the Eu3+ doping states in LHO present at exact energy position (both in majority and minority spin components) where oxygen defect states are located unlike those in LZO. Lastly, both the NPs show negligible photobleaching highlighting their potential for bioimaging applications. This current report provides a deeper understanding of the advantages of LHO over LZO as an advanced host for phosphors, scintillators, and fluoroimmunoassays. 相似文献
62.
Mathematical models for single electrode reversible heat and non-isothermal electromotive force (EMF) of a solid oxide fuel cell (SOFC) are developed. These models estimate the volumetric reversible heat generation and EMF of electrochemical reactions, within each electrode at local conditions of temperature and pressure, based on entropy change of half reactions. The resulting equations are thermodynamically consistent. They inherently obey the conservation of energy law as the electrochemical energy released added to the heat of reactions at each electrode equate the enthalpy change of the reacted species. The equations are implemented to model electrodes in a tubular micro- solid oxide fuel cell (TμSOFC). The thermodynamic consistency of the model is numerically confirmed as the enthalpy of the reactants equates the electric energy released by the cell plus the sum of electrode heats plus electrolyte Ohmic heat. The effect of thermal gradients on the cell's overall EMF is found to be negligible. The reversible and irreversible heat generation of each electrode are distinguished. Overall, the anode is found to be endothermic, and the cathode exothermic. 相似文献
63.
Henrique AL Ribeiro Luis Sordo Vieira Yogesh Scindia Bandita Adhikari Matthew Wheeler Adam Knapp William Schroeder Borna Mehrad Reinhard Laubenbacher 《Journal of the Royal Society Interface》2022,19(189)
Aspergillus species are ubiquitous environmental moulds, with spores inhaled daily by most humans. Immunocompromised hosts can develop an invasive infection resulting in high mortality. There is, therefore, a pressing need for host-centric therapeutics for this infection. To address it, we created a multi-scale computational model of the infection, focused on its interaction with the innate immune system and iron, a critical nutrient for the pathogen. The model, parameterized using published data, was found to recapitulate a wide range of biological features and was experimentally validated in vivo. Conidial swelling was identified as critical in fungal strains with high growth, whereas the siderophore secretion rate seems to be an essential prerequisite for the establishment of the infection in low-growth strains. In immunocompetent hosts, high growth, high swelling probability and impaired leucocyte activation lead to a high conidial germination rate. Similarly, in neutropenic hosts, high fungal growth was achieved through synergy between high growth rate, high swelling probability, slow leucocyte activation and high siderophore secretion. In summary, the model reveals a small set of parameters related to fungal growth, iron acquisition and leucocyte activation as critical determinants of the fate of the infection. 相似文献
64.
65.
This study evaluated the efficacy of ultrasound treatment and nano-zinc oxide (ZnO) coating individually and in combination in preserving the quality of fresh-cut kiwifruit. The nano-ZnO coating solution was prepared by mixing the ZnO nanoparticles in premixed chitosan–acetic acid solution. The fresh-cut kiwifruit were dipped in NaClO solution (50 μL?L?1 sodium, control), subjected to ultrasound treatment (40 KHz, 350 W, 10 min), or coated with nano-ZnO solution. The fresh-cut kiwifruit samples were also subjected to combined ultrasound treatment and nano-ZnO coating. All of these test samples were stored at 4 °C for 10 days. The effects of these treatments on the quality parameters such as the production of carbon dioxide and ethylene, mass loss, and flesh firmness were investigated. At the end of storage, the combination treatments with ultrasound treatment at 40 KHz with 1.2 g?L?1 nano-ZnO coating showed lower production of ethylene (1.86 μL?kg?1?h?1) and carbon dioxide (10.01 mg?kg?1?h?1), water loss (0.46 %), and texture (7.87 N). Hence, it was concluded that the combination of ultrasound treatment with nano-ZnO coating is a promising approach to extend the shelf-life of fresh-cut kiwifruit. 相似文献
66.
