51
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Xiong H, Schwartz TJ, Andersen NI, Dumesic JA, Datye AK. Graphitic-Carbon Layers on Oxides: Toward Stable Heterogeneous Catalysts for Biomass Conversion Reactions. Angew Chem Int Ed Engl 2015; 54:7939-43. [DOI: 10.1002/anie.201502206] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Indexed: 11/05/2022]
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52
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Xiong H, DeLaRiva A, Wang Y, Datye AK. Low-temperature aqueous-phase reforming of ethanol on bimetallic PdZn catalysts. Catal Sci Technol 2015. [DOI: 10.1039/c4cy00914b] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Bimetallic PdZn catalysts supported on carbon black (CB) and carbon nanotubes (CNTs) were found to be selective for CO-free H2 production from ethanol at low temperature (250 °C).
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53
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Peterson EJ, DeLaRiva AT, Lin S, Johnson RS, Guo H, Miller JT, Hun Kwak J, Peden CHF, Kiefer B, Allard LF, Ribeiro FH, Datye AK. Low-temperature carbon monoxide oxidation catalysed by regenerable atomically dispersed palladium on alumina. Nat Commun 2014; 5:4885. [DOI: 10.1038/ncomms5885] [Citation(s) in RCA: 433] [Impact Index Per Article: 43.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Accepted: 08/02/2014] [Indexed: 12/26/2022] Open
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54
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Davidson SD, Sun J, Hong Y, Karim AM, Datye AK, Wang Y. The effect of ZnO addition on Co/C catalyst for vapor and aqueous phase reforming of ethanol. Catal Today 2014. [DOI: 10.1016/j.cattod.2013.12.044] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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55
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Zhang H, Sun J, Dagle VL, Halevi B, Datye AK, Wang Y. Influence of ZnO Facets on Pd/ZnO Catalysts for Methanol Steam Reforming. ACS Catal 2014. [DOI: 10.1021/cs500590t] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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56
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Carrillo C, Johns TR, Xiong H, DeLaRiva A, Challa SR, Goeke RS, Artyushkova K, Li W, Kim CH, Datye AK. Trapping of Mobile Pt Species by PdO Nanoparticles under Oxidizing Conditions. J Phys Chem Lett 2014; 5:2089-93. [PMID: 26270497 DOI: 10.1021/jz5009483] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Pt is an active catalyst for diesel exhaust catalysis but is known to sinter and form large particles under oxidizing conditions. Pd is added to improve the performance of the Pt catalysts. To investigate the role of Pd, we introduced metallic Pt nanoparticles via physical vapor deposition to a sample containing PdO nanoparticles. When the catalyst was aged in air, the Pt particles disappeared, and the Pt was captured by the PdO, forming bimetallic Pt-Pd nanoparticles. The formation of metallic Pt-Pd alloys under oxidizing conditions is indeed remarkable but is consistent with bulk thermodynamics. The results show that mobile Pt species are effectively trapped by PdO, representing a novel mechanism by which Ostwald ripening is slowed down. The results have implications for the development of sinter-resistant catalysts and help explain the improved performance and durability of Pt-Pd in automotive exhaust catalytic converters.
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DeLaRiva AT, Hansen TW, Challa SR, Datye AK. In situ Transmission Electron Microscopy of catalyst sintering. J Catal 2013. [DOI: 10.1016/j.jcat.2013.08.018] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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58
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Agarwal S, Lefferts L, Mojet BL, Ligthart DAJM, Hensen EJM, Mitchell DRG, Erasmus WJ, Anderson BG, Olivier EJ, Neethling JH, Datye AK. Exposed surfaces on shape-controlled ceria nanoparticles revealed through AC-TEM and water-gas shift reactivity. CHEMSUSCHEM 2013; 6:1898-1906. [PMID: 24108516 DOI: 10.1002/cssc.201300651] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Indexed: 06/02/2023]
Abstract
Aberration-corrected transmission electron microscopy and high-angle annular dark field imaging was used to investigate the surface structures and internal defects of CeO2 nanoparticles (octahedra, rods, and cubes). Further, their catalytic reactivity in the water-gas shift (WGS) reaction and the exposed surface sites by using FTIR spectroscopy were tested. Rods and octahedra expose stable (111) surfaces whereas cubes have primarily (100) facets. Rods also had internal voids and surface steps. The exposed planes are consistent with observed reactivity patterns, and the normalized WGS reactivity of octahedra and rods were similar, but the cubes were more reactive. In situ FTIR spectroscopy showed that rods and octahedra exhibit similar spectra for -OH groups and that carbonates and formates formed upon exposure to CO whereas for cubes clear differences were observed. These results provide definitive information on the nature of the exposed surfaces in these CeO2 nanostructures and their influence on the WGS reactivity.
