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  • 1
    Electronic Resource
    Electronic Resource
    A density functional theory study of CO oxidation on Ru(0001) at low coverage (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 10564-10570 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have performed ab initio density functional theory calculations with the generalized gradient approximation to investigate CO oxidation on Ru(0001). Several reaction pathways and transition states are identified. A much higher reaction barrier compared to that on Pt(111) is determined, confirming that the Ru is very inactive for CO oxidation under UHV conditions. The origin of the reaction barrier was analyzed. It is found that in the transition state the chemisorbed O atom sits in an unfavorable bonding site and a significant competition for bonding with the same substrate atoms occurs between the CO and the chemisorbed O, resulting in the high barrier. Ab initio molecular dynamics calculations show that the activation of the chemisorbed O atom from the initial hcp hollow site (the most stable site) to the bridge site is the crucial step for the reaction. The CO oxidation on Ru(0001) via the Eley–Rideal mechanism has also been investigated. A comparison with previous theoretical work has been made. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481690
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  • 2
    Electronic Resource
    Electronic Resource
    The possibility of single C–H bond activation in CH4 on a MoO3-supported Pt catalyst: A density functional theory study (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 4281-4285 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Methane activation is a crucial step in the conversion of methane to valuable oxygenated products. In heterogeneous catalysis, however, methane activation often leads to complete dissociation: If a catalyst can activate the first C–H bond in CH4, it can often break the remaining C–H bonds. In this study, using density functional theory, we illustrate that single C–H bond activation in CH4 is possible. We choose a model system which consists of isolated Pt atoms on a MoO3(010) surface. We find that the Pt atoms on this surface can readily activate the first C–H bond in methane. The reaction barrier of only 0.3 eV obtained in this study is significantly lower than that on a Pt(111) surface. We also find, in contrast to the processes on pure metal surfaces, that the further dehydrogenation of methyl (CH3) is very energetically unfavorable on the MoO3-supported Pt catalyst. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1449942
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  • 3
    Electronic Resource
    Electronic Resource
    Methane transformation to carbon and hydrogen on Pd(100): Pathways and energetics from density functional theory calculations (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 322-327 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Density functional theory with gradient corrections has been employed to study the reaction pathways and the reaction energetics for the transformations of CH4 to C and H on a Pd(100) surface. On examination of transition state structures identified in each elementary reaction, a clear relationship between the valencies of the CHx fragments and the locations of the transition states emerges. The higher the valency of the CHx fragment, the higher the coordination number of the CHx with the surface atoms. The calculated reaction energetics are in good agreement with the experiments. In addition, calculation results are also used to illustrate an interesting issue concerning the CH3 stability on Pd surfaces. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1423663
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  • 4
    Electronic Resource
    Electronic Resource
    A density functional theory study of carbon monoxide oxidation on the Cu3Pt(111) alloy surface: Comparison with the reactions on Pt(111) and Cu(111) (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 5272-5277 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Alloying metals is often used as an effective way to enhance the reactivity of surfaces. Aiming to shed light on the effect of alloying on reaction mechanisms, we carry out a comparative study of CO oxidation on Cu3Pt(111), Pt(111), and Cu(111) by means of density functional theory calculations. Alloying effects on the bonding sites and bonding energies of adsorbates, and the reaction pathways are investigated. It is shown that CO preferentially adsorbs on an atop site of Pt and O preferentially adsorbs on a fcc hollow site of three Cu atoms on Cu3Pt(111). It is also found that the adsorption energies of CO (or Oa) decreases on Pt (or Cu) on the alloy surface with respect to those on pure metals. More importantly, having identified the transition states for CO oxidation on those three surfaces, we found an interesting trend for the reaction barrier on the three surfaces. Similar to the adsorption energies, the reaction barrier on Cu3Pt possesses an intermediate value of those on pure Pt and Cu metals. The physical origin of these results has been analyzed in detail. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1395626
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  • 5
    Electronic Resource
    Electronic Resource
    Insight into electron-mediated reaction mechanisms: Catalytic CO oxidation on a ruthenium surface (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 8113-8118 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ruthenium is one of the poorest catalysts for CO oxidation under normal conditions (low or medium O coverage and normal temperature). However, a recent study [Science 285, 1042 (1999)] reveals that, under femtosecond laser irradiation, CO2 can be formed on the Ru surface, and the reaction follows an electron-mediated mechanism. We carried out density functional theory calculations to investigate CO oxidation via an electron-mediated mechanism on Ru(0001). By comparison to the reaction under normal conditions, following features emerge in the electron-mediated mechanism: (i) more reaction channels are open; (ii) the reaction barrier is significantly lowered. The physical origins for these novel features have been analyzed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1365150
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  • 6
    Electronic Resource
    Electronic Resource
    A first principles study of methanol decomposition on Pd(111): Mechanisms for O–H bond scission and C–O bond scission (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 7182-7186 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: There is some dispute as to whether methanol decomposition occurs by O–H bond scission or C–O bond scission. By carrying out density functional theory calculations, we investigate both scenario of the reaction pathways of methanol decomposition on a Pd(111) surface. It is shown that the O–H bond scission pathway is much more energetically favorable than the C–O bond scission pathway. The high reaction barrier in the latter case is found to be due to the poor bonding abilities of CH3 and OH with the surface at the reaction sites. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1405157
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  • 7
    Electronic Resource
    Electronic Resource
    The internal concentration of K^+ in isolated rat liver mitochondria
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Bioenergetics 806 (1985), S. 272-276 
    Details
    ISSN: 0005-2728
    Keywords: (Rat liver mitochondria) ; Centrifugation ; K^+ ; Sucrose-space hypothesis
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0005-2728(85)90105-7
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  • 8
    Electronic Resource
    Electronic Resource
    Ab initio calculation of natural hybrid orbitals
    Amsterdam : Elsevier
    Journal of Molecular Structure: THEOCHEM 313 (1994), S. 231-236 
    Details
    ISSN: 0166-1280
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0166-1280(94)03705-P
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  • 9
    Electronic Resource
    Electronic Resource
    Ab initio calculation of natural hybrid orbitals
    Amsterdam : Elsevier
    Journal of Molecular Structure: THEOCHEM 313 (1994), S. 231-236 
    Details
    ISSN: 0166-1280
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0166-1280(94)85005-4
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  • 10
    Electronic Resource
    Electronic Resource
    Changes in Nuclear Ultrastructure during Callus Development in Tissue Culture of Allium Sativum (1998)
    Springer
    Biologia plantarum 41 (1998), S. 49-55 
    Details
    ISSN: 1573-8264
    Keywords: active phase cells ; dividing cells ; garlic ; nucleolus ; quiescent cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The changes in nuclear ultrastructure during garlic development were investigated. In quiescent cells, the nucleus was oblate and small, full of heterochromatin, and without nucleolus. In the active phase cells, the nucleus moved toward the center of the cell, and was enlarged with many deep fissures, and the heterochromatin in the nucleus turned to be euchromatin. One or more nucleoli were seen in active phase cells. Cell divisions were by means of amitosis. Relatively large nuclei with small distortions were seen in the callus cells. These results suggest that the metabolism of the active cells was higher than that of callus and quiescent cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1001752214563
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