An infrared spectroscopy study of lipid adsorption from hexane onto an acid-activated bleaching clay
C. Adhikari A. Proctor G. D. Blyholder 《Journal of the American Oil Chemists' Society》1997,74(10):1265-1268
The mode of adsorption of oleic acid (OA) (0.05 M), triglyceride (TG) (0.05 M) and phosphatidylcholine (PC) (0.5 mM) from
hexane solution onto 0.5 g of an acid-activated bleaching clay was investigated using diffuse reflectance Fourier transform
infrared spectroscopy. OA was mostly weakly adsorbed by bound water, with some OA adsorbed to silanol sites through carboxyl
carbonyl groups. TG was hydrogen- bonded to surface silanol groups through ester carbonyl groups. The CH2 stretches indicated that TG was oriented perpendicular or at an angle to the surface. PC phosphate groups were bound by the
surface moisture with little interaction with silanol groups. The adsorption mechanism of these lipids contrasts with the
adsorption of carotenoid and chlorophyll under the same conditions. These pigments are bound by chemisorption, with catalytic
modification often occurring before adsorption. 相似文献
67.
Ultrahigh temperature water gas shift catalysts to increase hydrogen yield from biomass gasification 总被引:1,自引:0,他引:1
Noble metal (Rh, Pt, Pd, Ir, Ru, and Ag) and Ni catalysts supported on CeO2–Al2O3 were investigated for water gas shift reaction at ultrahigh temperatures. Pt/CeO2–Al2O3 and Ru/CeO2–Al2O3 demonstrated as the best catalysts in terms of activity, hydrogen yield and hydrogen selectivity. At 700 °C and steam to CO ratio of 5.2:1, Pt/CeO2–Al2O3 converted 76.3% of CO with 94.7% of hydrogen selectivity. At the same conditions, the activity and hydrogen selectivity for Ru/CeO2–Al2O3 were 63.9% and 85.6%, respectively. Both catalysts showed a good stability over 9 h of continuous operation. However, both catalysts showed slight deactivation during the test period. The study revealed that Pt/CeO2–Al2O3 and Ru/CeO2–Al2O3 were excellent ultrahigh temperature water gas shift catalysts, which can be coupled with biomass gasification in a downstream reactor. 相似文献
68.
Swetapadma PANDA Nikhil P. ZADE Pradip SARKAR Robin DAVIS 《Frontiers of Structural and Civil Engineering》2022,16(1):117-130
Proven research output on the behavior of structures made of waste copper slag concrete can improve its utilization in the construction industry and thereby help to develop a sustainable built environment. Although numerous studies on waste copper slag concrete can be found in the published literature, no research has focused on the structural application of this type of concrete. In particular, the variability in the strength properties of waste copper slag concrete, which is required for various structural applications, such as limit state design formulation, reliability-based structural analysis, etc., has so far not attracted the attention of researchers. This paper quantifies the uncertainty associated with the compressive-, flexural- and split tensile strength of hardened concrete with different dosages of waste copper slag as fine aggregate. Best-fit probability distribution models are proposed based on statistical analyses of strength data generated from laboratory experiments. In addition, the paper presents a reliability-based seismic risk assessment of a typical waste copper slag incorporated reinforced concrete framed building, considering the proposed distribution model. The results show that waste copper slag can be safely used for seismic resistant structures as it results in an identical probability of failure and dispersion in the drift demand when compared with a conventional concrete building made of natural sand. 相似文献
69.
70.
In this paper, a fast yet accurate CMOS analog circuit sizing method, referred to as Iterative Sequential Geometric Programming (ISGP), has been proposed. In this methodology, a correction factor has been introduced for each parameter of the geometric programming (GP) compatible device and performance model. These correction factors are updated using a SPICE simulation after every iteration of a sequential geometric programming (SGP) optimization. The proposed methodology takes advantage of SGP based optimization, namely, fast convergence and effectively optimum design and at the same time it uses SPICE simulation to fine tune the design point by rectifying inaccuracy that may exists in the GP compatible device and performance models. In addition, the ISGP considers the requirement of common centroid layout and yield aware design centering for robust final design point specifying the number of fingers and finger widths for each transistor which makes the design point ready for layout. 相似文献