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Hansen TW, DeLaRiva AT, Challa SR, Datye AK. Sintering of catalytic nanoparticles: particle migration or Ostwald ripening? Acc Chem Res 2013; 46:1720-30. [PMID: 23634641 DOI: 10.1021/ar3002427] [Citation(s) in RCA: 521] [Impact Index Per Article: 47.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Metal nanoparticles contain the active sites in heterogeneous catalysts, which are important for many industrial applications including the production of clean fuels, chemicals and pharmaceuticals, and the cleanup of exhaust from automobiles and stationary power plants. Sintering, or thermal deactivation, is an important mechanism for the loss of catalyst activity. This is especially true for high temperature catalytic processes, such as steam reforming, automotive exhaust treatment, or catalytic combustion. With dwindling supplies of precious metals and increasing demand, fundamental understanding of catalyst sintering is very important for achieving clean energy and a clean environment, and for efficient chemical conversion processes with atom selectivity. Scientists have proposed two mechanisms for sintering of nanoparticles: particle migration and coalescence (PMC) and Ostwald ripening (OR). PMC involves the mobility of particles in a Brownian-like motion on the support surface, with subsequent coalescence leading to nanoparticle growth. In contrast, OR involves the migration of adatoms or mobile molecular species, driven by differences in free energy and local adatom concentrations on the support surface. In this Account, we divide the process of sintering into three phases. Phase I involves rapid loss in catalyst activity (or surface area), phase II is where sintering slows down, and phase III is where the catalyst may reach a stable performance. Much of the previous work is based on inferences from catalysts that were observed before and after long term treatments. While the general phenomena can be captured correctly, the mechanisms cannot be determined. Advancements in the techniques of in situ TEM allow us to observe catalysts at elevated temperatures under working conditions. We review recent evidence obtained via in situ methods to determine the relative importance of PMC and OR in each of these phases of catalyst sintering. The evidence suggests that, in phase I, OR is responsible for the rapid loss of activity that occurs when particles are very small. Surprisingly, very little PMC is observed in this phase. Instead, the rapid loss of activity is caused by the disappearance of the smallest particles. These findings are in good agreement with representative atomistic simulations of sintering. In phase II, sintering slows down since the smallest particles have disappeared. We now see a combination of PMC and OR, but do not fully understand the relative contribution of each of these processes to the overall rates of sintering. In phase III, the particles have grown large and other parasitic phenomena, such as support restructuring, can become important, especially at high temperatures. Examining the evolution of particle size and surface area with time, we do not see a stable or equilibrium state, especially for catalysts operating at elevated temperatures. In conclusion, the recent literature, especially on in situ studies, shows that OR is the dominant process causing the growth of nanoparticle size. Consequently, this leads to the loss of surface area and activity. While particle migration could be controlled through suitable structuring of catalyst supports, it is more difficult to control the mobility of atomically dispersed species. These insights into the mechanisms of sintering could help to develop sinter-resistant catalysts, with the ultimate goal of designing catalysts that are self-healing.
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Johns TR, Gaudet JR, Peterson EJ, Miller JT, Stach EA, Kim CH, Balogh MP, Datye AK. Microstructure of Bimetallic PtPd Catalysts under Oxidizing Conditions. ChemCatChem 2013. [DOI: 10.1002/cctc.201300181] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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61
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Xiong H, Pham HN, Datye AK. A facile approach for the synthesis of niobia/carbon composites having improved hydrothermal stability for aqueous-phase reactions. J Catal 2013. [DOI: 10.1016/j.jcat.2013.03.007] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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62
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Sun J, Mei D, Karim AM, Datye AK, Wang Y. Cover Picture: Minimizing the Formation of Coke and Methane on Co Nanoparticles in Steam Reforming of Biomass-Derived Oxygenates (ChemCatChem 6/2013). ChemCatChem 2013. [DOI: 10.1002/cctc.201390024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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63
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Xiong H, Wang T, Shanks BH, Datye AK. Tuning the Location of Niobia/Carbon Composites in a Biphasic Reaction: Dehydration of d-Glucose to 5-Hydroxymethylfurfural. Catal Letters 2013. [DOI: 10.1007/s10562-013-1004-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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64
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Gaudet JR, de la Riva A, Peterson EJ, Bolin T, Datye AK. Improved Low-Temperature CO Oxidation Performance of Pd Supported on La-Stabilized Alumina. ACS Catal 2013. [DOI: 10.1021/cs400024u] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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65
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Sun J, Mei D, Karim AM, Datye AK, Wang Y. Minimizing the Formation of Coke and Methane on Co Nanoparticles in Steam Reforming of Biomass-Derived Oxygenates. ChemCatChem 2013. [DOI: 10.1002/cctc.201300041] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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66
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Johnson RS, DeLaRiva A, Ashbacher V, Halevi B, Villanueva CJ, Smith GK, Lin S, Datye AK, Guo H. The CO oxidation mechanism and reactivity on PdZn alloys. Phys Chem Chem Phys 2013; 15:7768-76. [DOI: 10.1039/c3cp00126a] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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67
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Pham HN, Anderson AE, Johnson RL, Schmidt-Rohr K, Datye AK. Improved Hydrothermal Stability of Mesoporous Oxides for Reactions in the Aqueous Phase. Angew Chem Int Ed Engl 2012; 51:13163-7. [DOI: 10.1002/anie.201206675] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2012] [Revised: 10/16/2012] [Indexed: 11/10/2022]
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68
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Pham HN, Anderson AE, Johnson RL, Schmidt-Rohr K, Datye AK. Improved Hydrothermal Stability of Mesoporous Oxides for Reactions in the Aqueous Phase. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201206675] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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69
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Benavidez AD, Kovarik L, Genc A, Agrawal N, Larsson EM, Hansen TW, Karim AM, Datye AK. Environmental Transmission Electron Microscopy Study of the Origins of Anomalous Particle Size Distributions in Supported Metal Catalysts. ACS Catal 2012. [DOI: 10.1021/cs3005117] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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70
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Matos J, Ono LK, Behafarid F, Croy JR, Mostafa S, DeLaRiva AT, Datye AK, Frenkel AI, Roldan Cuenya B. In situ coarsening study of inverse micelle-prepared Pt nanoparticles supported on γ-Al2O3: pretreatment and environmental effects. Phys Chem Chem Phys 2012; 14:11457-67. [PMID: 22801490 DOI: 10.1039/c2cp41339f] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The thermal stability of inverse micelle prepared Pt nanoparticles (NPs) supported on nanocrystalline γ-Al(2)O(3) was monitored in situ under different chemical environments (H(2), O(2), H(2)O) via extended X-ray absorption fine-structure spectroscopy (EXAFS) and ex situ via scanning transmission electron microscopy (STEM). Drastic differences in the stability of identically synthesized NP samples were observed upon exposure to two different pre-treatments. In particular, exposure to O(2) at 400 °C before high temperature annealing in H(2) (800 °C) was found to result in the stabilization of the inverse micelle prepared Pt NPs, reaching a maximum overall size after moderate coarsening of ∼1 nm. Interestingly, when an analogous sample was pre-treated in H(2) at ∼400 °C, a final size of ∼5 nm was reached at 800 °C. The beneficial role of oxygen in the stabilization of small Pt NPs was also observed in situ during annealing treatments in O(2) at 450 °C for several hours. In particular, while NPs of 0.5 ± 0.1 nm initial average size did not display any significant sintering (0.6 ± 0.2 nm final size), an analogous thermal treatment in hydrogen leads to NP coarsening (1.2 ± 0.3 nm). The same sample pre-dosed and annealed in an atmosphere containing water only displayed moderate sintering (0.8 ± 0.3 nm). Our data suggest that PtO(x) species, possibly modifying the NP/support interface, play a role in the stabilization of small Pt NPs. Our study reveals the enhanced thermal stability of inverse micelle prepared Pt NPs and the importance of the sample pre-treatment and annealing environment in the minimization of undesired sintering processes affecting the catalytic performance of nanosized particles.
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Halevi B, Peterson EJ, Roy A, DeLariva A, Jeroro E, Gao F, Wang Y, Vohs JM, Kiefer B, Kunkes E, Hävecker M, Behrens M, Schlögl R, Datye AK. Catalytic reactivity of face centered cubic PdZnα for the steam reforming of methanol. J Catal 2012. [DOI: 10.1016/j.jcat.2012.04.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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72
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Wei Z, Sun J, Li Y, Datye AK, Wang Y. Bimetallic catalysts for hydrogen generation. Chem Soc Rev 2012; 41:7994-8008. [DOI: 10.1039/c2cs35201j] [Citation(s) in RCA: 260] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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73
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Challa SR, Delariva AT, Hansen TW, Helveg S, Sehested J, Hansen PL, Garzon F, Datye AK. Relating Rates of Catalyst Sintering to the Disappearance of Individual Nanoparticles during Ostwald Ripening. J Am Chem Soc 2011; 133:20672-5. [DOI: 10.1021/ja208324n] [Citation(s) in RCA: 209] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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74
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Lebarbier VM, Karim AM, Engelhard MH, Wu Y, Xu BQ, Petersen EJ, Datye AK, Wang Y. The effect of zinc addition on the oxidation state of cobalt in Co/ZrO2 catalysts. CHEMSUSCHEM 2011; 4:1679-1684. [PMID: 21919212 DOI: 10.1002/cssc.201100240] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Indexed: 05/31/2023]
Abstract
The effect of zinc promotion on the oxidation state of cobalt in Co/ZrO(2) catalysts was investigated and correlated with the activity and selectivity for ethanol steam reforming (ESR). Catalysts were synthesized by applying incipient wetness impregnation and characterized by using Brunauer-Emmett-Teller (BET), temperature-programmed reduction (TPR) measurements, X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Higher ethanol conversion and lower CH(4) selectivity are observed for the Co/ZrO(2) catalyst promoted with Zn as compared to the Co/ZrO(2) catalyst alone. Addition of Zn inhibits the oxidation of metallic cobalt (Co(0) ) particles and results in a higher ratio of Co(0) /Co(2+) in the Zn-promoted Co/ZrO(2) catalyst. These results suggest that metallic cobalt (Co(0) ) is more active than Co(2+) in the ethanol conversion through dehydrogenation and that Co(2+) may play a role in the CH(4) formation. TPR measurements, on the other hand, reveal that Zn addition inhibits the reduction of Co(2+) and Co(3+) , which would lead to the false conclusion that oxidized Co is required to reduce the CH(4) formation. Therefore, TPR measurements may not be appropriate to correlate the degree of metal reducibility (in this case Co(0)) with the catalyst activity for reactions, such as ESR, where oxidizing conditions exist.
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Pagán-Torres YJ, Gallo JMR, Wang D, Pham HN, Libera JA, Marshall CL, Elam JW, Datye AK, Dumesic JA. Synthesis of Highly Ordered Hydrothermally Stable Mesoporous Niobia Catalysts by Atomic Layer Deposition. ACS Catal 2011. [DOI: 10.1021/cs200367t] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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